DRUG CHIRALITY, ITS SIGNIFICANCE IN VETER INARY PHARMACOLOGY AND THERAPEUTICS

The definitions and rules of nomenclature in stereochemistry are recal led, as well as the rationale of the methods for the analytical resolu tion of enantiomers. The interest of chiral pharmacology in animals is illustrated by examples selected among sulfur-containing antiparasiti c drugs and 2-arylpropionate NSAIDs. In metabolic reactions of sulfoxi dation, the product stereoselectivity is opposed depending on the enzy me responsible : a cytochrome or a flavine-monooxygenase (albendazole) or different isoenzymes of the cytochromes P450 (toltrazuril). For me tabolic chiral inversion of 2-arylpropionates, the substrate stereospe cificity of acyl-CoA-ligase is observed for the (-)(R)-enantiomer. The interspecies diversity in chiral metabolic behaviors which is to be c orrelated to pharmacodynamics, is interpreted in the light of in vivo and in vitro enzymatic investigations.