No influence of SLC6A3 40 base VNTR polymorphism on the response to risperidone.

Abstract Objectives. The SLC6A3 40 base variable number of tandem repeats (VNTR) polymorphism has been associated with several clinical phenotypes associated with dysregulation of dopamine transmission. However, there is only little evidence about a possible influence of such genetic variant on the response to antipsychotics. The aim of the present study is to investigate whether SLC6A3 40 base VNTR polymorphism could modulate response to risperidone in a sample of Korean schizophrenia subjects. Methods. One hundred and forty-two schizophrenia inpatients were treated with a flexible dose of risperidone. Efficacy was assessed at baseline and at discharge using the scores of the Clinical Global Impression-severity (CGI-S), Brief Psychiatric Rating Scale (BPRS) and Positive and Negative Symptom Score (PANSS). Multivariate analysis of covariance was used to test possible influences of SLC6A3 VNTR variants on clinical scores. Results. None of the genotypes and of the alleles under investigation was associated with clinical scores at discharge or with changes of clinical scores over time. In addition, we also failed to find any association between genotypes and allele frequency distribution in accordance with treatment response defined as a 20% (or 30%) or more reduction in the total PANSS scores from the baseline to the end of treatment. Conclusion. Our findings do not suggest a possible association between SLC6A3 40 base VNTR polymorphism and response to risperidone. However, because of several limitations including the investigation of a single drug, the flexible design of the present study and the absence of a complete coverage of features which could influence the response, further investigations could be required.