skip to main content

Rifampicin and warfarin — GPhC CRA MCQ

Instant feedback + full explanation. One question, done properly.

ModerateDrug InteractionsRifampicin and warfarinGPhC CRA

A patient stable on warfarin starts rifampicin-containing treatment for tuberculosis. The TB clinic asks the community pharmacist about anticoagulation. What is the most important interaction to flag?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: B — Rifampicin can reduce warfarin effect and destabilise INR

Rifampicin is a potent enzyme inducer and can reduce warfarin anticoagulant effect, making INR control difficult. Close anticoagulation clinic involvement is required. The direction and magnitude of interaction can change when rifampicin starts or stops. Tuberculosis treatment should not be altered without specialist input.

Reference: BNF