Background: CYP2D6 is responsible for the metabolism of approximately 25% of all drugs. The expression of cytochrome P450 2D6 (CYP2D6) is influenced by a combination of factors including polymorphisms in the CYP2D6 gene. Analysis of the CYP2D6 genotype is used to personalize the medication to a patient's metabolism. Although many genotypes can be determined using standard genotype analysis, in some cases, an incomplete analysis is performed. The CYP2D6 genotype *1/*4 often occurs in combination with a multiplication of the CYP2D6 gene, and is reported as (*1/*4)xN. Accurate determination of the multiplied gene is essential to provide a phenotype prediction for these patients. Duplication of the *1 gene leads to an extensive metabolizer genotype whereas multiplication of the *4 gene would not lead to extra functional enzyme and therefore provides an intermediate metabolizer phenotype.
Methods: Here, a technique is described in which the copy numbers of both the *4 and *1 genes are determined using quantitative PCR techniques.
Results and conclusions: This technique provides a method to predict the patient's CYP2D6 phenotype, and is therefore an important step toward personalized medicine.
Keywords: CYP2D6; copy number variations (CNV); pharmacogenetics; ultrarapid metabolizer.