Pharmacogenomic genotyping methodologies.

"Personalized medicine" based on an individual's genetic makeup is slowly becoming a reality as pharmacogenomics moves from the research setting to the clinical laboratory. Concordance studies between genotype and phenotype have shown that inherited mutations in several key drug-metabolizing enzymes, such as cytochrome P450 ( CYP ) 2D6 , 2C9 , and 2C19 , result in several distinct phenotypes that lead to different individual responses following drug administration. One of the major driving forces behind pharmacogenomics and its ability to be used effectively are the technologies that are available. A beneficial genotyping test must identify most or all of the mutations that have a significant impact on the expression or function of drug-metabolizing enzymes, transporter proteins, and/or drug receptors. Selection of the appropriate technology will be based on several issues, including prior knowledge of the mutation/polymorphism, sensitivity/specificity, sample requirements, and cost. Since the future volume of pharmacogenomic testing is anticipated to be large, automation of pharmacogenomics will also become increasingly important. This paper provides an overview of current technologies available for assessing polymorphisms on a small- to large-scale basis.

Pharmacogenomics as molecular autopsy for postmortem forensic toxicology: genotyping cytochrome P450 2D6 for oxycodone cases.

Pharmacogenomics, the study of the impact of heritable traits on pharmacology and toxicology, may serve as an adjunct for certifying opioid fatalities. Oxycodone, frequently prescribed for the relief of moderate to severe pain, is metabolized by cytochrome P450 (CYP) 2D6, encoded by a polymorphic gene with three mutations (*3, *4, and *5) with a combined 95% allelic frequency and about 10% prevalence. Individuals with variant alleles are more susceptible to oxycodone toxicity. By assessing the prevalence of CYP2D6 polymorphisms and covariables, we hypothesized that oxycodone fatality may be partially due to poor drug metabolism caused by CYP2D6 variant alleles. From the Milwaukee County Medical Examiner's Office (MCMEO), a retrospective analysis of 15 oxycodone cases was followed by genotyping blood samples for the variant alleles by conventional and real-time PCRs. Institutional Review Board approval was obtained. Oxycodone, extracted from blood and/or urine, was quantitated by GC-MS. The results show two homozygous for 2D6*4 and four heterozygous for 2D6*4. The MCMEO was not significantly different from those in the control group (n = 26) (p > 0.05, Fisher's Exact Test). However, genotyping CYP2D6 provided a more definitive interpretation of the oxycodone toxicity in four cases. Therefore, pharmacogenomics may serve as an adjunct in the determination of the cause and manner of death in forensic toxicology and a pharmacogenomic algorithm for genotyping has been proposed.