Clinical pharmacokinetics and pharmacodynamics of stereoisomeric drugs

INTRODUCTION Stereoisomers may exhibit different pharmacological properties, and many drugs used in clinical practice contain one or more chiral centers. These chiral drugs are often used therapeutically either as pure stereoisomers or as a racemic mixture of equal proportions of two complementary enantiomers. The threedimensional interaction of two enantiomers with a macromolecule, such as an enzyme or receptor, to form diastereomeric complexes may result in chiral recognition and significant differences in processes such as absorption, distribution, metabolism, and excretion (pharmacokinetics or PK) as well as the time course of pharmacological response (pharmacodynamics or PD). Thus, the clinical pharmacology of chiral drugs is based on understanding the nature of these important differences for the optimization of pharmacotherapy.