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Warfarin counselling — GPhC CRA MCQ

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HardPatient Counselling and Pharmaceutical CareWarfarin counsellingGPhC CRA

A patient with eGFR 35 mL/min/1.73 m² takes colchicine for familial Mediterranean fever and is prescribed clarithromycin. Which interpretation is correct?

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

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Correct answer: A — Avoid clarithromycin because impaired colchicine clearance risks fatal toxicity

Option A is correct: colchicine is a CYP3A4 and P-glycoprotein substrate, clarithromycin inhibits both pathways, and renal impairment further reduces colchicine clearance. The combination is contraindicated and fatal toxicity has been reported. Option C cannot prevent a metabolic and transporter interaction. Option E reverses both the mechanism and dose target. Option D monitors an irrelevant marker rather than toxicity risk. Option B does not provide treatment for familial Mediterranean fever and creates an unsafe unrelated dose change.

Reference: Colchicine SmPC: https://www.medicines.org.uk/emc/product/100968/smpc; clarithromycin SmPC: https://www.medicines.org.uk/emc/product/11562/smpc