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Topical NSAID-warfarin interaction — GPhC CRA MCQ

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HardDrug InteractionsTopical NSAID-warfarin interactionGPhC CRA

A 40-year-old man presents to the pharmacy asking to buy diclofenac gel for a sports injury to his shoulder. He takes warfarin for a mechanical heart valve. He has no other medical conditions. What is the most appropriate advice?

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Correct answer: D — Supply diclofenac gel but advise him to monitor for bruising at the application site, and inform him that topical NSAIDs may have a small systemic effect that could interact with warfarin

Topical NSAIDs have significantly lower systemic absorption than oral formulations, but they are not entirely without systemic effects. In patients taking warfarin, there is a small potential for interaction that could increase bleeding risk. The pharmacist should supply with caution, advise monitoring for unusual bruising or bleeding, and suggest the patient informs his anticoagulant clinic. An absolute refusal is overly cautious, but dispensing without any warning would be inappropriate.

Reference: BNF; BNF Drug Interactions