Differential properties of enantiomers of commercially available racemates.

The existence of left- or right-handedness of a compound is referred to as chirality. Each form (left- or right-handed) of a chiral compound is called an 'enantiomer' or an 'isomer'. A collection containing only one enantiomeric form of a chiral molecule is called an optically pure, chirally pure, enantiomerically pure or unichiral compound while collection of equal amounts of the two enantiomeric forms (R and S) is called a racemate. Many of the drugs currently used in medical practice are racemates. However it is well documented that the two enantiomers of a racemate can differ in their pharmacokinetic/pharmacodynamic and efficacy/ safety profiles. Replacing existing racemates with unichiral drugs may result in improved safety and/or efficacy profile of various racemates. This article presents an overview of differential properties of enantiomers of some commercially available racemates.