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Warfarin and antibiotics — GPhC CRA MCQ

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ModerateDrug InteractionsWarfarin and antibioticsGPhC CRA

A man taking warfarin is prescribed doxycycline for a chest infection. He asks whether his INR needs checking. What monitoring is required?

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Correct answer: B — Arrange or advise closer INR monitoring during and after the antibiotic course

Several antibiotics can alter INR in patients taking warfarin through effects on metabolism, gut flora or illness. Closer INR monitoring is often appropriate. Warfarin dose changes should be guided by anticoagulation services.

Reference: BNF