ABSTRACT
Foreign compound-induced alterations in drug-metabolizing enzyme activites may cause profound changes in the biological effects of that same compound, of other foreign compounds, and also of endogenous substrates of the same enzymes. Thus, repeated administration of a drug may result in changes in its pharmacokinetics which will alter its efficacy or toxicity. The results of interactions between a drug-metabolizing enzyme-modifying agent and other drugs, pesticides, or environmental chemicals are frequently difficult to predict, because both activation and detoxication pathways are often affected. The consequences of modifying agent-invoked alterations in the metabolism of endogenous substrates are even less well understood, but their potential biological significance must not be ignored. There are three ways in which the activity of drug-metabolizing enzymes may be modified.
