Background: Personalized approach is one of the options to overcome treatment
failure in psychiatry and increase the efficacy of antipsychotic treatment for an individual
patient by using genetic tests.
Objective: The aim of this study was to investigate the frequency of MDR1 (C3435T),
CYP2D6, CYP2C19, and CYP1A2 genotypes in psychiatric patients with treatment failure
to antipsychotics to compare the results with those published for the Russian population.
Methods: A total number of 52 patients attending a psychiatry outpatient clinic were included
in the study. All patients required changing the therapy with antipsychotics due to
Results: We revealed the higher frequency of Т/Т MDR1 (C3435T) homozygotes among
study patients as compared with the Russian healthy population. For CYP1A2, the higher
frequency of normal metabolizers (*1A/*1A) and lower frequency of slow metabolizers
(*1F/*1F) were observed. No difference was found for intermediate metabolizers
(*1A/*1F) and one patient had *1A/*1C genotype with decreased activity. For the majority
of CYP2D6 genotypes, the observed frequencies were similar to those reported for the
Russian healthy population except for CYP2D6 *3/*4 (slow metabolizers), for which
higher frequency among study patients was found. The frequencies of CYP2С19 genotypes
were comparable to the Russian population, however, no slow metabolizers (*2/*2,
*2/*3, *3/*3 genotypes) were identified.
Conclusion: Psychiatric patients with treatment failure to antipsychotics demonstrated a
high frequency of T/T MDR1 (C3435T) and CYP2D6 *3/*4 genotypes coding inactive
proteins. The frequency of CYP1A2 wild type genotype *A/*A was higher with a simultaneous
decrease in the frequency of *F/*F genotype compared with the healthy Russian
population. Further studies of MDR1 (C3435T) genotype as well as CYP2D6, CYP2C19,
and CYP1A2 genotypes frequency should be conducted in patients with treatment failure