Nonchiral, homochiral and composite chiral drugs

Chirality and the implicit stereoselectivity in pharmacodynamics and pharmacokinetics, in particular of racemic therapeutics, are interesting from both scientific and applied points of view. There is much literature on the subject, including a series of papers on chirality in TiPS in 1986 (Vol. 7, pp. 20-23, 60-64, 112-116, 155-158, 200-205 and 281-285). The choice between single stereoisomers (homochiral drugs) and composite chiral drugs (mixtures of stereoisomers) depends upon therapeutic advantages (such as a reduction in xenobiotic load), possible adverse side-effects and development costs. There is a need for critical evaluation of existing and new composite chiral drugs, while the potential of nonchiral drugs is hardly discussed in the literature. This review by E. J. Ariëns considers current information on composite, homo- and nonchiral drugs, with particular regard to drug development.