"... Given that cholesterol is biosynthesized in the early morning hours, the US Food and Drug Administration (FDA) has recommended evening administration for statins with shorter half-lives (lovastatin 2 hours, simvastatin < 5 hours, and fluvastatin < 3 hours). In contrast, the FDA suggested daytime administration for statins with longer half-lives (atorvastatin 14 hours, rosuvastatin 19 hours, and pravastatin 22 hours). Atorvastatin also has active metabolites with half-lives ranging from 20 to 30 hours, which may contribute to the fact that it can be taken at any time."
http://www.medscape.com/viewarticle/552756?src=mp
