5. Chirality and pharmacokinetics

As a general rule, whether we're talking about a racemate, a pure enantiomer or a non-chiral drug, knowledge of pharmacokinetic parameters is essential before any drug can be marketed. Pharmacokinetics enable us to determine absorption rates, binding to plasma proteins, distribution to various tissues, metabolism with or without the formation of one or more metabolites, elimination and half-life, all of which help define the drug's mode of use.

Moreover, since amino acids, carbohydrates, complex lipids and macromolecules in living matter such as plasma proteins, enzymes, membrane and nuclear receptors are asymmetric, interactions with chiral molecules can be enantioselective, leading to different pharmacokinetic parameters for each enantiomer. The same applies to the action of enzymes, which may act differently on each enantiomer, leading to the formation of different...