Drug chirality: on the mechanism of R-aryl propionic acid class NSAIDs. Epimerization in humans and the clinical implications for the use of racemates.

This review summarizes and comments on the current understanding of both the biochemical and clinical implications of the epimerization of R-aryl propionic (APA) class (1) nonsteroidal anti-inflammatory agents (NSAIDs) to S-enantiomers in humans. This article focuses principally on rac-ibuprofen and its enantiomers. In the United States, five commercialized NSAIDs are APAs. Only two of them, rac-ibuprofen and rac-fenoprofen, are subject to significant epimerization in humans. The remaining three, rac-flurbiprofen, rac-ketoprofen, and S-naproxen, are not of interest in this context.