A dose-specific meta-analysis of lipid changes in randomized controlled trials of atorvastatin and simvastatin.

Background: The available statins exhibit differences in the potency with which they alter serum lipid levels.

Objective: Meta-analyses were conducted to assess the relative potency of atorvastatin and simvastatin (the 2 most commonly prescribed statins) across all possible dose combinations in terms of changes in total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), and high-density lipoprotein cholesterol (HDL-C).

Methods: MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, National Health Service (NHS) Centre for Reviews and Dissemination database, NHS Economic Evaluation Database, and Database of Abstracts of Reviews of Effects were searched for randomized, head-to-head trials of atorvastatin and simvastatin in patients aged >or=18 years with elevated levels of serum TC and LDL-C. Reference lists of the identified articles, letters, and editorials also were reviewed. The manufacturers of atorvastatin and simvastatin products were contacted for relevant unpublished data. All studies were reviewed and rated for quality by 2 independent reviewers. The maximum quality score was 4 points; trials with a score of <2 points were considered to be of poor quality and were excluded from analysis. Dose comparisons were abstracted in pairs from each trial. Meta-analyses were conducted on the fixed-dose pairs for each lipid parameter. Weighted mean differences in the change in TC, LDL-C, TG, and HDL-C were estimated using the Der Simonian and Laird random-effects model.

Results: Seventeen published trials and 1 unpublished study were included in the meta-analyses. Atorvastatin treatment was associated with significantly greater reductions in TC, LDL-C, and TG in the majority of dose comparisons with simvastatin. The potency of atorvastatin and simvastatin was comparable at dose ratios between 1:2 and 1:4. Higher doses of simvastatin were more effective in increasing HDL-C levels than atorvastatin, with no apparent dose-equivalence point. The HDL-C advantage of simvastatin was greatest when simvastatin 80 mg was compared with atorvastatin 80 mg (weighted mean difference, -4.35%; 95% CI, -5.64 to -3.08, P < 0.001).

Conclusions: In these meta-analyses, atorvastatin was 2 to 4 times as potent as simvastatin in reducing TC, LDL-C, and TG, indicating that the dose equivalence of atorvastatin and simvastatin lay between 1:2 and 1:4. In contrast, simvastatin was more effective than atorvastatin in increasing HDL-C, but without any indication of a point of dose equivalence.