Major
amlodipine × simvastatin
Calcium channel blockers (dihydropyridines)×HMG-CoA reductase inhibitors (statins)
Mechanism
Amlodipine moderately inhibits CYP3A4 – simvastatin exposure rises 30–80 %, and the risk of myopathy and rhabdomyolysis increases.
Management
The FDA caps simvastatin at 20 mg/day when used with amlodipine. For patients needing more intensive therapy, switch to atorvastatin or rosuvastatin.
Sources
- FDA: FDA Drug Safety Communication: New restrictions, contraindications, and dose limitations for Zocor (simvastatin) to reduce the risk of muscle injury (2011)— FDA Drug Safety Communication, June 8, 2011
- Lexicomp: Lexicomp Drug Interactions (2024)— Wolters Kluwer Clinical Drug Information, Inc. Lexi-Interact Online, 2024