skip to main content

Miconazole-warfarin interaction — GPhC CRA MCQ

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

ModerateDrug InteractionsMiconazole-warfarin interactionGPhC CRA

A 35-year-old woman on warfarin presents with a new prescription for miconazole oral gel for oral thrush. What is the most appropriate action?

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

Reveal the answer and explanation

Correct answer: D — Contact the prescriber as miconazole oral gel can significantly increase the INR even when used topically in the mouth

Miconazole oral gel, despite being applied topically in the mouth, has significant systemic absorption and is a potent inhibitor of CYP2C9. It can markedly increase the INR in patients on warfarin, leading to serious bleeding risk. The BNF lists this as a clinically significant interaction. The prescriber should be contacted to discuss an alternative such as nystatin oral suspension, which does not interact with warfarin.

Reference: BNF Drug Interactions; MHRA