Mr. David Lee, a 62-year-old male, presents a prescription for simvastatin 20 mg daily. His current medications include verapamil sustained-release 180 mg daily, hydrochlorothiazide 25 mg daily, and aspirin 81 mg daily. Which of the following recommendations is most appropriate for the pharmacist to provide to Mr. Lee regarding his new simvastatin prescription?

Question: Mr. David Lee, a 62-year-old male, presents a prescription for simvastatin 20 mg daily. His current medications include verapamil sustained-release 180 mg daily, hydrochlorothiazide 25 mg daily, and aspirin 81 mg daily. Which of the following recommendations is most appropriate for the pharmacist to provide to Mr. Lee regarding his new simvastatin prescription?

Answer options:

• Advise Mr. Lee to take simvastatin in the morning with food to reduce muscle discomfort. ✅ Contact the prescriber to discuss changing simvastatin to a lower dose or an alternative statin.
• Counsel Mr. Lee to monitor for signs of increased bleeding due to the combination.
• Inform Mr. Lee that simvastatin will likely reduce the effectiveness of his verapamil.

Correct answer: Contact the prescriber to discuss changing simvastatin to a lower dose or an alternative statin.

Explanation: Verapamil is a strong inhibitor of CYP3A4 and a P-gp inhibitor. Simvastatin is a substrate for CYP3A4. Co-administration of verapamil with simvastatin can significantly increase simvastatin exposure, increasing the risk of myopathy and rhabdomyolysis. It is advisable to change to a lower dose of simvastatin (max 10 mg/day) or switch to a statin not primarily metabolized by CYP3A4 (e.g., rosuvastatin or pravastatin) when used with a strong CYP3A4 inhibitor.