Risperidone-Induced Adverse Drug Reactions and Role of DRD2 (–141 C Ins/Del) and 5HTR2C (–759 C>T) Genetic Polymorphisms in Patients with Schizophrenia

OBJECTIVE: To determine the adverse drug reaction (ADR) profile of risperidone and their association with dopamine (DRD2 − 141 C Ins/Del/rs1799732) and serotonin receptor (5HTR2C −759 C>T/rs3813929) gene polymorphisms in patients with schizophrenia. MATERIALS AND METHODS: The study was conducted among 289 patients who were diagnosed with schizophrenia and were on treatment with risperidone (4–8 mg/day)-based therapy for a minimum of 4 weeks. Genotyping was carried by real-time quantitative polymerase chain reaction. All the patients were observed for the occurrences of ADRs during the study. Changes in prolactin levels and body weight were analyzed for a subgroup of 102 and 97 patients, respectively. RESULTS: Risperidone-induced extrapyramidal symptoms (EPSs) were seen in 36.7% of patients. Among them, tremors were the most common symptom 31.8%. Risperidone-induced hyperprolactinemia and weight gain were seen in 87.2% and 53.6% in subgroup patients. Adverse effects such as sedation, gastrointestinal effects, and amenorrhea were seen in 9.7% (28/289), 5.1% (15/289), and 6.1% (7/114), respectively. Occurrence of DRD2 − 141 Ins/Del and Del/Del polymorphisms were significantly associated with increased prolactin levels in response to risperidone (odds ratio [OR] = 10.45; 95% confidence interval = 1.29–84.89, P = 0.004). No such association was observed with 5HTR2C (−759 C>T) polymorphism. Weight gain and EPS were not associated with the above genetic polymorphisms. CONCLUSION: Hyperprolactinemia, weight gain, and EPSs (>36.7%) were common adverse effects of risperidone. DRD2 – 141C Ins/Del and Del/Del polymorphisms were significantly associated with increased prolactin levels (OR = 10.45) in response to risperidone.