The gene CYP2D6 is of great interest also due to its highly polymorphic nature, and involvement in a high number of medication metabolisms. The presence of polymorphisms in the CYP2D6 gene may modulate enzyme level and activity, thereby affecting individual responses to pharmacological treatment.

Allele and genotype frequency distributions of CYP2D6*10 variants and predicted phenotypes were analyzed in blood samples of 123 patients (53 patients from north-western region and 69 patients from Siberian region) using polymerase chain reaction (PCR)-restriction fragment length polymorphism, PCR-single-strand conformation polymorphism.

The T/T, C/T, and C/C genotype frequencies of the CYP2D6*10 allele were significantly different (P < 0.01) in regional groups. The frequency of the wild homozygous variant C/C of the CYP2D6*10 allele (extensive metabolizers) in the Siberian region was the highest, while the north-western region of Russia had the lowest frequency (P < 0.001), which are 82.6% and 64.2%, respectively. The frequency of the heterozygous variant C/T of the CYP2D6*10 allele (intermediate metabolizers) was significantly a bit high in the north-western region, while the Siberian region of Russia had the lowest frequency (P < 0.001), which are 35.8% and 17.4%, respectively. The homozygous variant T/T of theCYP2D6*10 allele (poor metabolizers) was not identified.

The C100T polymorphism of the CYP2D6 gene may be associated with several drug-induced reactions in patients with depression, schizophrenia, epilepsy etc. The differences in the prevalence of intermediate metabolizers in north-western and Siberian regions of Russia may be due to genetic drift and accumulation of alleles typical of European and Asian populations.

The authors have not supplied their declaration of competing interest.