This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Adverse Drug Effect, Subject name: Pharmacology
[{'content': 'All of the following drugs increase bleeding when given to a patient on warfarin EXCEPT: \nSelect and explain. \nA. Isoniazid, B. Amiodarone, C. Carbamazepine, D. Cimetidine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C. CarbamazepineWarfarin constitutes S as well as R enantiomers. S Warfarin is the most active form:* Metabolism of S warfarin is by CYP2C9 leading to the formation of 7-OH warfarin* Metabolism of R warfarin is by CYP1A1, CYP1A2, CYP3A4 leading to the formation of 6-OH warfarin, 8-OH warfarin, 10-OH warfarinAs Carbamazepine is enzyme inducer, it induces metabolism of warfarin and hence warfarin concentration decreases and it can lead to therapeutic failureRest of drugs: Isoniazid, Amiodarone, cimetidine are microsomal enzyme inhibitors leading to warfarin toxicity and can lead to bleeding.', 'role': 'assistant'}]