A 56-year-old man has recently been prescribed atorvastatin. You are reviewing his medication record. Which of the following drugs increases the risk of atorvastatin toxicity?

• A. Amoxicillin
• B. Grapefruit juice
• C. Erythromycin
• D. Ciclosporin

Answer: (D)

Atorvastatin is cleared mainly by the liver enzyme CYP3A4, so when this enzyme is inhibited, the statin stays in the body longer and at higher levels, increasing the risk of muscle toxicity. Ciclosporin is a strong inhibitor of CYP3A4 and P-glycoprotein, which markedly raises atorvastatin exposure and the chance of adverse effects like myopathy or rhabdomyolysis. Amoxicillin doesn’t affect statin metabolism; grapefruit juice can modestly increase statin levels by reducing intestinal CYP3A4, and macrolide antibiotics like erythromycin can also raise levels, but the combination with ciclosporin is the most significant risk in this scenario.