Pharmacokinetic and pharmacodynamic consequences of stereoselective drug metabolism in man.

The examples discussed demonstrate the importance of stereoselective drug metabolism and raise the question of whether the therapeutic use of racemic drugs is still justified. There is no straightforward answer to this question. If only quantitative differences in therapeutic activity exist and the less active enantiomer is not predominantly responsible for side effects, the therapeutic benefit gained by using the more active enantiomer is only marginal and does not justify the substantial increase in costs involved in manufacturing such a drug preparation. However, if stereoselectivity in therapeutic activity is pronounced and adverse drug reactions are caused mainly by the less active isomer then an isomeric pure drug preparation should be used.