Switching from Simvastatin 40 mg to Rosuvastatin
Switch to rosuvastatin 5 mg once daily, which provides equivalent or slightly greater LDL-lowering than simvastatin 40 mg while maintaining your current excellent lipid control.
Rationale for Rosuvastatin 5 mg
Simvastatin 40 mg achieves approximately 35–41% LDL-C reduction, classifying it as moderate-intensity therapy 1, 2.
Rosuvastatin 5 mg produces 39–45% LDL-C reduction, also moderate-intensity therapy, making it the appropriate equivalent dose 1, 3.
Your current LDL-C of 66 mg/dL on simvastatin 40 mg indicates excellent response; rosuvastatin 5 mg will maintain this control without over-treatment 1.
Rosuvastatin demonstrates superior potency on a milligram-per-milligram basis—approximately double that of simvastatin—so a lower milligram dose achieves comparable or better LDL-C reduction 1, 4.
Why Not Higher Doses
Rosuvastatin 10 mg would provide 44–52% LDL-C reduction, which is unnecessary given your LDL-C is already well below most treatment targets 1, 3.
Rosuvastatin 20–40 mg constitutes high-intensity therapy (≥50% LDL-C reduction) and is reserved for patients with established cardiovascular disease, LDL-C ≥190 mg/dL, or diabetes with additional risk factors—not for routine conversion when lipid goals are already met 1, 2.
Starting at a higher dose than needed increases the risk of statin-associated muscle symptoms and hepatic enzyme elevation without additional cardiovascular benefit when LDL-C is already at goal 1.
Monitoring After Conversion
Recheck a fasting lipid panel 4–12 weeks after switching to confirm LDL-C remains at or below your current level 1.
Assess for any new muscle symptoms, as individual statin tolerance can vary even when switching between agents 1.
If LDL-C rises above 100 mg/dL (unlikely given your current excellent control), consider increasing to rosuvastatin 10 mg 1.
Special Considerations
If you have severe renal impairment (CrCl <30 mL/min), rosuvastatin should not exceed 10 mg daily, but simvastatin requires no renal dose adjustment; discuss this with your physician if applicable 1.
Asian patients should start at rosuvastatin 5 mg due to increased plasma concentrations, making this the appropriate starting dose regardless of prior simvastatin dose 5.
Rosuvastatin can be taken at any time of day, with or without food, providing dosing flexibility 5.