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Warfarin and metronidazole — GPhC CRA MCQ

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HardDrug InteractionsWarfarin and metronidazoleGPhC CRA

A 67-year-old man stable on warfarin is prescribed metronidazole 400mg three times daily for dental infection. His last INR was 2.6 and he has no bleeding. What monitoring is required?

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Correct answer: DINR and symptoms of bleeding during and after the antibiotic course

Metronidazole can enhance the anticoagulant effect of warfarin and increase INR. The patient should have anticoagulation clinic or prescriber advice about INR monitoring and bleeding symptoms. The effect can be clinically significant even with short courses. The other monitoring options do not assess warfarin safety.

Reference: BNF