Schizophrenia is treated with antipsychotics and other psychotropic medications, many of which are substrates for the highly polymorphic CYP2D6 enzyme. The most frequent variant allele is CYP2D6*4- leading cause of poor metabolism (PM) phenotype. PM causes the reduction of therapeutic response, increase the risk of adverse drug reactions and increase the plasma concentration of both drug and its metabolites above the levels of toxicity.

Analysing CYP2D6*4 allele frequency among schizophrenic patients for further individualisation and rationalisation of therapy.

Research was conducted on 38 schizophrenic patients and 110 healthy individuals. CYP2D6*4 allele was detected with allele specific PCR.

Both wild type allele carriers are 55% of the schizophrenic patients, 45% are wild type/*4heterozygous, and *4/*4 homozygous are not identified. There is a statistically significant difference in the genotype distribution (P < 0.05) between schizophrenic patients and healthy individuals. Significantly higher *4 allele frequency (37%) comparing to healthy individuals (P < 0.0001) indicates the necessary caution in administration of CYP2D6 substrates. A lower frequency of PMs in schizophrenic patients than in healthy individuals could be explained with CYP2D6 neuroactive substrate metabolism. Forty-five percent of the schizophrenic patients are intermediate metabolisers carrying the higher risk of adverse response to CYP2D6 substrates comparing to wild type homozygous. As none of the analyzed patients was PM, exceeded plasma concentrations of medications above toxic levels are not expected when administrating the right dosage.

Altered CYP2D6 metabolism may contribute to the vulnerability, clinical severity and treatment outcome of schizophrenia.

The authors have not supplied their declaration of competing interest.