Summary : Exposure to simvastatin and its metabolite increased by approximately 80% and 60%, respectively, with coadministration of simvastatin and amlodipine in a pharmacokinetic study. The increased simvastatin exposure increases the risk of myopathy, including rhabdomyolysis. If it is necessary to coadminister amlodipine and simvastatin, the dose of simvastatin should not exceed 20 mg/day. Patients who are stabilized on an 80-mg dose of simvastatin for more than 1 year who need to start amlodipine should be switched to a statin or statin-based regimen with less potential for drug interaction (Prod Info ZOCOR® oral tablets, 2011).