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Colchicine-clarithromycin fatal interaction — GPhC CRA MCQ

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HardDrug InteractionsColchicine-clarithromycin fatal interactionGPhC CRA

A 66-year-old man with CKD stage 3a (eGFR 52 mL/min/1.73m2) has been prescribed colchicine 500 micrograms twice daily for acute gout. He also takes clarithromycin 500 mg twice daily for a chest infection. What is the most important concern?

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Correct answer: C — Clarithromycin inhibits CYP3A4 and P-glycoprotein, significantly increasing colchicine levels which can cause fatal toxicity, especially in renal impairment

Clarithromycin is a potent inhibitor of CYP3A4 and P-glycoprotein. Colchicine is a substrate of both, and concurrent use can lead to dangerously elevated colchicine levels. Colchicine toxicity can be fatal, presenting with multi-organ failure. Renal impairment further increases the risk as colchicine clearance is reduced. The BNF recommends avoiding this combination. The prescriber should be contacted urgently.

Reference: BNF Drug Interactions