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Clarithromycin and simvastatin — GPhC CRA MCQ

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HardDrug InteractionsClarithromycin and simvastatinGPhC CRA

A 62-year-old man taking simvastatin 40mg at night is prescribed clarithromycin 500mg twice daily for pneumonia. He has CKD stage 3 and reports previous muscle aches with statins. The prescription is due to start today. What is the most important interaction to flag?

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Correct answer: A — Clarithromycin increases simvastatin exposure and myopathy risk

Clarithromycin inhibits CYP3A4 and can substantially increase simvastatin concentrations. CKD and a history of muscle symptoms increase the clinical importance of the interaction. The prescriber should be contacted to withhold simvastatin temporarily or choose a suitable alternative antibiotic.

Reference: BNF