Drug Interaction Report

ADJUST DOSE: Coadministration of eslicarbazepine acetate and phenytoin may decrease the systemic exposure to the active metabolite, eslicarbazepine, and increase the exposure to phenytoin. The proposed mechanisms are induction of glucuronidation by phenytoin and inhibition of CYP450 2C19 metabolism by eslicarbazepine. In healthy study subjects administered eslicarbazepine acetate 1200 mg once daily with phenytoin, eslicarbazepine systemic exposure (AUC) decreased by an average of 31% to 33% and phenytoin AUC increased by 31% to 35%.

MANAGEMENT: Close observation for clinical and laboratory evidence of altered effects is recommended during concomitant use of eslicarbazepine acetate and phenytoin, particularly when one drug is started or discontinued. Patients should be advised to contact their physician if they experience loss of seizure control or signs and symptoms of phenytoin toxicity such as nausea, vomiting, tremors, ataxia, lethargy, slurred speech, visual disturbances, or changes in mental status. A dosage increase for eslicarbazepine acetate and/or dosage reduction for phenytoin may be required based on efficacy and tolerability.