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Clarithromycin and simvastatin — GPhC CRA MCQ

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ModerateDrug InteractionsClarithromycin and simvastatinGPhC CRA

A 72-year-old man presents a prescription for clarithromycin 500mg twice daily for 7 days. His repeat medicines include simvastatin 40mg at night, amlodipine 5mg daily and aspirin 75mg daily. He reports previous muscle pains on lipid treatment. What is the most important interaction to flag?

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Correct answer: D — clarithromycin can increase simvastatin exposure and risk of myopathy

Clarithromycin inhibits CYP3A4 and can markedly increase simvastatin concentrations. The combination increases the risk of myopathy and rhabdomyolysis, especially in an older patient with previous muscle symptoms. The prescriber should be contacted to withhold simvastatin temporarily or use a suitable alternative antibiotic. Aspirin is not the key interaction in this scenario.

Reference: BNF