Double Blind, Placebo-Controlled, Randomised Investigation of Ondansetron in Schizophrenia

Ondansetron is a medication currently approved by the Australian Therapeutic Goods Administration for the treatment of drug-induced vomiting and nausea. Beyond this traditional use there have been several case reports and small clinical trials advocating the use of Ondansetron in the treatment of adult Schizophrenia. Overall these studies lend support to the use of Ondansetron in conjunction with mainstream antipsychotic medication in improving not only the positive symptoms associated with Schizophrenia but also the 'hard to treat' negative and cognitive symptoms. Furthermore, Ondansetron may also have potential benefits in reducing the adverse motor effects (e.g. tremor, uncontrolled muscle movements) associated with the use of many antipsychotic medications. 60 participants aged 18-65 inclusive with a DSM-IV diagnosis of Schizophrenia, Schizoaffective, or Schizophreniform disorder will be recruited. This study proposes to conduct a randomized, controlled treatment trial to investigate the efficacy of ondansetron as an adjunctive treatment in reducing negative and positive symptoms plus improving cognitive symptoms. There will be an initial screening session to determine participant suitability, a baseline session where the study medication (Ondansetron or Placebo) will be dispensed, followed by three monitoring visits. The efficacy of Ondansetron will be evaluated by the following instruments: * Positive and Negative Symptom Scale (PANSS) * Montgomery-Åsberg Depression Rating Scale (MADRS) * C-Reactive protein (marker of systematic and brain specific inflammation) Safety will be assessed through adverse event reporting using the Adverse symptom Checklist (ASC), blood analysis, urinalysis, a 12-lead Electrocardiogram (ECG) and a physical examination. Adverse motor symptoms will also be assessed by the Abnormal Involuntary Movement Scale and the Simpson-Angus Scale. In addition a safety and monitoring committee consisting of research and medical staff external to the project will regularly review adverse events.