Use of candidate gene markers to guide antipsychotic dosage adjustment

To improve antipsychotic treatment in schizophrenia patients, many studies have investigated genetic polymorphisms associated with antipsychotic metabolizing enzymes and receptors. While these studies have typically focused on drug response, few have investigated genetic influences on antipsychotic dosage. This study set out to analyze the association between 134 SNPs in 38 candidate genes and antipsychotic dosage in schizophrenia patients.

For our analysis, 300 patients with a diagnosis of either schizophrenia or schizoaffective disorder were recruited between the ages of 18 and 75. A cross-sectional assessment was used, in which data were collected from each participant through an interview and self-report questionnaire. Antipsychotic dose was standardized according to the chlorpromazine equivalents, defined daily dose and relative to the maximum dose specified in the product monograph. Participants were genotyped using a Customized Illumina Chip comprising 134 SNPs, and all markers were screened for nominal significance.

The analysis showed a nominally significant association with the GFRA1 gene.

The common variants investigated in this study had no major influence on the antipsychotic dosage prescribed in study participants. It remains, though, that this strategy may prove valuable clinically and warrants further investigation.