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Diltiazem and simvastatin dose limit — GPhC CRA MCQ

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ModerateDrug InteractionsDiltiazem and simvastatin dose limitGPhC CRA

A patient taking diltiazem modified-release is prescribed simvastatin 40 mg nightly. The pharmacy system flags a dose issue. What is the most important interaction to flag?

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

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Correct answer: A — Diltiazem increases simvastatin exposure, so simvastatin dose should be limited or changed

Diltiazem inhibits CYP3A4 and can increase simvastatin levels, raising myopathy risk. BNF dose limits or alternative statins should be considered. Administration time does not overcome the metabolic interaction.

Reference: BNF