[Pharmacokinetics of chiral drugs]

The rate and extent of passive pharmacokinetic processes, such as passive gastrointestinal absorption, tissue distribution and glomerular filtration, depend on the physical-chemical properties of a drug. In the case of chiral drugs, since enantiomers have the same properties, in general we would not expect passive processes to be stereoselective. On the contrary, enantioselectivity would occur for processes involving a drug interaction with a chiral macromolecule (e.g. receptors, enzymes, transport proteins), like the carrier-mediated absorption, protein binding, active renal and biliary secretion, metabolism. However, a few exceptions aside, the degree of stereoselectivity of these processes is relatively modest. In this paper we reviewed several examples of stereoselective kinetic processes and discussed the limits of the interpretation of pharmacokinetic data resulting from the application of non-stereospecific analytical methods.