Introduction: Given the role of opioids and their antagonists on dopamine secretion, the effect of naltrexone use in the treatment of schizophrenia was evaluated in this study.

Method: In a double blind placebo controlled clinical trial study on a group of 34 patients with schizophrenia on maintenance therapy with antipsychotics, 17 patients received naltrexone (50 mg, BID) and 17 patients received placebo (BID). The patients were evaluated at the start of the trial, as well as three and six weeks after, using Positive and Negative Syndrome Scale (PANSS).

Results: Patients receiving naltrexone showed improvement in positive symptoms from week three to week six, and improvement in negative symptoms from week one to week three.

Conclusion: Naltrexone had no significant effect on positive or negative symptoms of schizo-phrenia compared to placebo.