Clozapine-induced weight gain associated with the 5HT2C receptor -759C/T polymorphism

Weight gain has been documented as a significant adverse effect associated with many of the atypical antipsychotic medications. Several recent reports have linked a -759C/T polymorphism of the 5HT2C receptor gene and obesity as well as chlorpromazine, risperidone, and clozapine induced to weight gain. This aim was to determine the association between changes in body mass index (BMI) during clozapine treatment and the -759C/ T polymorphism of the 5HT2C receptor gene. This study included 41 patients with treatment-refractory schizophrenia (DSM-IV) who were followed prospectively during treatment with clozapine. Weight and height measurements were obtained prior to starting clozapine and after 6-months of treatment. Genomic DNA was isolated from a whole blood sample and analyzed for the -759C/ T polymorphism of the 5HT2C receptor gene. A χ² analysis comparing whether or not the subjects carried a -759T allele in subjects grouped as having an increase of more or less than 7% of their baseline BMI during treatment with clozapine found that the presence of the -759T allele was significantly higher in subjects with less than or equal to a 7% increase in baseline BMI compared to those with a greater than 7% increase in BMI. A multiple linear regression analysis showed that both baseline BMI and the presence or absence of the -759T allele had significant effects on 6-month BMI. The T allele may have a protective function in preventing significant weight gain from clozapine. Subjects without the -759T variant allele were at a greater risk for weight gain from clozapine over 6-months compared to those with the -759T allele.