Evaluation of cytochrome P450 enzymes in drug interactions

Cytochrome P450 (CYP) enzyme is a super family of the Phase I enzymes in the biotransformation of xenobiotics. Most drugs undergo deactivation by CYP, either directly or by facilitated excretion from the body. In addition, CYP plays a primary role in drug interactions that can result in drug toxicity, reduced pharmacological effect, and adverse drug reactions. At the same time, many drugs also have the ability to affect CYP expression and activity that may have the potential to interfere with drug metabolism. Although the clinical importance of drug interactions depends on many factors associated with the particular drug and patient, recognizing whether the drug involved acts as a CYP enzyme substrate, inducer, or inhibitor can prevent clinically significant interactions from occurring. This chapter briefly reviews the mechanisms for drug interactions, problems in monitoring drug interactions, methods to assess drug interactions, and the role of CYP enzymes in drug interactions. A better understanding of interactions of drugs with CYP will help the regulation of the use of drugs, avoid co-administration or anticipating potential problems, and adjust a patient's drug dose early in order to provide optimal response with minimal adverse effects.