摘要: The human genome comprises 57 putatively functional, protein-coding cytochrome P450 (CYP) genes that are grouped according to their sequence similarity into 18 families and 44 subfamilies. Approximately one dozen CYP isozymes of 1, 2, 3 mainly responsible for the metabolism drugs other xenobiotics. Large interindividual variability these enzymes, which both genetic nongenetic factors contribute, is an important determinant drug pharmacokinetics response. This chapter summarizes clinical, toxicological relevance polymorphism, affects all drug-metabolizing CYPs, but a very different extent. Keywords: cytochrome P450; drug metabolism; pharmacogenetics; pharmacogenomics; polymorphism