Debrisoquine and S-mephenytoin hydroxylation polymorphisms in a Russian population living in Estonia.

Objective: To investigate the CYP2D6 and CYP2C19 phenotypes and genotypes in a Russian population of Estonia.
Methods: Two hundred and eighteen unrelated healthy subjects of Russian origin were studied. All participants took 10 mg debrisoquine and 100 mg S/R-mephenytoin for phenotyping. The CYP2D6 genotype was analysed by PCR amplification for the CYP2D6*3 and CYP2D6*4 alleles and subjects with S/R-mephenytoin ratios of greater than 0.5 were genotyped with respect to CYP2C19*2 and CYP2C19*3 alleles.
Results: Seventeen subjects (7.8%) were classified as poor metabolisers of debrisoquine and 5 (2.3%) as poor metabolisers of S-mephenytoin. The frequency of CYP2D6*4 was 14.4% and that of CYP2D6*3 1.4%. Seven of 15 poor metabolisers of debrisoquine (47%) carried two defective CYP2D6 alleles (CYP2D6*3 or CYP2D6*4). Six of the 10 S-mephenytoin poor-metaboliser alleles (60%) carried either the CYP2C19*2 or CYP2C19*3.
Conclusion: The frequencies of poor metabolisers of debrisoquine and S-mephenytoin among Russians were similar to those in other Caucasian populations. The CYP2D6 poor-metaboliser phenotype was predicted by PCR-based amplification for the CYP2D6*3 and CYP2D6*4 alleles with 47% accuracy. The frequency of the CYP2D6*4 allele was lower in Russians than in other Caucasian populations studied so far.