Principles of Drug Metabolism, with an Emphasis on Psychiatric Drugs

A knowledge of how drugs are metabolized in the body is often of clinical relevance because often an administered drug is not soley responsible for observed pharmacological and toxicological effects. Regrettably, the formation of drug metabolites is often not considered in pharmacological evaluations, the assumption being that it is the drug itself that is the active species. In many instances, desirable and undesirable drug effects can be correlated with rates of biotransformations and the properties of metabolites; pharmacokinetic drug-drug interactions may also occur if a patient is receiving two or more drugs that compete for the same metabolic enzymes. In the present chapter, we will concentrate on metabolism of drugs used to treat psychiatric disorders, although the principles and protocols discussed are applicable to other classes of drugs as well.