Randomized controlled trial of aripiprazole versus risperidone for the treatment of amphetamine-induced psychosis

Background: Lifetime prevalence of amphetamine-induced psychotic disorder is reported as being up to 23% for methamphetamine (MA) abusers. Approximately 25% of those with a baseline DSM-IV diagnosis of substance-induced psychosis are diagnosed with primary psychosis at one-year follow-up. Evidence on the treatment of amphetamine psychosis is very limited. Objectives: To investigate the efficacy of risperidone versus aripiprazole in treatment of amphetamine-induced psychotic symptoms. Methods: In a double-blind study, 45 participants were randomly allocated to either aripiprazole 15 mg or risperidone 4 mg daily over a six-week trial. Positive and negative symptoms of psychosis were assessed using the Scale for Assessment of Negative Symptoms (SANS) and the Scale for Assessment of Positive Symptoms (SAPS) at baseline and completion of the trial. Results: SANS and SAPS scores decreased significantly in both groups. Mean SAPS score reduction in risperidone and aripiprazole group was 16.20 and 10.80, respectively, after trial course (p < 0.001). Mean SANS score reduction in risperidone and aripiprazole group was 9.35 and 11.25, respectively (p = 0.08). Conclusions: Both aripiprazole and risperidone were effective for patients diagnosed with amphetamine-induced psychotic disorder. However, risperidone had the greater effect on positive psychotic symptoms while patients with negative symptoms may respond better to aripiprazole. There is a case for further studies evaluating the efficacy of atypical antipsychotics in this disorder.