Interaction Between Antiepileptic Drug and Warfarin from Anticoagulation Clinic:A Two-case Report and Review of Literature / 医药导报

ABSTRACT

Objective To explore the interaction between warfarin and antiepileptic drugs such as carbamazepine and oxcarbazepine.Methods A 78-year-old woman suffered from warfarin resistance after initial warfarin dosing for several days.Based on her medication review,clinical pharmacist found that the warfarin resistance resulted from co-administered carbamazepine.Her warfarin dosage was increased,and the international normalized ratio (INR) increased to the target range.Another woman had been taking warfarin therapy for long time with a stable maintenance dose.She consulted clinical pharmacist for the influence of co-administered oxcarbazepine on warfarin.The patient was advised to maintain the dose and monitor her INR more closely.Her INR did not fluctuate.Results Carbamazepine induced warfarin metabolism.As a result,the patient needed increased dosage of warfarin to maintain the INR in the therapeutic target range.Oxcarbazepine does not induce liver enzymes,and therefore the INR did not fluctuate.Conclusion Carbamazepine may reduce the efficacy of warfarin.Oxcarbazepine offers a clinical advantage over carbamazepine,especially when co-administration of warfarin is required.