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Rifampicin and warfarin — GPhC CRA MCQ

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ModerateDrug InteractionsRifampicin and warfarinGPhC CRA

A patient taking warfarin for a mechanical heart valve is prescribed rifampicin by a specialist clinic. The patient asks why the anticoagulation clinic has been contacted. What is the most important interaction to flag?

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Correct answer: C — Rifampicin can reduce warfarin effect through enzyme induction

Rifampicin is a potent enzyme inducer and can reduce warfarin anticoagulant effect, risking thrombosis. Close INR monitoring and dose adjustment are usually required. The interaction may persist after rifampicin is stopped.

Reference: BNF