The importance of stereoselective determination of drugs in the clinical laboratory

About 56% of the drugs currently in use are chiral compounds, and 88% of these chiral synthetic drugs are used therapeutically as racemates. Only a few of these drugs qualify for a stereospecific determination in a clinical laboratory for therapeutic drug monitoring of patients. If the qualitative and quantitative pharmacokinetic and pharmacodynamic effects are similar, the enantiomers do not need to be separated. However, if the metabolism of the different stereoisomers is handled by different enzymes which are either polymorphic or can be induced or inhibited, and if their pharmacodynamic effects have differences either in strength or in quality, enantiospecific analysis is urgently needed. Unfortunately, there are many racemic drugs where the stereospecificity of the metabolism and/or the pharmacodynamic effects of the enantiomers is not known today. For these drugs, there is a great need for studies concentrating on these differences to improve treatment of the patients.