Дилантин инструкция по применению

phenytoin will decrease the level or effect of abemaciclib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of abemaciclib with strong CYP3A4 inducers reduces plasma concentration of abemaciclib and its metabolites.

phenytoin will decrease the level or effect of abrocitinib by increasing metabolism. Avoid or Use Alternate Drug. Abrocitinib is a CYP2C9 and CYP2C19 substrate. Drugs that are strong inducers of CYP2C19 or CYP2C9 decreases the combined exposure of abrocitinib and its active metabolites, resulting in loss of or reduced clinical response.

phenytoin will decrease the level or effect of acalabrutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of acalabrutinib with strong CYP3A inducers. If a strong CYP3A inducer must be used, increase acalabrutinib dose to 200 mg twice daily.

phenytoin decreases levels of acoramidis by increasing metabolism. Avoid or Use Alternate Drug. Acoramidis is metabolized by UGT enzyme-mediated glucuronidation. Coadministration with UGT inducers can potentially decrease acoramidis exposure. .phenytoin decreases levels of acoramidis by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Although acoramidis is not metabolized by CYP3A, strong CYP3A inducers can induce UGT enzymes (acoramidis is metabolized by UGT glucuronidation).

phenytoin will decrease the level or effect of adagrasib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.adagrasib will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of adagrasib, a CYP2C9 inhibitor, with sensitive CYP2C9 substrates unless otherwise recommended in the prescribing information for these substrates.

phenytoin decreases levels of afatinib by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Increase afatinib daily dose by 10 mg as tolerated if chronic therapy with P-gp inducer required; resume previous afatinib dose 2-3 days after P-gp inducer discontinued.

phenytoin will decrease the level or effect of alpelisib by pharmacodynamic synergism. Avoid or Use Alternate Drug. Avoid coadministration of alpelisib (CYP3A4 substrate) with strong CYP3A4 inducers.phenytoin will decrease the level or effect of alpelisib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

apalutamide will decrease the level or effect of phenytoin by affecting hepatic enzyme CYP2C19 metabolism. Avoid or Use Alternate Drug. Coadministration of apalutamide, a strong CYP2C19 inducer, with drugs that are CYP2C19 substrates can result in lower exposure to these medications. Avoid or substitute another drug for these medications when possible. Evaluate for loss of therapeutic effect if medication must be coadministered.

phenytoin will decrease the level or effect of apremilast by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration with strong CYP inducers results in a significant decrease of systemic exposure of apremilast, which may result in loss of efficacy

phenytoin decreases levels of atrasentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration with strong or moderate CYP3A inducers is expected to decrease atrasentan systemic exposure, which may decrease efficacy. .

phenytoin will decrease the level or effect of avapritinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin decreases levels of axitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Selection of concomitant medication with no or minimal CYP3A4 induction potential is recommended.

phenytoin will decrease the level or effect of bedaquiline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of bedaquiline with strong CYP3A4 inducers due to potential for decreased therapeutic effect

phenytoin will decrease the level or effect of bictegravir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of strong CYP3A and UGT1A1 inducers can substantially decrease bictegravir plasma concentrations. This may result in the loss of therapeutic effect and development of resistance to bictegravir. Coadministration with another anticonvulsant should be considered.

phenytoin decreases levels of bosutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong CYP3A4 inducers decreased bosutinib plasma concentration by ~85%.

bremelanotide will decrease the level or effect of phenytoin by Other (see comment). Avoid or Use Alternate Drug. Bremelanotide may slow gastric emptying and potentially reduces the rate and extent of absorption of concomitantly administered oral medications. Avoid use when taking any oral drug that is dependent on threshold concentrations for efficacy. Interactions listed are representative examples and do not include all possible clinical examples.

phenytoin will decrease the level or effect of brigatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration with strong CYP3A4 inducers may decrease brigatinib efficacy.

phenytoin will decrease the level or effect of cabozantinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of cabozantinib with strong CYP3A4 inducers. If a strong CYP3A4 inducer is required, increase cabozantinib dose by 40 mg/day (Cometriq) or by 20 mg/day (Cabometyx). Resume previous dose 2-3 days after strong CYP3A4 inducer discontinued.

phenytoin, calcium/magnesium/potassium/sodium oxybates.
Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

phenytoin will increase the level or effect of capivasertib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong or moderate CYP3A inducers decrease capivasertib exposure, which may reduce efficacy.

phenytoin will decrease the level or effect of capmatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin decreases levels of ceritinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.ceritinib increases levels of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Avoid or Use Alternate Drug. Avoid concurrent use of CYP2C9 substrates known to have narrow therapeutic indices or substrates primarily metabolized by CYP2C9 during treatment with ceritinib; if use of these medications is unavoidable, consider dose.

phenytoin will decrease the level or effect of cobicistat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration is necessary, monitor for lack or loss of virologic response from cobicistat

phenytoin will decrease the level or effect of copanlisib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of copanlisib with strong CYP3A4 inducers.

phenytoin decreases levels of cyclosporine by increasing metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of dabigatran by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Avoid coadministration. P-gp inducers reduce systemic exposure of dabigatran

phenytoin decreases levels of dabrafenib by increasing metabolism. Avoid or Use Alternate Drug. Strong CYP2C8 inducers may decrease dabrafenib levels.phenytoin decreases levels of dabrafenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of dantrolene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of daridorexant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of darolutamide by Other (see comment). Avoid or Use Alternate Drug. Darolutamide is a P-gp and CYP3A4 substrate. Avoid coadminstration of darolutamide with combined P-gp and strong or moderate CYP3A4 inducers.

phenytoin will decrease the level or effect of deflazacort by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of deflazacort with moderate or strong CYP3A4 inducers.

phenytoin decreases levels of deuruxolitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of deuruxolitinib with drugs that are both strong CYP3A4 inducers and moderate or strong CYP2C9 inducers.

phenytoin decreases levels of diazoxide choline by increasing metabolism. Avoid or Use Alternate Drug. Coadministration of diazoxide with dual strong CYP3A4 / moderate CYP1A2 inducers may decrease diazoxide choline systemic exposure.

phenytoin will decrease the level or effect of dihydroergotamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

phenytoin will decrease the level or effect of dihydroergotamine intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

phenytoin will decrease the level or effect of dolutegravir by increasing metabolism. Avoid or Use Alternate Drug. Avoid coadministration; insufficient data to recommend dosage adjustment

phenytoin, dopamine. Mechanism: pharmacodynamic synergism. Avoid or Use Alternate Drug. Increased risk of hypotension.

phenytoin will decrease the level or effect of dronedarone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

phenytoin will decrease the level or effect of duvelisib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration with a strong CYP3A inducer decreases duvelisib area under the curve (AUC), which may reduce duvelisib efficacy.

phenytoin will decrease the level or effect of edoxaban by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Avoid coadministration of edoxaban with potent P-gp inducers

phenytoin will decrease the level or effect of elacestrant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of eliglustat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong CYP3A inducers significantly decreases eliglustat exposure; coadministration not recommended

phenytoin will decrease the level or effect of elvitegravir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid; coadministration with CYP3A inducers may result in decreased plasma concentrations of elvitegravir and/or a concomitantly administered protease inhibitor and lead to loss of therapeutic effect and to possible resistance

phenytoin will decrease the level or effect of encorafenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of entrectinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of enzalutamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of erdafitinib by altering metabolism. Avoid or Use Alternate Drug. Avoid coadministration of strong CYP2C9 or CYP3A4 inducers with erdafitinib.

phenytoin will decrease the level or effect of ergotamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

phenytoin decreases levels of erlotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Erlotinib efficacy may be reduced when coadministered with a strong CYP3A4 inducer. Increase the erlotinib dosage (see Dosing) if coadministration cannot be avoided.

phenytoin will decrease the level or effect of erythromycin base by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

phenytoin will decrease the level or effect of erythromycin ethylsuccinate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

phenytoin will decrease the level or effect of erythromycin lactobionate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

phenytoin will decrease the level or effect of erythromycin stearate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

phenytoin will decrease the level or effect of ethinylestradiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. The efficacy of hormonal contraceptives may be reduced. Use of a nonhormonal contraceptive is recommended.

phenytoin will decrease the level or effect of etravirine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Etravirine and phenytoin should not be coadministered. Concomitant use of etravirine and phenytoin may result in decreased etravirine plasma concentrations and loss of therapeutic effect of etravirine. phenytoin will decrease the level or effect of etravirine by increasing metabolism. Avoid or Use Alternate Drug. Concomitant use of etravirine and phenytoin may result in decreased etravirine plasma concentrations and loss of therapeutic effect of etravirine. etravirine will increase the level or effect of phenytoin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Etravirine and phenytoin should not be coadministered. Concomitant use of etravirine and phenytoin may result in decreased etravirine plasma concentrations and loss of therapeutic effect of etravirine. In addition, etravirine may inhibit the CYP metabolism of phenytoin, resulting in increased phenytoin concentrations. phenytoin will decrease the level or effect of etravirine by affecting hepatic enzyme CYP2C9/10 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of everolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.phenytoin will decrease the level or effect of everolimus by P-glycoprotein (MDR1) efflux transporter. Contraindicated.

phenytoin will decrease the level or effect of fedratinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Effect of coadministering a strong CYP3A4 inducer with fedratinib has not been studied.

phenytoin will increase the level or effect of fexinidazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. CYP450 inducers may significantly increase plasma concentrations of fexinidazole?s active metabolites: fexinidazole sulfoxide (M1) and fexinidazole sulfone (M2). M2 plasma concentrations associated with increased QT prolongation risks.

phenytoin will decrease the level or effect of finerenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of fostamatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of fruquintinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of futibatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of futibatinib with drugs that are dual P-gp and strong CYP3A inducers may decrease futibatinib efficacy.

phenytoin will decrease the level or effect of ganaxolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of ganaxolone with moderate or strong CYP3A4 inducers. If coadministration unavoidable, consider increasing ganaxolone dose; however, do not exceed maximum daily dose for weight.

phenytoin will decrease the level or effect of gepirone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin decreases levels of gepotidacin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Gepotidacin is a CYP3A4 substrate. Coadministration with strong CYP3A4 inducers may decrease gepotidacin systemic exposure.

phenytoin will decrease the level or effect of gilteritinib by Other (see comment). Avoid or Use Alternate Drug. Gilteritinib is a P-gp and CYP3A4 substrates. Coadministration of gilteritinib with a combined P-gp and strong CYP3A inducer decreases gilteritinib exposure and efficacy.

phenytoin will decrease the level or effect of glasdegib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of glasdegib with strong CYP3A inducers.

phenytoin will decrease the level or effect of glecaprevir/pibrentasvir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of haloperidol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin decreases levels of ibrutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong CYP3A inducers decrease ibrutinib plasma concentrations by ~10-fold.

phenytoin will decrease the level or effect of idelalisib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration; strong CYP3A4 inducers significantly decrease idelalisib systemic exposure

phenytoin will decrease the level or effect of infigratinib (DSC) by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of irinotecan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of irinotecan liposomal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of isosorbide dinitrate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of isosorbide mononitrate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of istradefylline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of istradefylline with strong CYP3A4 inducers.

phenytoin decreases levels of itraconazole by increasing metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of ivabradine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of ivabradine with moderate CYP3A4 inducers.

phenytoin decreases levels of ivacaftor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration with strong CYP3A4 inducers; systemic exposure of ivacaftor substantially reduced (ie, ~9-fold).

phenytoin will decrease the level or effect of ivosidenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of ivosidenib with strong CYP3A4 inducers decreased ivosidenib plasma concentrations.ivosidenib will decrease the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of sensitive CYP2C9 substrates with ivosidenib or replace with alternate therapies. If coadministration is unavoidable, monitor patients for loss of therapeutic effect of these drugs.

phenytoin will decrease the level or effect of ixazomib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of ixazomib with strong CYP3A inducers. Strong inducers have been shown to decrease ixazomib Cmax by 54% and AUC by 74%.

phenytoin will decrease the level or effect of lansoprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Consider alternative for one of the interacting drugsphenytoin will decrease the level or effect of lansoprazole by affecting hepatic enzyme CYP2C19 metabolism. Avoid or Use Alternate Drug. Consider alternative for one of the interacting drugs

phenytoin will decrease the level or effect of larotrectinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration of larotrectinib with strong CYP3A4 inducers is unavoidable, double larotrectinib dose. Resume prior larotrectinib dose once CYP3A4 inducer discontinued for 3-5 half-lives

phenytoin will decrease the level or effect of lefamulin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of lefamulin with strong or moderate CYP3A inducers unless the benefit outweighs risks. Monitor for reduced efficacy.

phenytoin will decrease the level or effect of lemborexant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of leniolisib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of letermovir by Other (see comment). Avoid or Use Alternate Drug. Coadministration of letermovir with UCT1A1/3 inducers is not recommended.phenytoin will decrease the level or effect of letermovir by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Coadministration of letermovir with P-gp inducers is not recommended.

phenytoin decreases levels of lidocaine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of lomitapide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of losartan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of lovastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

phenytoin will decrease the level or effect of lumateperone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of lurbinectedin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of macimorelin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Potential for false positive test results if macimorelin and strong CYP3A4 inducers are coadministered. Discontinue strong CYP3A4 inducer, allowing for sufficient washout time, before testing.

phenytoin will decrease the level or effect of macitentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministering macitentan with strong CYP3A4 inducers

phenytoin will decrease the level or effect of mavorixafor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin decreases levels of mebendazole by increasing metabolism. Contraindicated.

phenytoin will decrease the level or effect of mefloquine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin decreases levels of mestranol by increasing metabolism. Avoid or Use Alternate Drug. May result in contraceptive failure.

phenytoin decreases levels of methadone by increasing metabolism. Contraindicated.

phenytoin, metoclopramide intranasal.
Either increases effects of the other by Other (see comment). Avoid or Use Alternate Drug.
Comment: Avoid use of metoclopramide intranasal or interacting drug, depending on importance of drug to patient.

phenytoin will decrease the level or effect of midostaurin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong CYP3A4 inducers may decrease midostaurin concentrations resulting in reduced efficacy.

phenytoin decreases levels of mitapivat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of mitapivat with strong CYP3A inducers.

phenytoin will decrease the level or effect of naldemedine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration with strong CYP3A4 inducers.

phenytoin will decrease the level or effect of neratinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of neratinib with strong/moderate CYP3A4 inducers.

phenytoin will decrease the level or effect of netupitant/palonosetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Netupitant is mainly metabolized by CYP3A4; avoid use in patients who are chronically using a strong CYP3A4 inducer

phenytoin will decrease the level or effect of nifedipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Phenytoin decreases systemic exposure of nifedipine by about 70%

phenytoin decreases levels of nintedanib by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Avoid coadministration, particularly for P-gp inducers that are also CYP3A4 inducers; nintedanib is a substrate of P-gp and to a less extent CYP3A4.

phenytoin will decrease the level or effect of nirogacestat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

nitazoxanide, phenytoin.
Either increases levels of the other by Mechanism: plasma protein binding competition. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of norethindrone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration unless benefit outweighs risk. When coadministered, hormonal contraceptives are not a reliable method of effective birth control. Concomitant use may increase incidence of menstruation associated adverse effects (amenorrhea, dysmenorrhea, menorrhagia).

phenytoin will decrease the level or effect of norethindrone acetate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration unless benefit outweighs risk. When coadministered, hormonal contraceptives are not a reliable method of effective birth control. Concomitant use may increase incidence of menstruation associated adverse effects (amenorrhea, dysmenorrhea, menorrhagia).

phenytoin will decrease the level or effect of norethindrone transdermal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration unless benefit outweighs risk. When coadministered, hormonal contraceptives are not a reliable method of effective birth control. Concomitant use may increase incidence of menstruation associated adverse effects (amenorrhea, dysmenorrhea, menorrhagia).

phenytoin will decrease the level or effect of norgestrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Contraceptive failure is possible owing to decreased serum concentration of norgestrel. Advise patients to use an alternative method of contraception or a back-up method during coadministration, and to continue back-up contraception for 28 days after discontinuing the strong CYP3A4 inducer to ensure contraceptive reliability

phenytoin will decrease the level or effect of olanzapine/samidorphan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong CYP3A4 inducers decrease levels of olanzapine and samidorphan by~50% and ~75% respectively.

phenytoin will decrease the level or effect of olaparib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of olaparib with strong CYP3A4 inducers.

phenytoin and olopatadine intranasal both increase sedation. Avoid or Use Alternate Drug. Coadministration increases risk of CNS depression, which can lead to additive impairment of psychomotor performance and cause daytime impairment.

phenytoin will decrease the level or effect of olutasidenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong or moderate CYP3A inducers decrease olutasidenib (a CYP3A4 substrate) plasma concentrations and efficacy.

phenytoin will decrease the level or effect of omaveloxolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of osimertinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid concomitant use of osimertinib with strong CYP3A inducers.

phenytoin will decrease the level or effect of ozanimod by Other (see comment). Avoid or Use Alternate Drug. Coadministration of ozanimod (a CYP2C8 substrate) with strong CYP2C8 inducers decreases the exposure of the active metabolites (CC112273 and CC1084037) of ozanimod, which may decrease the effiicacy of ozanimod. Therefore, coadministration of ozanimod with strong CYP2C8 inducers is not recommended.

phenytoin will decrease the level or effect of palbociclib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Strong CYP3A inducers decrease palbociclib plasma exposure by ~85%.

phenytoin will decrease the level or effect of palovarotene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of pemigatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of perampanel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of pexidartinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.phenytoin and pexidartinib both increase Other (see comment). Avoid or Use Alternate Drug. Pexidartinib can cause hepatotoxicity. Avoid coadministration of pexidartinib with other products know to cause hepatoxicity.

phenytoin will decrease the level or effect of pirtobrutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin decreases levels of ponatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid unless the coadministration outweighs the possible risk of ponatinib underexposure; monitor for signs of reduced efficacy.

phenytoin will decrease the level or effect of ponesimod by Other (see comment). Avoid or Use Alternate Drug. Not recommended. Based on limited data, coadministration of strong CYP3A4 and UGT1A1 inducers (eg, rifampin, phenytoin, carbamazepine) may decrease systemic exposure of ponesimod. The clinical relevance is unclear.

phenytoin will decrease the level or effect of posaconazole by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of pralsetinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If unable to avoid, double current pralsetinib dose starting on Day 7 of coadministration with strong CYP3A inducer. After inducer has been discontinued for at least 14 days, resume previous pralsetinib dose.

phenytoin will decrease the level or effect of pretomanid by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Pretomanid is a CYP3A4 substrate. Avoid coadministration of strong or moderate CYP3A4 inducers.phenytoin, pretomanid.
Either increases toxicity of the other by Other (see comment). Avoid or Use Alternate Drug.
Comment: Pretomanid regimen associated with hepatotoxicity. Avoid alcohol and hepatotoxic agents, including herbal supplements and drugs other than bedaquiline and linezolid.

phenytoin will decrease the level or effect of progesterone intravaginal gel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Use of nonhormonal contraceptives advised

phenytoin will decrease the level or effect of progesterone micronized by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Use of nonhormonal contraceptives advised

phenytoin will decrease the level or effect of progesterone, natural by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Use of nonhormonal contraceptives advised

phenytoin will decrease the level or effect of quizartinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of rabeprazole by affecting hepatic enzyme CYP2C19 metabolism. Avoid or Use Alternate Drug. Consider alternative for one of the interacting drugs

phenytoin will decrease the level or effect of ranolazine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

phenytoin will decrease the level or effect of repotrectinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.repotrectinib will decrease the level or effect of phenytoin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Repotrectinib is a CYP3A4 inducer. Avoid coadministration with CYP3A substrates where minimal concentration changes can cause reduced efficacy, unless otherwise recommended their prescribing information.

phenytoin will decrease the level or effect of ribociclib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of ribociclib with strong CYP3A inducers should be avoided.

phenytoin will decrease the level or effect of rifabutin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of rimegepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of ripretinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration with a strong CYP3A inhibitor will decrease systemic exposure to ripretinib and its active metabolite (DP-5439), which may decrease risk of adverse reactions.

phenytoin will decrease the level or effect of ritlecitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration with strong CYP3A inducers may decrease ritlecitinib AUC and peak plasma concentration, which may result in loss of or reduced efficacy.

phenytoin will decrease the level or effect of rolapitant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Long-term coadministration of strong CYP3A4 inducers with rolapitant may significantly decrease rolapitant efficacy.

phenytoin will decrease the level or effect of romidepsin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of romidepsin and phenytoin, a potent CYP3A4 inducer, as this may decrease romidepsin concentrations and efficacy.

ropeginterferon alfa 2b and phenytoin both increase Other (see comment). Avoid or Use Alternate Drug. Narcotics, hypnotics or sedatives can produce additive neuropsychiatric side effects. Avoid use and monitor patients receiving the combination for effects of excessive CNS toxicity.

phenytoin will decrease the level or effect of selpercatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of selumetinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Potent CYP3A4 inducers are expected to cause substantial decreases in sildenafil plasma levels

phenytoin will decrease the level or effect of silodosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

phenytoin will decrease the level or effect of simvastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

phenytoin will decrease the level or effect of siponimod by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of siponimod with a drug that causes moderate CYP2C9 plus a moderate or strong CYP3A4 inducer is not recommended. Coadministration with moderate or strong CYP3A4 inducers alone is not recommended for patients with CYP2C9*1/*3 and*2/*3 genotype.

phenytoin will decrease the level or effect of sirolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

phenytoin, sodium oxybate.
Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

phenytoin will decrease the level or effect of sofosbuvir by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. P-gp inducers decrease sofosbuvir levels, and therefore decrease conversion to sofosbuvir’s active metabolite (GS-331007) responsible for 90% of pharmacologic effect

phenytoin will decrease the level or effect of sofosbuvir/velpatasvir by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Sofosbuvir and velpatasvir are substrates of the drug transporter P-gp. Potent P-gp inducers may significantly decrease sofosbuvir and velpatasvir plasma concentrations, leading to potentially reduced therapeutic effect.phenytoin will decrease the level or effect of sofosbuvir/velpatasvir by affecting hepatic enzyme CYP2B6 metabolism. Avoid or Use Alternate Drug. Velpatasvir is a substrate of CYP2B6, CYP2C8, and CYP3A4. Drugs that are moderate-to-potent inducers of CYP2B6, CYP2C8, or CYP3A4 may significantly decrease velpatasvir plasma concentrations, leading to potentially reduced therapeutic effect.phenytoin will decrease the level or effect of sofosbuvir/velpatasvir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Velpatasvir is a substrate of CYP2B6, CYP2C8, and CYP3A4. Drugs that are moderate-to-potent inducers of CYP2B6, CYP2C8, or CYP3A4 may significantly decrease velpatasvir plasma concentrations, leading to potentially reduced therapeutic effect.

phenytoin will decrease the level or effect of sonidegib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of sonidegib with strong or moderate CYP3A4 inducers.

phenytoin will decrease the level or effect of sorafenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of sotagliflozin by Other (see comment). Avoid or Use Alternate Drug. Glucuronidation by UGT1A9, to form the 3-O-glucuronide, was identified as a major metabolic pathway for sotagliflozin. Coadministration of UGT1A9 inducers may decrease exposure to sotagliflozin, which may decrease efficacy.

phenytoin will decrease the level or effect of sotorasib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of sparsentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of stiripentol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If unable to avoid coadministration of stiripentol with strong CYP3A4 inducers, increase stiripentol dose.phenytoin will decrease the level or effect of stiripentol by affecting hepatic enzyme CYP2C19 metabolism. Avoid or Use Alternate Drug. If unable to avoid coadministration of stiripentol with strong CYP1A2 inducers, increase stiripentol dose.

phenytoin decreases levels of suzetrigine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of suzetrigine with strong or moderate CYP3A inducers.

phenytoin will decrease the level or effect of tamsulosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of tazemetostat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of tetracycline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of tezacaftor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of tivozanib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of tolvaptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

phenytoin will decrease the level or effect of tovorafenib by increasing metabolism. Avoid or Use Alternate Drug. Avoid coadministration of tovorafenib (a CYP2C8 substrate) with strong or moderate CYP2C8 inducers.

phenytoin will decrease the level or effect of trabectedin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of trimipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of tucatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.phenytoin will decrease the level or effect of tucatinib by Other (see comment). Avoid or Use Alternate Drug. Coadministration of tucatinib (a CYP2C8 substrate) with a strong or moderate CYP2C8 inducer decreases tucatinib plasma concentrations.

phenytoin will decrease the level or effect of ubrogepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of ulipristal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of upadacitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid upadacitinib coadministration with strong CYP3A4 inducers.

phenytoin will decrease the level or effect of valbenazine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Concomitant use not recommended.

phenytoin decreases levels of vanzacaftor/tezacaftor/deutivacaftor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of vanzacaftor/tezacaftor/deutivacaftor with strong or moderate CYP3A inducers.

phenytoin will decrease the level or effect of velpatasvir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

phenytoin decreases levels of vemurafenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of venetoclax by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of venetoclax with strong or moderate CYP3A inducers. Consider alternative treatment with agents that have less CYP3A induction.

phenytoin will decrease the level or effect of voclosporin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of vonoprazan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin decreases levels of vorapaxar by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin decreases levels of vorasidenib by affecting hepatic enzyme CYP1A2 metabolism. Avoid or Use Alternate Drug. Vorasidenib is a sensitive CYP1A2 substrate and coadministration with moderate CYP1A2 inducers may decrease vorasidenib exposure and result in reduced vorasidenib efficacy.

phenytoin will decrease the level or effect of voriconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of vortioxetine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin will decrease the level or effect of voxilaprevir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

phenytoin will decrease the level or effect of zanubrutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of zanubutinib with strong CYP3A4 inducers.

phenytoin will decrease the level or effect of zuranolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

phenytoin decreases levels of abiraterone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Avoid coadministration of abiraterone with strong CYP3A4 inducers; if a strong CYP3A4 inducer must be used, increase abiraterone dosage frequency from once daily to twice daily.

phenytoin decreases levels of albendazole by increasing metabolism. Use Caution/Monitor. Phenytoin decreases levels of albendazole active metabolites; monitor for decreased efficacy.

phenytoin will decrease the level or effect of almotriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

alpelisib will decrease the level or effect of phenytoin by pharmacodynamic synergism. Modify Therapy/Monitor Closely.

phenytoin will decrease the level or effect of alprazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of amikacin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

amiodarone will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of amiodarone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. An increased risk of phenytoin toxicity (ataxia, hyperreflexa, nystagmus, tremor) and/or decreased amiodarone concentrations. Because of the long half-life of amiodarone, the full extent of this interaction may not be evident for several weeks; careful monitoring is required.

phenytoin will decrease the level or effect of amitriptyline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor therapeutic efficacy of amitriptyline; an increased dose may be required. Serum phenytoin levels should be obtained when tricyclic antidepressant agents are added to therapy due to the potential for impaired phenytoin metabolism and decreased seizure threshold. Tricyclic antidepressants when given concomitantly with anticonvulsants can increase CNS depression.phenytoin will decrease the level or effect of amitriptyline by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Monitor therapeutic efficacy of amitriptyline; an increased dose may be required. Serum phenytoin levels should be obtained when tricyclic antidepressant agents are added to therapy due to the potential for impaired phenytoin metabolism and decreased seizure threshold. Tricyclic antidepressants when given concomitantly with anticonvulsants can increase CNS depression.

amlodipine will increase the level or effect of phenytoin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.

amobarbital will decrease the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

antithrombin alfa increases levels of phenytoin by unknown mechanism. Use Caution/Monitor.phenytoin, antithrombin alfa. Other (see comment). Use Caution/Monitor.
Comment: Hydantoin anticonvulsants increase anticoagulant effects at first, then decrease those effects with continued use (2+ wks). There are multiple mechanisms involved, including enzyme induction, plasma protein binding site competition, and additive effects on prothrombin time.

antithrombin III increases levels of phenytoin by unknown mechanism. Use Caution/Monitor.phenytoin, antithrombin III. Other (see comment). Use Caution/Monitor.
Comment: Hydantoin anticonvulsants increase anticoagulant effects at first, then decrease those effects with continued use (2+ wks). There are multiple mechanisms involved, including enzyme induction, plasma protein binding site competition, and additive effects on prothrombin time.

apalutamide will decrease the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Coadministration of apalutamide, a weak CYP2C9 inducer, with drugs that are CYP2C9 substrates can result in lower exposure to these medications. Evaluate for loss of therapeutic effect if medication must be coadministered.

phenytoin will decrease the level or effect of aprepitant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

argatroban increases levels of phenytoin by unknown mechanism. Use Caution/Monitor.phenytoin, argatroban. Other (see comment). Use Caution/Monitor.
Comment: Hydantoin anticonvulsants increase anticoagulant effects at first, then decrease those effects with continued use (2+ wks). There are multiple mechanisms involved, including enzyme induction, plasma protein binding site competition, and additive effects on prothrombin time.

phenytoin will decrease the level or effect of aripiprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of artesunate by increasing metabolism. Use Caution/Monitor. Coadministration may decrease AUC and peak plasma concentration of active artesunate metabolite (DHA) by inducing UGT. Monitor for decreased efficacy.

phenytoin will decrease the level or effect of atogepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Recommended atogepant dosage with concomitant use of strong or moderate CYP3A4 inducers is 30 mg or 60 mg qDay.

phenytoin will decrease the level or effect of atorvastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of avanafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. For patients with ED, monitor response carefully because of potential for decreased effectiveness.

phenytoin will decrease the level or effect of avatrombopag by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. When treating ITP, coadministration of avatrombopag with a moderate or strong dual CYP2C9/3A4 inducer requires an increased avatrombopag starting dose. Refer to drug monograph for specific recommendations.

phenytoin will decrease the level or effect of bazedoxifene/conjugated estrogens by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of bazedoxifene/conjugated estrogens by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. If the estrogen is being used for contraception then loss of contraception may occur. phenytoin decreases levels of bazedoxifene/conjugated estrogens by increasing metabolism. Use Caution/Monitor. A reduction in bazedoxifene exposure may be associated with an increase risk of endometrial hyperplasia.

phenytoin will decrease the level or effect of belumosudil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Increase belumosudil dosage to 200 mg PO BID when coadministered with strong CYP3A inducers.

bemiparin increases levels of phenytoin by unknown mechanism. Use Caution/Monitor.phenytoin, bemiparin. Other (see comment). Use Caution/Monitor.
Comment: Hydantoin anticonvulsants increase anticoagulant effects at first, then decrease those effects with continued use (2+ wks). There are multiple mechanisms involved, including enzyme induction, plasma protein binding site competition, and additive effects on prothrombin time.

phenytoin decreases levels of bendamustine by affecting hepatic enzyme CYP1A2 metabolism. Use Caution/Monitor. Consider alternate therapy due to risk of decreased bendamustine exposure, which may result in reduced efficacy. In vitro, bendamustine is a CYP1A2 substrate.

phenytoin will decrease the level or effect of benzhydrocodone/acetaminophen by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Caution when discontinuing CYP3A4 inducers that are coadministered with benzhydrocodone (prodrug of hydrocodone); plasma concentrations of hydrocodone may increase and can result in potentially fatal respiratory depression.

phenytoin decreases levels of berotralstat by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin will decrease the level or effect of bexagliflozin by Other (see comment). Modify Therapy/Monitor Closely. Bexagliflozin is a major substrate of UGT1A9. If coadministered with a UGT1A9 inducer, consider adding another antihyperglycemic agent in patients requiring additional glycemic control.

phenytoin will decrease the level or effect of bexarotene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

bivalirudin increases levels of phenytoin by unknown mechanism. Use Caution/Monitor.phenytoin, bivalirudin. Other (see comment). Use Caution/Monitor.
Comment: Hydantoin anticonvulsants increase anticoagulant effects at first, then decrease those effects with continued use (2+ wks). There are multiple mechanisms involved, including enzyme induction, plasma protein binding site competition, and additive effects on prothrombin time.

bleomycin decreases levels of phenytoin by increasing metabolism. Use Caution/Monitor.

blinatumomab increases levels of phenytoin by decreasing metabolism. Modify Therapy/Monitor Closely. Treatment initiation causes transient release of cytokines that may suppress CYP450 enzymes; highest drug-drug interaction risk is during the first 9 days of the first cycle and the first 2 days of the 2nd cycle in patients who are receiving concomitant CYP450 substrates, particularly those with a narrow therapeutic index.

phenytoin will decrease the level or effect of bortezomib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

bosentan will decrease the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

phenytoin decreases levels of brentuximab vedotin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

brexanolone, phenytoin.
Either increases toxicity of the other by sedation. Use Caution/Monitor.

phenytoin will decrease the level or effect of brexpiprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Double brexpiprazole dose over 1-2 weeks if administered with a strong CYP3A4 inducer.

phenytoin will decrease the level or effect of brivaracetam by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. Brivaracetam plasma concentration decreased by 21%.brivaracetam increases levels of phenytoin by decreasing metabolism. Use Caution/Monitor. Up to 20% increase in phenytoin plasma concentrations observed. Monitor phenytoin levels when brivaracetam is coadministered or discontinued from ongoing phenytoin therapy. .

brodalumab, phenytoin. Other (see comment). Use Caution/Monitor.
Comment: Formation of CYP450 enzymes can be altered by increased levels of certain cytokines during chronic inflammation; thus, brodalumab could normalize the formation of CYP450 enzymes. Upon initiation or discontinuation of brodalumab in patients who are receiving concomitant CYP450 substrates, particularly those with a narrow therapeutic index, consider monitoring for therapeutic effect.

phenytoin will decrease the level or effect of bromocriptine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of budesonide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of budesonide by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin will decrease the level or effect of buprenorphine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of buprenorphine buccal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of buprenorphine subdermal implant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Monitor patients already on buprenorphine subdermal implant who require newly-initiated treatment with CYP3A4 inducer for signs and symptoms of withdrawal. If the dose of the concomitant CYP3A4 inducer cannot be reduced or discontinued, implant removal may be necessary and the patient should then be treated with a buprenorphine dosage form that permits dose adjustments. If a CYP3A4 inducer is discontinued in a patient who has been stabilized on buprenorphine, monitor the patient for overmedication.

phenytoin will decrease the level or effect of buprenorphine transdermal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of buprenorphine, long-acting injection by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Patients who transfer to buprenorphine long-acting injection from transmucosal buprenorphine coadministered with CYP3A4 inducers should be monitored to ensure buprenorphine plasma levels are adequate. If the buprenorphine dose is inadequate and the CYP3A4 inducer cannot be reduced or discontinued, transition the patient back to a buprenorphine formulation that permits dose adjustments.

phenytoin will decrease the level or effect of buspirone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin decreases levels of busulfan by increasing hepatic clearance. Use Caution/Monitor.phenytoin will decrease the level or effect of busulfan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

butabarbital will decrease the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

butalbital will decrease the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of cabazitaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration of strong CYP3A4 inducers may decrease cabazitaxel concentrations. Avoid coadministration.

phenytoin, calcifediol. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Drugs that stimulate microsomal hydroxylation reduce the half-life of calcifediol.

phenytoin will decrease the level or effect of calcitriol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.

phenytoin decreases levels of canagliflozin by increasing metabolism. Use Caution/Monitor. Coadministration with potent UGT enzyme inducers: Consider increasing dose to 300 mg qDay if 100 mg/day tolerate and additional glycemic control required (eGFR must be >60 mL/min/1.73 m2 to increase dose); if eGFR <60 mL/min/1.73 m2, consider using a different antihyperglycemic agent.

phenytoin will decrease the level or effect of cannabidiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Consider an increase in cannabidiol dosage (based on clinical response and tolerability) when coadministered with a strong CYP3A4 inducer.cannabidiol will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Consider reducing the dose of sensitive CYP2C19 substrates, as clinically appropriate, when coadministered with cannabidiol. cannabidiol will increase the level or effect of phenytoin by decreasing metabolism. Modify Therapy/Monitor Closely. Cannabidiol may potentially inhibit CYP2C9 activity. Consider reducing the dose when concomitantly using CYP2C9 substrates.Cannabidiol may potentially inhibit CYP2C9 activity. Consider reducing the dose when concomitantly using CYP2C9 substrates.

capecitabine increases levels of phenytoin by unknown mechanism. Use Caution/Monitor. Based on case reports.

carbamazepine will decrease the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of carbamazepine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

carboplatin decreases levels of phenytoin by unknown mechanism. Use Caution/Monitor.

carmustine decreases levels of phenytoin by unknown mechanism. Use Caution/Monitor.

cenobamate will increase the level or effect of phenytoin by unspecified interaction mechanism. Modify Therapy/Monitor Closely. Concomitant use of phenytoin with multiple doses of cenobamate 200 mg qDay increased phenytoin mean Cmax and AUC by 70% and 80. Gradually decrease phenytoin dosage by up to 50% when used concomitantly with cenobamate.cenobamate will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Consider a dose reduction of CYP2C19 substrates, as clinically appropriate, when used concomitantly with cenobamate. cenobamate, phenytoin.
Either increases effects of the other by sedation. Use Caution/Monitor.

chloramphenicol increases levels of phenytoin by decreasing metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of chlordiazepoxide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.

phenytoin will decrease the level or effect of chloroquine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of cilostazol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

cimetidine will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of cinacalcet by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

ciprofloxacin decreases effects of phenytoin by unknown mechanism. Use Caution/Monitor. Ciprofloxacin has been reported to both increase and decrease phenytoin concentrations. Additional clinical evidence is needed however; phenytoin serum concentrations should be monitored in patients.

phenytoin decreases effects of cisatracurium by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. Monitor closely for more rapid recovery from neuromuscular blockade than expected; infusion rate requirements may be higher.

cisplatin decreases levels of phenytoin by unknown mechanism. Use Caution/Monitor.

phenytoin will decrease the level or effect of citalopram by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of clomipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of clonazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will increase the level or effect of clopidogrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. CYP3A4 inducers may increase the metabolism of clopidogrel to its active metabolite. Monitor patients for potential increase in antiplatelet effects when CYP3A4 inducers are used in combination with clopidogrel

phenytoin will decrease the level or effect of clorazepate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of clozapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. When adding phenytoin therapy to patients stabilized on clozapine, monitor patient closely for worsening of psychotic symptoms. If needed, increase the clozapine dose cautiously on basis of psychotic symptoms. Conversely, when phenytoin is discontinued, levels of clozapine may significantly increase.

phenytoin will decrease the level or effect of colchicine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

colesevelam will decrease the level or effect of phenytoin by Mechanism: inhibition of GI absorption. Applies only to oral form of both agents. Modify Therapy/Monitor Closely. Administer phenytoin at least 4 hr before colesevelam

phenytoin will decrease the level or effect of conivaptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of conjugated estrogens by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of conjugated estrogens by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. If the estrogen is being used for contraception then loss of contraception may occur.

phenytoin will decrease the level or effect of conjugated estrogens, vaginal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of conjugated estrogens, vaginal by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. If the estrogen is being used for contraception then loss of contraception may occur.

phenytoin will decrease the level or effect of cortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of cortisone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin decreases levels of crinecerfont by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Increase crinecerfont morning and evening doses 2-fold when coadministered with a strong CYP3A4 inducer. .

phenytoin decreases levels of crizotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Concomitant use of strong CYP3A inducers should be avoided. .crizotinib increases levels of phenytoin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration of crizotinib with CYP3A substrates with narrow therapeutic indices should be avoided.

phenytoin will decrease the level or effect of cyclosporine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of cyclosporine by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

dalteparin increases levels of phenytoin by unknown mechanism. Use Caution/Monitor.phenytoin, dalteparin. Other (see comment). Use Caution/Monitor.
Comment: Hydantoin anticonvulsants increase anticoagulant effects at first, then decrease those effects with continued use (2+ wks). There are multiple mechanisms involved, including enzyme induction, plasma protein binding site competition, and additive effects on prothrombin time.

phenytoin increases toxicity of dapsone topical by altering metabolism. Modify Therapy/Monitor Closely. May induce methemoglobinemia.

phenytoin and daridorexant both increase sedation. Modify Therapy/Monitor Closely. Coadministration increases risk of CNS depression, which can lead to additive impairment of psychomotor performance and cause daytime impairment.

phenytoin will decrease the level or effect of darifenacin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of dasatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Concomitant use will lead to decreased dasatinib plasma concentrations. Consider using alternative therapeutic agents with low enzyme induction potential for coadministration with dasatinib. However, if concomitant use with phenytoin is required, consider increasing the dasatinib dose and monitor the patient closely for dasatinib toxicity (myelosuppression, fluid retention, diarrhea, hemorrhage, or skin rash).

phenytoin decreases levels of deferasirox by Other (see comment). Use Caution/Monitor.
Comment: Avoid concomitant use of potent UGT inducers with deferasirox. If co-administration is required then consider increasing initial dose of deferasirox to 30 mg/kg and monitor ferritin levels and clinical response.

phenytoin will decrease the level or effect of deflazacort by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin and deutetrabenazine both increase sedation. Use Caution/Monitor.

phenytoin will decrease the level or effect of dexamethasone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of dexamethasone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin will decrease the level or effect of dexlansoprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of diazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of diazepam buccal by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. Strong or moderate CYP2C19 inducers may increase rate of diazepam elimination; therefore, efficacy of diazepam may be decreased.phenytoin will decrease the level or effect of diazepam buccal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Strong or moderate CYP3A4 inducers may increase rate of diazepam elimination; therefore, efficacy of diazepam may be decreased.

phenytoin will decrease the level or effect of diazepam intranasal by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. Strong or moderate CYP2C19 inducers may increase rate of diazepam elimination; therefore, efficacy of diazepam may be decreased.phenytoin will decrease the level or effect of diazepam intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Strong or moderate CYP3A4 inducers may increase rate of diazepam elimination; therefore, efficacy of diazepam may be decreased.

difelikefalin and phenytoin both increase sedation. Use Caution/Monitor.

phenytoin will decrease the level or effect of digoxin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin will decrease the level or effect of diltiazem by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of disopyramide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Phenytoin decreases the levels of disopyramide but can also increase the toxicity.phenytoin increases toxicity of disopyramide by increasing metabolism. Use Caution/Monitor. Hydantoins decreases the level, but increases the toxicity, of disopyramide.

disulfiram will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of docetaxel by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.docetaxel decreases levels of phenytoin by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.docetaxel decreases levels of phenytoin by increasing metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of doxorubicin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.doxorubicin decreases levels of phenytoin by increasing metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of doxorubicin liposomal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.doxorubicin liposomal decreases levels of phenytoin by increasing metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of dronabinol by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Dronabinol is a CYP2C9 substrate.phenytoin will decrease the level or effect of dronabinol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Dronabinol is a CYP3A4 substrate.dronabinol increases levels of phenytoin by plasma protein binding competition. Modify Therapy/Monitor Closely. Dronabinol is highly bound to plasma proteins and may displace and increase the free fraction of other concomitantly administered highly protein-bound drugs. This has not been confirmed in vivo. Caution with narrow therapeutic index drugs that are highly protein bound when initiating or increasing the dose of dronabinol.

dulaglutide, phenytoin. Other (see comment). Use Caution/Monitor.
Comment: Dulaglutide slows gastric emptying and may impact absorption of concomitantly administered oral medications; be particularly cautious when coadministered with drugs that have a narrow therapeutic index.

dupilumab, phenytoin. Other (see comment). Use Caution/Monitor.
Comment: Formation of CYP450 enzymes can be altered by increased levels of certain cytokines during chronic inflammation; thus, dupilumab could normalize the formation of CYP450 enzymes. Upon initiation or discontinuation of dupilumab in patients who are receiving concomitant CYP450 substrates, particularly those with a narrow therapeutic index, consider monitoring for therapeutic effect.

phenytoin will decrease the level or effect of duvelisib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

efavirenz will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of efavirenz by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. When given together, periodic monitoring for reduced efavirenz efficacy and phenytoin plasma concentrations are recommended .phenytoin will increase the level or effect of efavirenz by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

elagolix will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Elagolix is a weak CYP2C19 inhibitor. Caution with sensitive CYP2C19 substrates.phenytoin will decrease the level or effect of elagolix by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of eletriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

eliglustat increases levels of phenytoin by P-glycoprotein (MDR1) efflux transporter. Modify Therapy/Monitor Closely. Monitor therapeutic drug concentrations, as indicated, or consider reducing the dosage of the P-gp substrate and titrate to clinical effect.

elranatamab will increase the level or effect of phenytoin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Elranatamab causes cytokine release syndrome (CRS) that may suppress activity of CYP enzymes, resulting in increased exposure of CYP substrates. This is more likely to occur from initiation of elranatamab step-up dosing up to 14 days after the first treatment dose and during and after CRS.

elvitegravir/cobicistat/emtricitabine/tenofovir DF decreases levels of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Elvitegravir is a moderate CYP2C9 inducer.

enasidenib will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. Enasidenib (a weak CYP2C19 inhibitor) may increase systemic exposure of sensitive CYP2C19 substrates. Monitor and adjust dose of substrate as clinically indicated.enasidenib will decrease the level or effect of phenytoin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Enasidenib (a weak CYP3A4 inducer) may decrease systemic exposure of CYP3A4 substrates. Monitor and adjust dose of substrate as clinically indicated.

phenytoin will decrease the level or effect of enfortumab vedotin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

enoxaparin increases levels of phenytoin by unknown mechanism. Use Caution/Monitor.phenytoin, enoxaparin. Other (see comment). Use Caution/Monitor.
Comment: Hydantoin anticonvulsants increase anticoagulant effects at first, then decrease those effects with continued use (2+ wks). There are multiple mechanisms involved, including enzyme induction, plasma protein binding site competition, and additive effects on prothrombin time.

epcoritamab, phenytoin. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Epcoritamab causes release of cytokines that may suppress activity of CYP enzymes, resulting in increased exposure of CYP substrates. For certain CYP substrates, minimal changes in their concentration may lead to serious adverse reactions. If needed, modify therapy as recommended in the substrate’s prescribing information. .

phenytoin decreases levels of eravacycline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Increase eravacycline dose (see Adult Dosing) if coadministered with a strong CYP3A4 inducer. No dosage adjustment is warranted with weak or moderate CYP3A4 inducers. .

phenytoin will decrease the level or effect of escitalopram by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

esketamine intranasal, phenytoin.
Either increases toxicity of the other by sedation. Modify Therapy/Monitor Closely.

phenytoin will decrease the level or effect of eslicarbazepine acetate by increasing metabolism. Use Caution/Monitor. Higher dosage of eslicarbazepine may be necessary and dose adjustment may be needed for phenytoineslicarbazepine acetate will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.

esomeprazole will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of esomeprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of estradiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of estradiol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin will decrease the level or effect of estradiol vaginal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of estrogens conjugated synthetic by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of estrogens conjugated synthetic by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. If the estrogen is being used for contraception then loss of contraception may occur.

phenytoin will decrease the level or effect of estrogens esterified by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. If the estrogen is being used for contraception then loss of contraception may occur.

phenytoin will decrease the level or effect of estropipate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of estropipate by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. If the estrogen is being used for contraception then loss of contraception may occur.

phenytoin will decrease the level or effect of eszopiclone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

ethanol decreases levels of phenytoin by increasing metabolism. Use Caution/Monitor. Decreased phenytoin levels may be seen with chronic alcohol ingestion.ethanol increases levels of phenytoin by decreasing metabolism. Use Caution/Monitor. Increased phenytoin levels may be seen with acute alcohol ingestion.

phenytoin, ethosuximide. Other (see comment). Use Caution/Monitor.
Comment: Ethosuximide may enhance CNS depressant effects and may increase serum concentrations of phenytoin. Phenytoin, a CYP3A4 inducer, may decrease plasma levels of ethosuximide (a CYP3A4 substrate.).

phenytoin will decrease the level or effect of etonogestrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of etoposide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of exemestane by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. For patients receiving exemestane with a potent CYP3A4 inducer the recommended dose of exemestane is 50 mg daily after a meal.

felbamate will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of felbamate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Felbamate may increase serum concentrations of phenytoin. Phenytoin, a CYP3A4 inducer, may decrease plasma levels of felbamate (a CYP3A4 substrate).

phenytoin will decrease the level or effect of felodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. When possible, avoid coadministration of these drugs and consider alternative therapy. When an alternative therapy is not possible, patients should be monitored for the desired cardiovascular effects such as heart rate, chest pain, or blood pressure.phenytoin decreases levels of felodipine by increasing metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of fentanyl by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration of fentanyl with CYP3A4 inducers could lead to a decrease in fentanyl plasma concentrations, lack of efficacy or, possibly, development of a withdrawal syndrome in a patient who has developed physical dependence to fentanyl. After stopping a CYP3A4 inducer, as the effects of the inducer decline, the fentanyl plasma concentration will increase which could increase or prolong both the therapeutic and adverse effects.

phenytoin will decrease the level or effect of fentanyl intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration of fentanyl with CYP3A4 inducers could lead to a decrease in fentanyl plasma concentrations, lack of efficacy or, possibly, development of a withdrawal syndrome in a patient who has developed physical dependence to fentanyl. After stopping a CYP3A4 inducer, as the effects of the inducer decline, the fentanyl plasma concentration will increase which could increase or prolong both the therapeutic and adverse effects.

phenytoin will decrease the level or effect of fentanyl transdermal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration of fentanyl with CYP3A4 inducers could lead to a decrease in fentanyl plasma concentrations, lack of efficacy or, possibly, development of a withdrawal syndrome in a patient who has developed physical dependence to fentanyl. After stopping a CYP3A4 inducer, as the effects of the inducer decline, the fentanyl plasma concentration will increase which could increase or prolong both the therapeutic and adverse effects.

phenytoin will decrease the level or effect of fentanyl transmucosal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration of fentanyl with CYP3A4 inducers could lead to a decrease in fentanyl plasma concentrations, lack of efficacy or, possibly, development of a withdrawal syndrome in a patient who has developed physical dependence to fentanyl. After stopping a CYP3A4 inducer, as the effects of the inducer decline, the fentanyl plasma concentration will increase which could increase or prolong both the therapeutic and adverse effects.

ferric maltol, phenytoin.
Either increases levels of the other by unspecified interaction mechanism. Modify Therapy/Monitor Closely. Coadministration of ferric maltol with certain oral medications may decrease the bioavailability of either ferric maltol and some oral drugs. For oral drugs where reductions in bioavailability may cause clinically significant effects on its safety or efficacy, separate administration of ferric maltol from these drugs. Duration of separation may depend on the absorption of the medication concomitantly administered (eg, time to peak concentration, whether the drug is an immediate or extended release product).

phenytoin will decrease the level or effect of fesoterodine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

fexinidazole will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.

fleroxacin decreases effects of phenytoin by unknown mechanism. Use Caution/Monitor. There are also case reports of quinolones increasing phenytoin levels.

phenytoin will decrease the level or effect of flibanserin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Strong CYP3A4 inducers substantially decrease flibanserin systemic exposure.

floxuridine increases levels of phenytoin by unknown mechanism. Use Caution/Monitor. Based on case reports.

fluconazole will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of fludrocortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of fludrocortisone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

fluorouracil increases levels of phenytoin by unknown mechanism. Use Caution/Monitor. Based on case reports.

fluoxetine will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of flurazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of fluticasone furoate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of fluticasone inhaled by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

fluvastatin increases levels of phenytoin by decreasing metabolism. Use Caution/Monitor.

fluvoxamine will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

fondaparinux increases levels of phenytoin by unknown mechanism. Use Caution/Monitor.phenytoin, fondaparinux. Other (see comment). Use Caution/Monitor.
Comment: Hydantoin anticonvulsants increase anticoagulant effects at first, then decrease those effects with continued use (2+ wks). There are multiple mechanisms involved, including enzyme induction, plasma protein binding site competition, and additive effects on prothrombin time.

phenytoin, fosamprenavir. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration of phenytoin and fosamprenavir alone may decrease the concentration of amprenavir, the active metabolite; when given with the combination of fosamprenavir and ritonavir an increased concentration of amprenavir is observed.

phenytoin will decrease the level or effect of fosaprepitant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin decreases effects of foscarbidopa/foslevodopa by unknown mechanism. Use Caution/Monitor.

phenytoin will decrease the level or effect of gefitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Increase gefitinib to 500 mg daily if coadministered with a strong CYP3A4 inducer. Resume gefitinib dose at 250 mg/day 7 days after discontinuing the strong inducer.

gemifloxacin decreases effects of phenytoin by unknown mechanism. Use Caution/Monitor. There are also case reports of quinolones increasing phenytoin levels.

phenytoin will decrease the level or effect of gentamicin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

givinostat will increase the level or effect of phenytoin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Givinostat is a weak CYP3A4 inhibitor. Closely monitor if coadministered with orally administered CYP3A4 sensitive substrates for which a small change in substrate plasma concentration may lead to serious toxicities.

glofitamab, phenytoin. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Glofitamab causes release of cytokines that may suppress activity of CYP enzymes, resulting in increased exposure of CYP substrates. For certain CYP substrates, minimal changes in their concentration may lead to serious adverse reactions. If needed, modify therapy as recommended in the substrate’s prescribing information. .

phenytoin decreases levels of glyburide by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Strong CYP2C9 inducers may increase glyburide metabolism.

phenytoin decreases levels of green tea by increasing metabolism. Use Caution/Monitor. (Caffeine). Potential for decreased effects of caffeine in green tea. .

phenytoin will decrease the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inducers significantly reduce guanfacine plasma concentrations and elimination half-life. If coadministered, more frequent dosing of the IR product may be required to achieve or maintain the desired hypotensive response. For patients with ADHD, FDA-approved labeling for ER guanfacine recommends that, if coadministered, doubling the recommended dose of guanfacine should be considered.

guselkumab, phenytoin. Other (see comment). Use Caution/Monitor.
Comment: Formation of CYP450 enzymes can be altered by increased levels of certain cytokines during chronic inflammation; thus, normalizing the formation of CYP450 enzymes. Upon initiation or discontinuation of guselkumab in patients who are receiving concomitant CYP450 substrates, particularly those with a narrow therapeutic index, consider monitoring for therapeutic effect.

hawthorn increases effects of phenytoin by pharmacodynamic synergism. Use Caution/Monitor.

heparin increases levels of phenytoin by unknown mechanism. Use Caution/Monitor.phenytoin, heparin. Other (see comment). Use Caution/Monitor.
Comment: Hydantoin anticonvulsants increase anticoagulant effects at first, then decrease those effects with continued use (2+ wks). There are multiple mechanisms involved, including enzyme induction, plasma protein binding site competition, and additive effects on prothrombin time.

hyaluronidase, phenytoin. Other (see comment). Use Caution/Monitor.
Comment: Drug combination has been found to be incompatible.

phenytoin will decrease the level or effect of hydrocodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Caution when discontinuing CYP3A4 inducers that are coadministered with hydrocodone; plasma concentrations of hydrocodone may increase and can result in potentially fatal respiratory depression.

phenytoin will decrease the level or effect of hydrocortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of hydrocortisone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin will decrease the level or effect of hydroxyprogesterone caproate (DSC) by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin increases effects of ifosfamide by affecting hepatic enzyme CYP2B6 metabolism. Use Caution/Monitor. Coadministration of ifosfamide with CYP2B6 inducers may increase metabolism of ifosfamide to its metabolite. Monitor for increased effects/toxicities if combined with CYP2B6 inducers.phenytoin increases toxicity of ifosfamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. CYP3A4 inducers may increase the metabolism of ifosfamide to its active alkylating metabolites. CYP3A4 inducers may increase the formation of the neurotoxic/nephrotoxic ifosfamide metabolite, chloroacetaldehyde. Closely monitor patients taking ifosfamide with CYP3A4 inducers for toxicities and consider dose adjustment.

phenytoin will decrease the level or effect of iloperidone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

imatinib will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of imatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Alternatives to phenytoin, with less enzyme induction potential, should be considered. Combo may decrease imatinib levels and efficacy. phenytoin will decrease the level or effect of imatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin will decrease the level or effect of imipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Consider phenytoin serum levels if a tricyclic antidepressant is added to therapy or if the patient begins to exhibit signs of toxicity; lower doses of phenytoin may be required. If phenytoin is added to tricyclic antidepressant therapy, monitor for clinical efficacy of the tricyclic agent. Tricyclic antidepressants when given concomitantly with anticonvulsants can increase CNS depression.

phenytoin will decrease the level or effect of iptacopan by increasing metabolism. Use Caution/Monitor. CYP2C8 inducers may reduce efficacy of iptacopan (a CYP2C8 substrate).

phenytoin will decrease the level or effect of itraconazole by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Antifungal failure may occur due to clinically significant decreases in itraconazole serum concentrations when given with phenytoin. Increased itraconazole dosage may be needed.

phenytoin will decrease the level or effect of ivermectin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin will decrease the level or effect of ixabepilone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

ixekizumab, phenytoin. Other (see comment). Use Caution/Monitor.
Comment: Formation of CYP450 enzymes can be altered by increased levels of certain cytokines during chronic inflammation; thus, ixekizumab could normalize the formation of CYP450 enzymes. Upon initiation or discontinuation of ixekizumab in patients who are receiving concomitant CYP450 substrates, particularly those with a narrow therapeutic index, consider monitoring for therapeutic effect.

ketoconazole will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

L-methylfolate decreases levels of phenytoin by unspecified interaction mechanism. Use Caution/Monitor.

phenytoin increases toxicity of lacosamide by Other (see comment). Use Caution/Monitor.
Comment: Coadministration of lacosamide with sodium channel-blocking antiseizure drugs may increase the risk for AV block, bradycardia, or ventricular tachyarrhythmias. Monitor ECG before beginning lacosamide and after lacosamide is titrated to steady-state.

phenytoin decreases levels of lamotrigine by increasing metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. A reduction in therapeutic effectiveness of lapatinib may occur. Concomitant use of phenytoin with dasatinib, nilotinib, lapatinib, or pazopanib should be avoided.

lasmiditan, phenytoin.
Either increases effects of the other by sedation. Use Caution/Monitor. Coadministration of lasmiditan and other CNS depressant drugs, including alcohol have not been evaluated in clinical studies. Lasmiditan may cause sedation, as well as other cognitive and/or neuropsychiatric adverse reactions.

leflunomide will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

lemborexant, phenytoin.
Either increases effects of the other by sedation. Modify Therapy/Monitor Closely. Dosage adjustment may be necessary if lemborexant is coadministered with other CNS depressants because of potentially additive effects.

phenytoin will decrease the level or effect of lesinurad (DSC) by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

letermovir will decrease the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Monitor phenytoin levels.

phenytoin will decrease the level or effect of levamlodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. No information is available on the quantitative effects of CYP3A4 inducers on amlodipine. Closely monitor blood pressure when amlodipine is coadministered with CYP3A4 inducers.

phenytoin decreases effects of levodopa by unknown mechanism. Use Caution/Monitor.

levofloxacin decreases effects of phenytoin by unknown mechanism. Use Caution/Monitor. There are also case reports of quinolones increasing phenytoin levels.

levoketoconazole will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

phenytoin decreases levels of levonorgestrel intrauterine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin decreases levels of levonorgestrel oral by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of levonorgestrel oral/ethinylestradiol/ferrous bisglycinate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. The efficacy of hormonal contraceptives may be reduced. Use an alternative method of contraception or a backup method when enzyme inducers are used with combined hormonal contraceptives (CHCs), and continue backup contraception for 28 days after discontinuing enzyme inducer to ensure contraceptive reliability.

phenytoin will decrease the level or effect of linagliptin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Use of alternative treatments is strongly recommended when linagliptin is to be administered with a CYP3A4 inducer.

phenytoin will decrease the level or effect of lomustine by increasing metabolism. Use Caution/Monitor. Coadministration of enzyme inducing antiepileptics with lomustine may cause a decrease in plasma concentration and reduced efficacy of lomustine.lomustine will increase the level or effect of phenytoin by decreasing metabolism. Use Caution/Monitor. Coadministration of lomustine with phenytoin may decrease of phenytoin levels and seizure control.

lonapegsomatropin will decrease the level or effect of phenytoin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Limited published data indicate that growth hormone treatment increases cytochrome P450 (CYP450)-mediated antipyrine clearance. Caution with sensitive CYP substrates

phenytoin will decrease the level or effect of loperamide by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin will decrease the level or effect of lopinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of loratadine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

lumacaftor/ivacaftor, phenytoin. affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. In vitro studies suggest that lumacaftor may induce and ivacaftor may inhibit CYP2C19 substrates. .lumacaftor/ivacaftor, phenytoin. affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. In vitro studies suggest that lumacaftor may induce and ivacaftor may inhibit CYP2C9 substrates. .

lurasidone, phenytoin.
Either increases toxicity of the other by Other (see comment). Use Caution/Monitor.
Comment: Potential for increased CNS depressant effects when used concurrently; monitor for increased adverse effects and toxicity.

phenytoin will decrease the level or effect of maraviroc by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of maraviroc by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. The plasma concentrations and pharmacologic effects of maraviroc may be increased by phenytoin. Maraviroc dosage adjustment is recommended during concomitant therapy with phenytoin. Coadministration of maraviroc and phenytoin is contraindicated in patients with severe renal impairment.

phenytoin will decrease the level or effect of marijuana by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of medroxyprogesterone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Contraceptirve failure possible

phenytoin will decrease the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of mestranol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.mestranol decreases effects of phenytoin by decreasing metabolism. Use Caution/Monitor.

phenytoin decreases effects of metformin by pharmacodynamic antagonism. Use Caution/Monitor. Patient should be closely observed for loss of blood glucose control; when drugs are withdrawn from a patient receiving metformin, patient should be observed closely for hypoglycemia.

phenytoin will decrease the level or effect of methadone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin increases toxicity of methotrexate by Other (see comment). Use Caution/Monitor.
Comment: Methotrexate is partially bound to serum albumin, and toxicity may be increased because of displacement by certain drugs, such as phenytoin.

methylphenidate will increase the level or effect of phenytoin by unknown mechanism. Use Caution/Monitor. Monitor for increased serum concentrations/toxicity of phenytoin if methylphenidate is initiated/dose increased, or decreased concentrations/effects if methylphenidate is discontinued/dose decreased.

methylphenidate transdermal will increase the level or effect of phenytoin by decreasing metabolism. Modify Therapy/Monitor Closely. Consider decreasing the dose of these drugs when given coadministered with methylphenidate. Monitor for drug toxiticities when initiating or discontinuing methylphenidate.

phenytoin will decrease the level or effect of methylprednisolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of methylprednisolone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

metronidazole will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

phenytoin decreases levels of metyrapone by increasing metabolism. Use Caution/Monitor.

phenytoin decreases levels of mexiletine by increasing metabolism. Use Caution/Monitor.

miconazole vaginal will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of midazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

midazolam intranasal, phenytoin.
Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Concomitant use of barbiturates, alcohol, or other CNS depressants may increase the risk of hypoventilation, airway obstruction, desaturation, or apnea and may contribute to profound and/or prolonged drug effect.

phenytoin will decrease the level or effect of mifepristone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. CYP3A4 inducers have not been studied, coadministration not recommended by manufacturer

mipomersen, phenytoin.
Either increases toxicity of the other by Other (see comment). Use Caution/Monitor.
Comment: Both drugs have potential to increase hepatic enzymes; monitor LFTs.

phenytoin will decrease the level or effect of mirtazapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

mitapivat decreases levels of phenytoin by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. Monitor patients for loss of therapeutic effect if taking sensitive CYP2C19 substrates. .mitapivat decreases levels of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Monitor patients for loss of therapeutic effect if taking sensitive CYP2C9/10 substrates.mitapivat decreases levels of phenytoin by increasing metabolism. Use Caution/Monitor. Mitapivat induces UGT1A1 in vitro and may decrease systemic concentrations of UGT1A1 substrates.

mitoxantrone decreases levels of phenytoin by increasing metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of modafinil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

moxifloxacin decreases effects of phenytoin by unknown mechanism. Use Caution/Monitor. There are also case reports of quinolones increasing phenytoin levels.

nateglinide will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of nateglinide by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Inducers of CYP2C9 decrease levels of nateglinide by increasing its metabolism. Coadministration may reduce nateglinide’s hypoglycemic action.

phenytoin will decrease the level or effect of nefazodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of nelfinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of nelfinavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin will decrease the level or effect of neomycin PO by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin will decrease the level or effect of nevirapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of nicardipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

nilotinib will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Avoid concomitant use of phenytoin with nilotinib.phenytoin will decrease the level or effect of nilotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of nilotinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. A reduction in therapeutic effectiveness of nilotinib may occur. Concomitant use of phenytoin with lapatinib, nilotinib, lapatinib, or pazopanib should be avoided.

nilutamide will increase the level or effect of phenytoin by decreasing metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of nisoldipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

nitisinone will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Nitisinone inhibits CYP2C9. Caution if CYP2C9 substrate coadministered, particularly those with a narrow therapeutic index.

ofloxacin decreases effects of phenytoin by unknown mechanism. Use Caution/Monitor. There are also case reports of quinolones increasing phenytoin levels.

phenytoin will decrease the level or effect of oliceridine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. If coadministration with a CYP3A4 inducer is necessary, consider increasing oliceridine dose until stable drug effects are achieved; monitor for signs of opioid withdrawal. If inducer is discontinued, consider oliceridine dosage reduction and monitor for signs of respiratory depression.

phenytoin will decrease the level or effect of omeprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of ondansetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. No dosage adjustment for ondansetron is recommended for patients on these drugs.

oritavancin will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Oritavancin is a weak CYP2C9 inhibitor; caution if coadministered with CYP2C9 substrates that have a narrow therapeutic index

orlistat decreases levels of phenytoin by inhibition of GI absorption. Applies only to oral form of both agents. Modify Therapy/Monitor Closely. Risk of convulsions.

phenytoin will decrease the level or effect of osilodrostat by Other (see comment). Modify Therapy/Monitor Closely. Osilodrostat is a CYP3A4 and CYP2B6 subtrate. Monitor cortisol concentration and patient?s signs and symptoms during coadministration and discontinuation with strong CYP3A4 and/or CYP2B6 inducers. Adjust dose of osilodrostat if necessary.

phenytoin decreases levels of ospemifene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin decreases levels of ospemifene by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.phenytoin decreases levels of ospemifene by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.phenytoin, ospemifene.
Either increases levels of the other by plasma protein binding competition. Modify Therapy/Monitor Closely.

oxaliplatin decreases levels of phenytoin by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.oxaliplatin decreases levels of phenytoin by increasing metabolism. Use Caution/Monitor.oxaliplatin will decrease the level or effect of phenytoin by unknown mechanism. Use Caution/Monitor. Monitor phenytoin concentrations/effects during treatment with oxaliplatin. Adjust phenytoin/fosphenytoin dose as necessary to maintain concentrations in the desired range.

oxcarbazepine increases levels of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Oxcarbazepine increases levels of phenytoin at doses >1200 mg/day; monitor phenytoin levels during oxcarbazepine titration period and dosage modification; may require a decrease in phenytoin dose.

phenytoin decreases levels of oxycodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

paclitaxel decreases levels of phenytoin by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.paclitaxel decreases levels of phenytoin by increasing metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of paclitaxel by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.phenytoin will decrease the level or effect of paclitaxel by Other (see comment). Use Caution/Monitor. Paclitaxel levels/efficacy may decrease when coadministered with CYP2C8 inducers

paclitaxel protein bound decreases levels of phenytoin by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.paclitaxel protein bound decreases levels of phenytoin by increasing metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of paclitaxel protein bound by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.phenytoin will decrease the level or effect of paclitaxel protein bound by Other (see comment). Use Caution/Monitor. Paclitaxel levels/efficacy may decrease when coadministered with CYP2C8 inducers

phenytoin will decrease the level or effect of paliperidone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin decreases effects of pancuronium by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. Monitor closely for more rapid recovery from neuromuscular blockade than expected; infusion rate requirements may be higher.

phenytoin will decrease the level or effect of pantoprazole by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of paricalcitol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of paromomycin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin will decrease the level or effect of pazopanib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

peginterferon alfa 2b decreases levels of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. When patients are administered peginterferon alpha-2b with CYP2C9 substrates, the therapeutic effect of these drugs may be altered. .

pentobarbital will decrease the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

phenindione increases levels of phenytoin by unknown mechanism. Use Caution/Monitor.phenytoin, phenindione. Other (see comment). Use Caution/Monitor.
Comment: Hydantoin anticonvulsants increase anticoagulant effects at first, then decrease those effects with continued use (2+ wks). There are multiple mechanisms involved, including enzyme induction, plasma protein binding site competition, and additive effects on prothrombin time.

phenobarbital will decrease the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of pimavanserin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Avoid coadministration if possible. Monitor for reduced pimavanserin efficacy. An increase in pimavanserin dosage may be needed.

phenytoin will decrease the level or effect of pitolisant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Pitolisant exposure is decreased by 50% if coadministered with strong CYP3A4 inducers. For patients stable on pitolisant 8.9 mg/day or 17.8 mg/day, double the pitolisant dose (ie, 17.8 mg or 35.6 mg, respectively) over 7 days. If the strong CYP3A4 inducer is discontinued, reduce pitolisant dosage by half.

phenytoin will decrease the level or effect of polatuzumab vedotin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Polatuzumab undergoes catabolism to small peptides, amino acids, monomethyl auristatin E (MMAE), and unconjugated MMAE-related catabolites. MMAE is a CYP3A4 substrate. Coadministration of polatuzumab vedotin with a strong CYP3A4 inducer may decrease unconjugated MMAE AUC.

phenytoin decreases levels of posaconazole by increasing metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of prednisolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of prednisolone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin will decrease the level or effect of prednisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of prednisone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

primidone will decrease the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.phenytoin increases effects of primidone by increasing metabolism. Use Caution/Monitor. Phenytoin enhances the conversion of primidone to phenobarbital.

protamine increases levels of phenytoin by unknown mechanism. Use Caution/Monitor.phenytoin, protamine. Other (see comment). Use Caution/Monitor.
Comment: Hydantoin anticonvulsants increase anticoagulant effects at first, then decrease those effects with continued use (2+ wks). There are multiple mechanisms involved, including enzyme induction, plasma protein binding site competition, and additive effects on prothrombin time.

phenytoin will decrease the level or effect of quazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of quetiapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Increased doses of quetiapine may be required to maintain control of psychotic symptoms in patients receiving quetiapine and phenytoin. Caution should be taken if phenytoin is withdrawn from therapy or replaced with a non-inducing anticonvulsant.

phenytoin will decrease the level or effect of quinidine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin decreases levels of quinidine by increasing metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of quinine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Use caution when prescribing phenytoin and quinine together due to a decrease in quinine plasma concentrations and potential lack of efficacy.

phenytoin will decrease the level or effect of repaglinide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

rifampin will decrease the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

rifapentine will decrease the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of riociguat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Data not available for dose adjustment

phenytoin will decrease the level or effect of risperidone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

ritlecitinib will increase the level or effect of phenytoin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Ritlecitinib inhibits CYP3A4 substrates; coadministration increases AUC and peak plasma concentration sensitive substrates, which may increase risk of adverse reactions. Additional monitoring and dosage adjustment may be needed in accordance with product labeling of CYP3A substrates.

phenytoin will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin decreases levels of rivaroxaban by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Avoid concomitant use of rivaroxaban with drugs that are combined P-gp and strong CYP3A4 inducers. Consider increasing the rivaroxaban dose if these drugs must be coadministered.

phenytoin decreases effects of rocuronium by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. Monitor closely for more rapid recovery from neuromuscular blockade than expected; infusion rate requirements may be higher.

rufinamide increases levels of phenytoin by decreasing renal clearance. Use Caution/Monitor.phenytoin decreases levels of rufinamide by increasing metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of ruxolitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of ruxolitinib topical by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

sarilumab, phenytoin. Other (see comment). Use Caution/Monitor.
Comment: Formation of CYP450 enzymes can be altered by increased levels of cytokines such as IL-6. Elevated IL-6 concentration may down-regulate CYP activity, such as in patients with RA, and, hence, increase drug levels compared with subjects without RA. Blockade of IL-6 signaling by IL-6 antagonists (eg, sarilumab) might reverse the inhibitory effect of IL-6 and restore CYP activity, leading to decreased drug concentrations. Caution when initiating or discontinuing sarilumab if coadministered with CYP450 substrates, especially those with a narrow therapeutic index.

secukinumab, phenytoin. Other (see comment). Use Caution/Monitor.
Comment: Formation of CYP450 enzymes can be altered by increased levels of certain cytokines during chronic inflammation; thus, secukinumab could normalize the formation of CYP450 enzymes. Upon initiation or discontinuation of secukinumab in patients who are receiving concomitant CYP450 substrates, particularly those with a narrow therapeutic index, consider monitoring for therapeutic effect.

phenytoin will decrease the level or effect of selexipag by increasing metabolism. Modify Therapy/Monitor Closely. Increase selexipag dose (up to 2-fold) if coadministered with strong CYP2C8 inducers.

sertraline increases levels of phenytoin by decreasing metabolism. Use Caution/Monitor.

sevelamer decreases levels of phenytoin by increasing elimination. Use Caution/Monitor.

phenytoin will decrease the level or effect of silodosin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin will decrease the level or effect of sirolimus by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

sodium sulfate/?magnesium sulfate/potassium chloride increases toxicity of phenytoin by Other (see comment). Use Caution/Monitor.
Comment: Coadministration with medications that cause fluid and electrolyte abnormalities may increase the risk of adverse events of seizure, arrhythmias, and renal impairment.

sodium sulfate/potassium sulfate/magnesium sulfate increases toxicity of phenytoin by Other (see comment). Use Caution/Monitor.
Comment: Coadministration with medications that cause fluid and electrolyte abnormalities may increase the risk of adverse events of seizure, arrhythmias, and renal impairment.

phenytoin will decrease the level or effect of solifenacin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

somapacitan will decrease the level or effect of phenytoin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Limited published data indicate that growth hormone treatment increases cytochrome P450 (CYP450)-mediated antipyrine clearance. Caution with sensitive CYP substrates

somatrogon will decrease the level or effect of phenytoin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Limited published data indicate that growth hormone treatment increases cytochrome P450 (CYP450)-mediated antipyrine clearance. Caution with sensitive CYP substrates

somatropin will decrease the level or effect of phenytoin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Limited published data indicate that growth hormone treatment increases cytochrome P450 (CYP450)-mediated antipyrine clearance. Caution with sensitive CYP substrates

phenytoin decreases levels of sorafenib by increasing metabolism. Use Caution/Monitor.

sparsentan will decrease the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Sparsentan (a CYP2C9 inducer) decreases exposure of CYP2C9 substrates and reduces efficacy related to these substrates. sparsentan will decrease the level or effect of phenytoin by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. Sparsentan (a CYP2C19 inducer) decreases exposure of CYP2C19 substrates and reduces efficacy related to these substrates.

stiripentol will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Consider reducing the dose of CYP2C19 substrates, if adverse reactions are experienced when administered concomitantly with stiripentol.stiripentol, phenytoin.
Either increases effects of the other by sedation. Use Caution/Monitor. Concomitant use stiripentol with other CNS depressants, including alcohol, may increase the risk of sedation and somnolence.

phenytoin will decrease the level or effect of streptomycin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin decreases effects of sufentanil SL by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration of CYP3A4 inducers may decrease sufentanil levels and efficacy, possibly precipitating withdrawal syndrome in patients who have developed physical dependence to sufentanil. Discontinuation of concomitantly used CYP3A4 inducers may increase sufentanil plasma concentration.

sulfamethoxazole will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of sunitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of suvorexant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Strong CYP3A4 inducers may decrease suvorexant efficacy; if increased suvorexant dose required, do not exceed 20 mg/day

phenytoin will decrease the level or effect of tacrolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of tacrolimus by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Tacrolimus dosage requirements may be greater when administered concurrently with phenytoin.

phenytoin will decrease the level or effect of tadalafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Avoid combination in pulmonary HTN patients. For patients with ED, monitor response to tadalafil carefully because of potential for decreased effectiveness.

talquetamab will increase the level or effect of phenytoin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Talquetamab causes cytokine release syndrome (CRS) that may suppress activity of CYP enzymes, resulting in increased exposure of CYP substrates. This is more likely to occur from initiation of talquetamab step-up dosing up to 14 days after the first treatment dose and during and after CRS.

phenytoin will decrease the level or effect of tamoxifen by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of tasimelteon by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Avoid coadministration of tasimelteon with strong CYP3A4 inducers

teclistamab will increase the level or effect of phenytoin by altering metabolism. Use Caution/Monitor. Teclistamab causes release of cytokines that may suppress activity of CYP450 enzymes, resulting in increased exposure of CYP substrates. Monitor for increased concentrations or toxicities of sensitive CYP substrates. Adjust dose of CYP substrate drug as needed.

tecovirimat will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. Tecovirimat is a weak inhibitor of CYP2C8 and CYP2C19. Monitor for adverse effects if coadministered with sensitive substrates of these enzymes.

teduglutide increases levels of phenytoin by Other (see comment). Use Caution/Monitor.
Comment: Teduglutide may increase absorption of concomitant PO medications; caution with with drugs requiring titration or those with a narrow therapeutic index; dose adjustment may be necessary.

phenytoin will decrease the level or effect of temsirolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of teniposide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of terbinafine by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.phenytoin will decrease the level or effect of terbinafine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

tesamorelin will decrease the level or effect of phenytoin by altering metabolism. Modify Therapy/Monitor Closely. Monitor levels

tetracaine, phenytoin. Other (see comment). Use Caution/Monitor.
Comment: Monitor for signs of methemoglobinemia when methemoglobin-inducing drugs are coadministered.

phenytoin will decrease the level or effect of theophylline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of tiagabine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin decreases levels of ticagrelor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Avoid use of ticagrelor with potent CYP3A inducers.

tinidazole will increase the level or effect of phenytoin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. During concurrent therapy, consider monitoring clinical response to tinidazole and signs/symptoms of phentyoin toxicity (eg, nystagmus, ataxis, dysarthria, and lethargy)phenytoin will decrease the level or effect of tinidazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of tipranavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

tirzepatide decreases levels of phenytoin by Other (see comment). Use Caution/Monitor.
Comment: GLP1 agonists delay gastrc emptying and may impact the absorption of concomitantly administered oral medications. Monitor patients on oral medications dependent on threshold concentrations for efficacy and those with a narrow therapeutic index. .

phenytoin will decrease the level or effect of tobramycin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin will decrease the level or effect of tofacitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Loss of, or decreased response to tofacitinib may occur when coadministered with potent CYP3A4 inducers

phenytoin will decrease the level or effect of tolterodine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of tolvaptan by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin decreases levels of topiramate by increasing metabolism. Use Caution/Monitor.

phenytoin decreases levels of toremifene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. CYP3A4 inducers increase rate of toremifene metabolism, lowering the steady-state concentration in serum.

phenytoin will decrease the level or effect of tramadol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Decreased AUC of tramadol and the active metabolite (O-desmethyltramadol) when coadministered with strong CYP3A4 and CYP2B6 inducers

treosulfan decreases levels of phenytoin by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.treosulfan decreases levels of phenytoin by increasing metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of triamcinolone acetonide injectable suspension by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of triazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

triclabendazole will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C19 metabolism. Use Caution/Monitor. If plasma concentrations of the CYP2C19 substrates are elevated during triclabendazole, recheck plasma concentration of the CYP2C19 substrates after discontinuation of triclabendazole.

trofinetide will increase the level or effect of phenytoin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor CYP3A4 substrates for which a small increase in plasma concentration may lead to serious toxicities if coadministered with trofinetide (a weak CYP3A4 inhibitor).

ustekinumab, phenytoin. Other (see comment). Use Caution/Monitor.
Comment: Formation of CYP450 enzymes can be altered by increased levels of certain cytokines during chronic inflammation; thus, normalizing the formation of CYP450 enzymes. Upon initiation or discontinuation of ustekinumab in patients who are receiving concomitant CYP450 substrates, particularly those with a narrow therapeutic index, consider monitoring for therapeutic effect.

phenytoin and valoctocogene roxaparvovec both increase Other (see comment). Use Caution/Monitor. Medications that may cause hepatotoxicity when combined with valoctogene roxaparvovec may potentiate the risk of elevated liver enzymes. Closely monitor these medications and consider alternative medications in case of potential drug interactions.

valproic acid will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

vanzacaftor/tezacaftor/deutivacaftor increases levels of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor. Deutivacaftor inhibits CYP2C9 in vitro. Caution advised if coadministered with CYP2C9 substrates.

phenytoin will decrease the level or effect of vardenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin decreases effects of vecuronium by pharmacodynamic antagonism. Modify Therapy/Monitor Closely. Monitor closely for more rapid recovery from neuromuscular blockade than expected; infusion rate requirements may be higher.

phenytoin decreases levels of vemurafenib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

phenytoin will decrease the level or effect of verapamil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin will decrease the level or effect of vilanterol/fluticasone furoate inhaled by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

phenytoin decreases levels of vilazodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Consider increasing vilazodone dose up to 2-fold (not to exceed 80 mg/day) when coadministered with strong CYP3A4 inducers for >14 days.

viloxazine will increase the level or effect of phenytoin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Viloxazine (a weak CYP3A4 inhibitor) may increase systemic exposure of sensitive CYP3A4 substrates. Monitor and adjust dose of substrate as clinically indicated.

vinblastine decreases levels of phenytoin by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.vinblastine decreases levels of phenytoin by increasing metabolism. Use Caution/Monitor.vinblastine will decrease the level or effect of phenytoin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Concurrent use of vinblastine and phenytoin may reduce phenytoin plasma levels and increase seizure activity.

vincristine decreases levels of phenytoin by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.vincristine decreases levels of phenytoin by increasing metabolism. Use Caution/Monitor.

vincristine liposomal decreases levels of phenytoin by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.vincristine liposomal decreases levels of phenytoin by increasing metabolism. Use Caution/Monitor.

vindesine decreases levels of phenytoin by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.vindesine decreases levels of phenytoin by increasing metabolism. Use Caution/Monitor.

vinorelbine decreases levels of phenytoin by inhibition of GI absorption. Applies only to oral form of both agents. Use Caution/Monitor.vinorelbine decreases levels of phenytoin by increasing metabolism. Use Caution/Monitor.

phenytoin decreases effects of vitamin D by Other (see comment). Use Caution/Monitor.
Comment: Vitamin D supplementation or dosage adjustments may be required in patients who are receiving chronic treatment with anticonvulsants.

voriconazole will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.phenytoin decreases levels of voriconazole by increasing metabolism. Modify Therapy/Monitor Closely.

phenytoin increases levels of vortioxetine by increasing metabolism. Modify Therapy/Monitor Closely. Consider increasing the vortioxetine dose when coadministered with strong CYP inducers for >14 days; not to exceed 3 times original vortioxetine dose.

phenytoin will decrease the level or effect of warfarin by affecting hepatic enzyme CYP2C9/10 metabolism. Modify Therapy/Monitor Closely.

zafirlukast will increase the level or effect of phenytoin by affecting hepatic enzyme CYP2C9/10 metabolism. Use Caution/Monitor.

phenytoin decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.

phenytoin decreases levels of acetaminophen IV by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.

phenytoin decreases levels of acetaminophen rectal by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.

acetazolamide, phenytoin. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Increased risk of anticonvulsant induced osteomalacia.

phenytoin will decrease the level or effect of alfentanil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of alfuzosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of alosetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of alvimopan by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.

phenytoin will decrease the level or effect of ambrisentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of armodafinil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.phenytoin will decrease the level or effect of armodafinil by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.

phenytoin decreases effects of atracurium by pharmacodynamic antagonism. Minor/Significance Unknown.

auranofin increases levels of phenytoin by unspecified interaction mechanism. Minor/Significance Unknown.

phenytoin decreases levels of biotin by unspecified interaction mechanism. Minor/Significance Unknown. Biotin supplementation may be necessary.

phenytoin will decrease the level or effect of bosentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

brinzolamide, phenytoin. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Increased risk of anticonvulsant induced osteomalacia.

carbamazepine, phenytoin. Mechanism: unspecified interaction mechanism. Minor/Significance Unknown. Carbamazepine may increase or decrease phenytoin levels.

phenytoin decreases levels of caspofungin by increasing metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of cevimeline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of clarithromycin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

clopidogrel increases levels of phenytoin by decreasing metabolism. Minor/Significance Unknown.

phenytoin decreases levels of cyanocobalamin by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

phenytoin will decrease the level or effect of dapsone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

dexmethylphenidate increases effects of phenytoin by decreasing metabolism. Minor/Significance Unknown.

diazoxide decreases levels of phenytoin by increasing metabolism. Minor/Significance Unknown.

disulfiram increases levels of phenytoin by decreasing metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of docetaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of donepezil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin decreases levels of doxycycline by increasing metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of dutasteride by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of eplerenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

ethosuximide increases effects of phenytoin by pharmacodynamic synergism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of eucalyptus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin decreases levels of ezogabine by Mechanism: unknown. Minor/Significance Unknown. Upon discontinuation of phenytoin, ezogabine clearance decreased by approximately 30%. Consider an increase in the ezogabine dose during concurrent use.

phenytoin will decrease the level or effect of fexofenadine by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.

phenytoin will decrease the level or effect of finasteride by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

folic acid decreases levels of phenytoin by increasing metabolism. Minor/Significance Unknown. Large doses of folic acid (>10 mg/day).

phenytoin decreases levels of furosemide by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

grapefruit, phenytoin. Other (see comment). Minor/Significance Unknown.
Comment: Grapefruit juice has been determined to have no effect on the pharmacokinetics of phenytoin.

phenytoin, immune globulin IM (IGIM). Mechanism: unknown. Minor/Significance Unknown. Risk of hypersensitivity myocarditis.

phenytoin, immune globulin IV (IGIV). Mechanism: unknown. Minor/Significance Unknown. Risk of hypersensitivity myocarditis.

phenytoin, immune globulin SC. Mechanism: unknown. Minor/Significance Unknown. Risk of hypersensitivity myocarditis (theoretical interaction, based on IM and IV immune globulin).

influenza virus vaccine quadrivalent, phenytoin. Mechanism: unknown. Minor/Significance Unknown. Vaccine administration may incr or decr phenytoin levels.

influenza virus vaccine quadrivalent, cell-cultured, phenytoin. Mechanism: unknown. Minor/Significance Unknown. Vaccine administration may incr or decr phenytoin levels.

influenza virus vaccine trivalent, phenytoin. Mechanism: unknown. Minor/Significance Unknown. Vaccine administration may incr or decr phenytoin levels.

influenza virus vaccine trivalent, recombinant, phenytoin. Mechanism: unknown. Minor/Significance Unknown. Vaccine administration may incr or decr phenytoin levels.

isoniazid increases levels of phenytoin by decreasing metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of isradipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of itraconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of ketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

L-methylfolate decreases levels of phenytoin by increasing metabolism. Minor/Significance Unknown.

phenytoin decreases levels of levocarnitine by unspecified interaction mechanism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of levoketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin decreases levels of levothyroxine by increasing metabolism. Minor/Significance Unknown.phenytoin decreases levels of levothyroxine by plasma protein binding competition. Minor/Significance Unknown.

phenytoin, lily of the valley.
Either increases toxicity of the other by pharmacodynamic synergism. Minor/Significance Unknown.

phenytoin decreases levels of liothyronine by increasing metabolism. Minor/Significance Unknown.phenytoin decreases levels of liothyronine by plasma protein binding competition. Minor/Significance Unknown.

phenytoin increases toxicity of lithium by unknown mechanism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of loratadine by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.

phenytoin decreases levels of meperidine by increasing metabolism. Minor/Significance Unknown.

methazolamide, phenytoin. Mechanism: pharmacodynamic synergism. Minor/Significance Unknown. Increased risk of anticonvulsant induced osteomalacia.

methsuximide increases effects of phenytoin by pharmacodynamic synergism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of montelukast by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

mycophenolate increases effects of phenytoin by plasma protein binding competition. Minor/Significance Unknown. Mycophenolate decreased phenytoin protein binding from 90% to 87% in vitro. The clinical significance of this interaction is unknown. .

phenytoin will decrease the level or effect of nimodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of nitrendipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin decreases levels of oxcarbazepine by increasing metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of paclitaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of paclitaxel protein bound by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of parecoxib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenobarbital decreases levels of phenytoin by increasing metabolism. Minor/Significance Unknown. Phenobarbital may occasionally not change or even increase (via competitive inhibition) phenytoin levels.

phenytoin will decrease the level or effect of pimozide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of pioglitazone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of propafenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

pyridoxine decreases levels of phenytoin by increasing metabolism. Minor/Significance Unknown. High dose of pyridoxine (vitamin B6), >=200 mg/day.

pyridoxine (Antidote) decreases levels of phenytoin by increasing metabolism. Minor/Significance Unknown. High dose of pyridoxine (vitamin B6), >=200 mg/day.

pyrimethamine decreases effects of phenytoin by pharmacodynamic antagonism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of rabeprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown. Consider alternative for one of the interacting drugs

phenytoin will decrease the level or effect of ramelteon by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin decreases effects of rapacuronium by pharmacodynamic antagonism. Minor/Significance Unknown.

rifabutin decreases levels of phenytoin by increasing metabolism. Minor/Significance Unknown.

sage decreases effects of phenytoin by pharmacodynamic antagonism. Minor/Significance Unknown. Theoretical interaction; some species of sage may cause convulsions.

phenytoin will decrease the level or effect of saxagliptin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

serdexmethylphenidate/dexmethylphenidate increases effects of phenytoin by decreasing metabolism. Minor/Significance Unknown.

phenytoin decreases effects of succinylcholine by pharmacodynamic antagonism. Minor/Significance Unknown.

sucralfate decreases levels of phenytoin by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

phenytoin will decrease the level or effect of sufentanil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

sulfadiazine increases levels of phenytoin by decreasing metabolism. Minor/Significance Unknown.

sulfamethoxazole increases levels of phenytoin by decreasing metabolism. Minor/Significance Unknown.

sulfisoxazole increases levels of phenytoin by decreasing metabolism. Minor/Significance Unknown.

phenytoin decreases levels of thyroid desiccated by increasing metabolism. Minor/Significance Unknown.phenytoin decreases levels of thyroid desiccated by plasma protein binding competition. Minor/Significance Unknown.

phenytoin decreases levels of tiagabine by increasing metabolism. Minor/Significance Unknown.

phenytoin decreases levels of tibolone by increasing metabolism. Minor/Significance Unknown. Theoretical interaction.

topiramate increases levels of phenytoin by decreasing metabolism. Minor/Significance Unknown.

phenytoin decreases levels of toremifene by increasing metabolism. Minor/Significance Unknown.

trazodone increases levels of phenytoin by unspecified interaction mechanism. Minor/Significance Unknown.

phenytoin decreases levels of typhoid polysaccharide vaccine by increasing metabolism. Minor/Significance Unknown.

phenytoin decreases levels of typhoid vaccine live by increasing metabolism. Minor/Significance Unknown.

valproic acid, phenytoin. Mechanism: plasma protein binding competition. Minor/Significance Unknown. Valproic acid may increase or decrease phenytoin levels.phenytoin decreases levels of valproic acid by increasing metabolism. Minor/Significance Unknown.

vigabatrin decreases levels of phenytoin by unknown mechanism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of vinblastine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.phenytoin will decrease the level or effect of vinblastine by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown. Phenytoin may be less likely to interact with vinblastine. Careful monitoring of patients for seizure activity is recommended, as is monitoring of plasma phenytoin levels.

phenytoin will decrease the level or effect of vincristine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.phenytoin will decrease the level or effect of vincristine by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown. Plasma concentrations and therapeutic effect of Phenytoin may be reduced by Vincristine. Frequency of seizures may be increased.

phenytoin will decrease the level or effect of vincristine liposomal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.phenytoin will decrease the level or effect of vincristine liposomal by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown. Plasma concentrations and therapeutic effect of Phenytoin may be reduced by Vincristine. Frequency of seizures may be increased.

phenytoin will decrease the level or effect of vinorelbine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of zaleplon by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of ziprasidone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of zolpidem by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

phenytoin will decrease the level or effect of zonisamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.