Clinically Significant Hemorrhage Due to Warfarin-Carbamazepine Interaction

Abstract

A 61-year-old woman receiving warfarin for postoperative atrial fibrillation and carbamazepine for a peripheral neuropathy had extreme elevation of prothrombin time associated with clinically significant hemorrhage when the carbamazepine therapy was discontinued. The mechanism of this significant drug interaction involves the withdrawal of carbamazepine-induced enhancement of hepatic warfarin breakdown with resultant delay of warfarin excretion and excessive hypoprothrombinemia. The clinically significant hemorrhage associated with warfarin-carbamazepine interaction is an indication for caution when these two agents are prescribed concomitantly.