Atorvastatin exists in four optical forms. The (3R, 5R)-atorvastatin enantiomer displays the greatest activity against HMG-CoA reductase. (3S,5S)-Atorvastatin is an enantiomer of atorvastatin with little or no inhibitory activity against HMG-CoA reductase [1]. Atorvastatin is a synthetic HMG-CoA reductase inhibitor implicated in lowering plasma cholesterol levels by inhibiting endogenous cholesterol synthesis. Atorvastatin also reduces triglyceride levels through an as yet unproven mechanism [2]. In various trials in patients with hypercholesterolaemia, atorvastatin produced greater reductions in total cholesterol, apolipoprotein B, LDL-cholesterol and triglyceride levels. In patients with primary hypercholesterolaemia, atorvastatin in combination with colestipol produced significant reductions in LDL-cholesterol levels and smaller reductions in triglyceride levels than atorvastatin monotherapy [2].
References:
[1] Kocarek T A, Dahn M S, Cai H, et al. Regulation of CYP2B6 and CYP3A expression by hydroxymethylglutaryl coenzyme A inhibitors in primary cultured human hepatocytes[J]. Drug Metabolism and Disposition, 2002, 30(12): 1400-1405.
[2] Lea A P, McTavish D. Atorvastatin[J]. Drugs, 1997, 53(5): 828-847.