Cytochrome P450 2D6 (CYP2D6), a member of the cytochrome P450 mixed-function oxidase system, is one of the most important enzymes involved in the metabolism of xenobiotics in the body. Also, many substances are bioactivated by CYP2D6 to form their active compounds. There is considerable variability in its expression in the liver. Quantitative real-time polymerase chain reactions (qRT-PCR) have become the method of choice for rapid, sensitive, quantitative comparison of the CYP2D6 copy number variation . A TaqMan real-time PCR assay to specifically amplify genomic CYP2D6 was established by using a specific set of amplification primers and probe, located in exon 9, which effectively prevent amplification of CYP2D7 and CYP2D8 pseudogenes .