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Warfarin and miconazole — GPhC CRA MCQ

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HardDrug InteractionsWarfarin and miconazoleGPhC CRA

A 68-year-old man takes warfarin for a mechanical heart valve and attends with an NHS prescription for miconazole oral gel for denture stomatitis. His last INR was 2.8 two weeks ago and he has no bleeding. The prescriber has not added any monitoring instructions. What is the most important interaction to flag?

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Correct answer: C — Miconazole can markedly increase INR and bleeding risk with warfarin

Miconazole, including oral gel, is a clinically important interaction with warfarin because it can inhibit warfarin metabolism and raise INR. A mechanical valve makes anticoagulation safety particularly important. The pharmacist should contact the prescriber to consider an alternative and arrange INR monitoring if exposure has occurred.

Reference: BNF; MHRA Drug Safety Update