A BRIEF REVIEW OF SCIENTIFIC AND REGULATORY CONSIDERATIONS

Stereoisomers are molecules that are identical to one another in terms of atomic constitu-tion and sequence of covalent bonds, but which differ in the three dimensional arrangement of atoms. There is a growing belief that enantioselectivity in the pharmacodynamic and pharmacokinetic properties of a drug is not a rare phenomenon, but occurs rather frequently. Because of differences in pharmacological activity between enantiomers, race-mic mixtures can, in theory, be seen as combination products. Recognition of potential differences of pharmaceutical enantiomers has led to increasing attention by regulatory agencies to developments with such compounds. This paper will briefly review the scien-tific and regulatory guidance provided for the development and approval of chiral drugs in Canada, and relate this to the requirements currently in place in the United States and Europe. Key Words: Chiral; Pharmaceuticals; Guidelines; Regulatory; Stereoisomers INTRODUCTION For a molecule with n chiral centers, there may be up to 2n stereoisomers. Within stereo-STEREOISOMERS ARE MOLECULES isomer classification, there are molecules that are identical to one another in terms o