How metabolites may augment some psychostimulant actions of amphetamine

Implications of chirality and geometric isomerism in some psychoactive drugs and their metabolites

Many drugs contain a chiral centre, or such a centre is introduced during metabolism of the drug in man and in animals. If a single chiral centre is present, the drug will normally exist as a mixture of two enantiomers, of which one may have quite different pharmacologic and/or toxic effects than the other. Chiral drugs that are used in psychiatry, and some other pharmacologically related drugs are identified, and the implications of the presence of one or two chiral centres in these drugs are discussed. Differences in pharmacologic properties of drug and metabolite enantiomers are identified and discussed. Also reviewed are the properties of some drugs used in psychiatry that both are chiral and display geometric isomerism.

Metabolic implications of chiral centres in psychotropic drugs

1. Various drugs of neuropsychopharmacological importance contain one or more chiral centres, or centres of asymmetry are introduced during drug metabolism. 2. A drug or drug metabolite with one asymmetric centre exists in two enantiomeric forms, of which usually only one possesses the desired pharmacological activity. The other enantiomer may be inert, or possess an undesired activity. 3. In certain circumstances it is appropriate to administer the racemic drug (mixture of enantiomers), while on other occasions only the pure enantiomer which possesses the desired activity should be given. 4. Drugs employed in psychiatry that contain centres of asymmetry, or are metabolized to pharmacologically active chiral products are identified and implications of chirality are discussed.