Despite decades of study, the etiology and physiopathology of schizophrenia remain unknown. Recent evidence suggests that nitric oxide (NO) may be implicated in schizophrenia. NO is a gas that mediates the release of neurotransmitters, learning, memory, and neurodevelopment. Studies investigating the role of NO in patients with schizophrenia found evidence that points to a disruption in NO-mediated neurotransmission. Therefore, we investigated the effects of sodium nitroprusside, a NO donor, as an add- on treatment for patients with schizophrenia.