Most drugs are at least partly metabolized by the cytochrome P450 (CYP) system, a family of enzymes that seems to have evolved to help cope with environmental toxins. Variation in the genes encoding the cytochrome enzymes is extensive, and has long been known to affect metabolism of certain drugs, including psychotropics like olanzepine, sertraline, and several benzodiazepines. For these reasons, the CYP genes have been extensively studied in psychiatry and a gene-chip that captures most of the relevant functional variation is being promoted for use in the field [for review, see Black et al 2007]. So far, however, the clinical utility of such testing has not been proven for most patients [EGAPP Working Group, 2007]
