The role of the poor metabolizer genotype CYP2D6 and CYP1A2 phenotype in the pharmacokinetics of duloxetine and venlafaxine - a case report.

: Cytochrome P450 (CYP) isoenzymes mediate the oxidative metabolism of most psychotropic drugs. Genetic polymorphisms of some isoenzymes such as CYP2B6, 2C19 or 2D6 affect drug metabolism due to changes in enzymatic activity. The CYP2D6 gene is localized on chromosome 22 with more than 46 known different major polymorphic alleles to date. The variant CYP2D6 alleles can be classified into categories, which cause abolished, decreased, normal, increased or qualitatively altered catalytic activity [1]. Accordingly, the polymorphism of the enzyme results in poor, intermediate, extensive or ultrarapid metabolizers of CYP2D6 drugs. The CYP2C19 gene, located on chromosome 10, is also highly polymorphic exhibiting 47 currently known star alleles.