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Warfarin and metronidazole — GPhC CRA MCQ

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ModerateCardiovascular TherapeuticsWarfarin and metronidazoleGPhC CRA

A 80-year-old woman taking warfarin for atrial fibrillation is prescribed metronidazole 400mg three times daily for dental infection. Her INR has been stable for several months. What is the most important interaction to flag?

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Correct answer: E — Metronidazole can increase INR and bleeding risk with warfarin

Metronidazole can increase the anticoagulant effect of warfarin and raise bleeding risk. The prescriber or anticoagulant service should be contacted so INR monitoring and dose adjustment can be arranged. The patient should also be counselled about bleeding symptoms.

Reference: BNF