Functional consequences of polymorphism of xenobiotic metabolising enzymes.

There are important interindividual differences in the rate of drug metabolism caused by genetic, environmental, pathological and dietary factors. The genetic variability caused by polymorphism encompasses a large proportion of phase I and phase II enzymes and results in either defect, ultrarapid, partially deficient or qualitatively altered drug metabolism. In this overview the most important polymorphic enzymes are discussed and their consequences for drug metabolism, effective drug treatment and adverse effects of drugs are emphasised.