Carbamazepine‐induced acceleration of diphenylhydantoin and warfarin metabolism in man

Abstract

Diphenylhydantoin half‐life was determined in 5 patients before and during treatment with carbamazepine. It caused a significant decrease in the diphenylhydantoin half‐life from 10.6 hours to 6.4 hours. Seven patients who for a period had been given diphenylhydantoin were also started on carbamazepine. This resulted in a fall in serum diphenylhydantoin levels in 3 of the patients. Alterations in warfarin half‐life, serum warfarin, and plasma prothrombin‐proconvertin concentration during carbamazepine treatment were compatible with a stimulation of warfarin metabolism. The effect of carbamazepine on diphenylhydantoin and warfarin metabolism is probably explained by an induction of the drug‐metabolizing enzyme system in the liver.