Cytochrome P450 isoenzymes - Importance for the internist

The studies with CYP isoenzymes give hope that in the near future it will be possible to predict the clinical pharmacokinetics of-drugs, if their oxidation can be assigned to the activity of one or well-characterized CYP isoenyzmes (or if metabolism is catalyzed by other well-studied enzymes). This strategy will reduce animal experimentation. Interindividual variability in drug metabolism translates into variability in drug efficacy and toxicity. Establishing the status of-drug-metabolizing enzymes will therefore assist in making predictions of pharmacologic and toxicologic responses to drugs. Many clinically relevant drug-drug interactions can now be readily rationalized in terms of the substrate and inhibitor specificities of individual human CYP isoenzymes. The next 5 years should reveal whether selective inhibitors of xenobiotic-metabolizing CYP's can be used therapeutically in the treatment or prevention of cancer and various endocrine disorders, in analogy to the use of influencing steroidogenic CYP's.