Introduction: Patients with schizophrenia characteristically exhibit cognitive deficits. The level of cognitive impairment is found to predict the functional outcome of the illness more strongly than the severity of positive or negative symptoms. The purpose of this study was to assess the efficacy of ondansetron, a 5-HT3 receptor antagonist as an adjuvant agent in the treatment of chronic schizophrenia in particular for cognitive impairments.

Methods: This investigation was a 12-week, double blind study of parallel groups of patients with stable chronic schizophrenia. Thirty patients were recruited from inpatient and outpatient departments. All participants met Diagnostic and Statistical Manual of Mental Disorders Fourth Edition, Text Revision (DSM-IV-TR) criteria for schizophrenia. To be eligible, patients were required to have been treated with a stable dose of risperidone as their primary antipsychotic treatment for a minimum period of 8 weeks. The subjects were randomized to receive ondansetron (8 mg/day) or the placebo in addition to risperidone. Cognition was measured by a cognitive battery. Patients were assessed at baseline and after 8, and 12 weeks after the medication started.

Results: Administration of ondansetron significantly improved visual memory based on improvement on visual reproduction, visual paired associate and figural memory sub tests of Wechsler Memory Scale Revised.

Discussion: The present study indicates ondansetron as potential adjunctive treatment strategy for chronic schizophrenia particularly for cognitive impairments.