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©2013 UpToDate ® Print Email Antiepileptic drug-nonantiepileptic drug interactions Nonantiepileptic drug Antiepileptic drug Outcome of drug interaction Antacids Phenobarbital, phenytoin, carbamazepine, and gabapentin Reduced gut absorption of the AEDs Anticancer agents Enzyme-inducing AEDs (eg, carbamazepine, phenytoin, phenobarbital and others, see text) AEDs can increase the metabolism of anticancer agents and reduce therapeutic efficacy Antiviral agents that are metabolized by CYP3A4 Enzyme-inducing AEDs (eg, carbamazepine, phenytoin, phenobarbital and others, see text) AEDs can increase the metabolism and reduce the plasma concentrations of antiviral agents Benzodiazepines Carbamazepine, phenytoin, and phenobarbital Increases metabolism and decreases plasma concentrations of benzodiazepines Cimetidine Phenytoin Inhibition of phenytoin metabolism Clarithromycin Carbamazepine Inhibition of AED metabolism and increased plasma concentrations of carbamazepine Corticosteroids Enzyme-inducing AEDs (eg, carbamazepine, phenytoin, phenobarbital and others, see text) Increased metabolism of the corticosteroid Cyclosporine Enzyme-inducing AEDs (eg, carbamazepine, phenytoin, phenobarbital and others, see text) AEDs can increase the metabolism and reduce the plasma concentrations of cyclosporine Digoxin Phenytoin, topiramate Decreased plasma concentrations of digoxin Erythromycin Carbamazepine Inhibition of the metabolism of the AEDs and increased plasma concentrations Fluconazole Phenytoin Inhibition of phenytoin metabolism with a possible increase in phenytoin plasma concentrations Fluoxetine Carbamazepine and phenytoin Inhibition of AED metabolism and increased plasma concentrations of carbamazepine and phenytoin Griseofulvin Enzyme-inducing AEDs (eg, carbamazepine, phenytoin, phenobarbital and others, see text) Increased metabolism of griseofulvin and reduced plasma concentrations Haloperidol Enzyme-inducing AEDs (eg, carbamazepine, phenytoin, phenobarbital and others, see text) Increased metabolism of haloperidol with a subsequent decrease in plasma concentration Omeprazole Phenytoin Inhibition of phenytoin metabolism Oral contraceptive pill Enzyme-inducing AEDs (eg, carbamazepine, phenytoin, phenobarbital, felbamate, oxcarbazepine, perampanel and topiramate) Increased metabolism of the contraceptive pill and reduced hormone levels Propofol Valproate Valproate reduces the dose of propofol required for sedation* Sertraline Lamotrigine Inhibition of AED metabolism and increased plasma concentrations of lamotrigine St. John's wort

Enzyme-inducing AEDs (eg, carbamazepine, phenytoin, phenobarbital, felbamate, oxcarbazepine, perampanel and topiramate) Increased metabolism of the contraceptive pill and reduced hormone levels Propofol Valproate Valproate reduces the dose of propofol required for sedation* Sertraline Lamotrigine Inhibition of AED metabolism and increased plasma concentrations of lamotrigine St. John's wort Carbamazepine, phenytoin, perampanel The metabolism of carbamazepine, phenytoin and perampanel may be increased by St. John's wort Theophylline Enzyme-inducing AEDs (eg, carbamazepine, phenytoin, phenobarbital and others, see text) Increased metabolism of theophylline Tricyclic antidepressants (TCAs) Enzyme-inducing AEDs (eg, carbamazepine, phenytoin, phenobarbital and others, see text) Bidirectional interaction with TCA concentrations reducing and AED concentrations increasing Warfarin Enzyme-inducing AEDs (eg, carbamazepine, phenytoin, phenobarbital and others, see text) Increased metabolism of warfarin and reduced anticoagulant activity *Ishii M, Higuchi H, Maeda S, et al. The influence of oral VPA on the required dose of propofol for sedation during dental treatment in patients with mental retardation: A prospective observer-blinded cohort study. Epilepsia 2012, 53:e13. Reproduced with permission from: Patsalos PN, Froscher W, Pisani F, van Rijn CM, Epilepsia 2002; 43:365.