Distribution of polymorphism in the Middle Eastern region.

Cytochrome P450 2D6 (CYP2D6) is an important drug-metabolizing enzyme involved in the pharmacokinetic metabolism of drugs. gene is highly polymorphic, and the combination of its different alleles yields different phenotypes including extensive metabolizer (EM), intermediate metabolizer (IM), poor metabolizer (PM), and ultrarapid metabolizer (UM). Genotyping of the important alleles for this gene in different ethnicities is of particular importance for assessing the efficacy of various drugs. In this study, we reviewed the allele and phenotype frequencies predicted from the genotypes of in the Middle East area. Regardless of different ethnicities, the *41 allele frequency was shown to be higher than that of other reduced functional alleles. In addition, *4 was the most frequent nonfunctional allele in all studied populations in the Middle East. Taken together, our findings illustrated that the frequencies of PM or IM alleles and different genotypes harboring these alleles are relatively high in the Middle Eastern countries. Therefore, the study of alleles for each patient to detect those that are at risk is of great importance to prevent adverse drug reactions through individualization therapy.