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Simvastatin and clarithromycin — GPhC CRA MCQ

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ModerateDrug InteractionsSimvastatin and clarithromycinGPhC CRA

A patient taking simvastatin 40 mg nightly presents a prescription for clarithromycin 500 mg twice daily. He asks whether he should continue his regular medicines as usual. What is the most important interaction to flag?

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Correct answer: C — Clarithromycin can increase simvastatin exposure and myopathy risk

Clarithromycin is a strong inhibitor of CYP3A4 and can markedly increase simvastatin concentrations. This increases the risk of myopathy and rhabdomyolysis. The pharmacist should query management, such as temporarily withholding simvastatin or selecting an alternative antibiotic where appropriate. The interaction is not a simple absorption issue.

Reference: BNF