4 known interactions • 2 major • 2 moderate • 0 minor
Always disclose all medications to your healthcare providers — prescription medicines, OTC medications, vitamins, and herbal supplements. This list may not include every possible interaction. Use our Medicine Interaction Checker to screen your complete medication list.
Potentially life-threatening or causing permanent damage. Avoid combination.
May worsen condition or require dose adjustment. Monitor closely.
Usually limited clinical effect. Manage with routine monitoring.
CYP3A4 inhibitors (amiodarone, amlodipine, diltiazem, verapamil, azole antifungals, clarithromycin, HIV protease inhibitors)
Simvastatin is metabolized by CYP3A4; inhibitors markedly increase simvastatin acid levels, dramatically increasing myopathy and rhabdomyolysis risk. Lovastatin has the same vulnerability.
Management: With amiodarone/amlodipine: max 20mg/day. With verapamil/diltiazem: max 10mg/day. With strong CYP3A4 inhibitors (azole antifungals, clarithromycin, protease inhibitors): CONTRAINDICATED.
Gemfibrozil / niacin
Additive myopathy risk. Gemfibrozil inhibits simvastatin glucuronidation, increasing levels.
Management: Avoid simvastatin + gemfibrozil. If fibrate needed, use fenofibrate (lower myopathy risk). Limit niacin to ≤1g/day.
Warfarin
Simvastatin can increase warfarin's anticoagulant effect (INR increase).
Management: Monitor INR when starting simvastatin or changing doses.
Colchicine
Increased myopathy risk with combination — both agents affect muscle function.
Management: Monitor for myopathy symptoms if combination unavoidable.
Always ask your pharmacist about potential interactions with food, alcohol, and supplements specific to Simvastatin. Some medicines have significant interactions with grapefruit juice, high-fat meals, dairy products, or vitamin K-rich foods.