Pharmacogenomic testing provides an innovative strategy to improve the likelihood of selecting an effective psychotropic medication. The earliest medical texts recognize that individual patients experience quite dramatically different responses to the same drug. There is also a longstanding observation that unusual drug responses can occur in members of the same family. The identification of specific gene variants associated with idiosyncratic responses is about 50 years old,3 and the recognition that some psychiatric patients metabolize Inhibitors,research,lifescience,medical antidepressants at dramatically different rates has been documented for several decades.4 However, with the use of newer antidepressant medications that rarely

have life-threatening complications, the relatively expensive practice of monitoring the serum levels of newer antidepressant medications has become uncommon in the United States. This change has occurred despite the fact that serum levels of these newer agents also have dramatic variations based on the metabolic capacity of each patient. Inhibitors,research,lifescience,medical A decade ago, the cost of genotyping began to become more affordable, and individual laboratories initiated pharmacogenomic testing that would provide genotyping of individual

cytochrome P450 genes. However, there was no standard or well-validated methodology for the genotyping of these informative genes. There was also Inhibitors,research,lifescience,medical considerable variability in the interpretation of the results. In 2004, the US Food and Drug Administration (FDA) approved the use of a new product, the AmpliChip.5 The introduction of the AmpliChip

provided reference laboratories with a standard method for identifying variations in two of the cytochrome P450 genes: cytochrome P450 Inhibitors,research,lifescience,medical 2D6 (CYP2D6) and cytochrome P450 2C19 (CYP2C19). The approval of the AmpliChip was an important landmark in the history of psychiatric pharmacogenomic testing, and within 3 years, CYP2D6 and CYP2C19 were being genotyped by every reference laboratory in the country. However, this advance also highlighted some of the challenges associated Inhibitors,research,lifescience,medical with the introduction of clinical testing. One of the most obvious challenges that must be addressed is how to begin to assess new variants of these two genes in beta-catenin activation updated versions of the assay. Ideally, the methodology for establishing drug-metabolizing phenotypes should be updated Metalloexopeptidase regularly based on new molecular genetic findings showing how new genotypic variants influence gene function. Also, the clarification of the predictive capacity of previously identified gene variants influencing gene function is similarly evolving, and newly identified associations between gene structure and function should ideally be incorporated into algorithms that define the metabolic capacity of psychiatric patients. The evolution of pharmacogenomic research should inform modifications in pharmacogenomic testing.