Physical Properties and Crystal Structures of Chiral Drugs

Abstract

More than half of all marketed drugs contain one or more chiral centers and are therefore members of the category of chiral drugs (Millership and Fitzpatrick 1993). Because the biochemical processes of life are either stereospecific or stereoselective, opposite enantiomers and racemates of chiral drugs may differ markedly in the following properties: pharmacological (Islam 1997), toxicological (Wainer 1993), pharmacodynamic and pharmacokinetic (Drayer 1986; Midha et al. 1998). Some chiral drugs must therefore be marketed as pure enantiomers from both the practical and regulatory points of view (Pifferi and Perucca 1995; Testa and Trager 1990). However, from a commercial viewpoint, racemates can usually be manufactured more economically than enantiomers; hence, many chiral drugs are still marketed as racemates. However, a recent trend is towards marketing more singleenantiomer drugs (Stinson 1998).