MAJOR — Use With Caution
FDA simvastatin label mandates maximum dose of 10mg/day with diltiazem. Higher doses significantly increase rhabdomyolysis risk.
Evidence level: STRONG
Diltiazem (a blood pressure and heart medication) significantly increases simvastatin levels in your blood, raising the risk of muscle damage. The FDA limits simvastatin to no more than 10mg daily if you also take diltiazem.
Diltiazem is a moderate CYP3A4 inhibitor. Increases simvastatin levels approximately 5-fold. FDA simvastatin label limits dose to 10mg daily with diltiazem.
If you take both medications, your simvastatin dose must not exceed 10mg daily. If you need more cholesterol lowering, ask about switching to a different statin (atorvastatin, rosuvastatin, pravastatin).
Take Simvastatin in the evening when cholesterol synthesis peaks (exception: atorvastatin and rosuvastatin have long half-lives and can be taken any time). Diltiazem follows its normal prescribed schedule. Report any unexplained muscle pain.
Higher risk for: those with liver impairment, genetic CYP enzyme variations (poor or ultra-rapid metabolizers), elderly, those on multiple CYP3A4 inhibitors, high-dose statin therapy, or history of myopathy.
Muscle pain, tenderness or weakness, dark urine, fever, nausea
Verify simvastatin dose does not exceed 10mg with diltiazem. Consider switching to atorvastatin or rosuvastatin which have higher dose ceilings with diltiazem.
Statin interactions often involve liver enzyme competition. Ask your doctor about alternative statins (rosuvastatin and pravastatin have fewer CYP interactions) or spacing doses 12 hours apart. CoQ10 supplementation may help with statin-related muscle discomfort.
Diltiazem (a blood pressure and heart medication) significantly increases simvastatin levels in your blood, raising the risk of muscle damage. The FDA limits simvastatin to no more than 10mg daily if you also take diltiazem.
Take Simvastatin in the evening when cholesterol synthesis peaks (exception: atorvastatin and rosuvastatin have long half-lives and can be taken any time). Diltiazem follows its normal prescribed schedule. Report any unexplained muscle pain.
Muscle pain, tenderness or weakness, dark urine, fever, nausea
Statin interactions often involve liver enzyme competition. Ask your doctor about alternative statins (rosuvastatin and pravastatin have fewer CYP interactions) or spacing doses 12 hours apart. CoQ10 supplementation may help with statin-related muscle discomfort.
Verify simvastatin dose does not exceed 10mg with diltiazem. Consider switching to atorvastatin or rosuvastatin which have higher dose ceilings with diltiazem.
Or browse the full interaction database (121,000+ pairs).