Chlorpromazine versus metiapine for schizophrenia.

Background: Chlorpromazine, a widely available and inexpensive antipsychotic drug, is considered the benchmark treatment for schizophrenia worldwide. Metiapine, a dibenzothiazepine derivative, has been reported to have potent antipsychotic characteristics. However, no evidence currently exists on the effectiveness of chlorpromazine in treatment of people with schizophrenia compared to metiapine, a newer antipsychotic.

Objectives: To compare the effect of chlorpromazine versus metiapine for the treatment of people with schizophrenia SEARCH METHODS: We searched the Cochrane Schizophrenia Group's Study-Based Register of Trials in November 2015 and 2016.

Selection Criteria: All randomised controlled trials (RCTs) focusing on chlorpromazine versus metiapine for adults with schizophrenia. We included trials meeting our selection criteria and reporting useable data.

Data Collection And Analysis: We extracted data independently. For binary outcomes, we calculated risk ratio (RR) and its 95% confidence interval (CI), on an intention-to-treat basis. For continuous data, we estimated the mean difference between groups and its 95% CI. We employed a random-effects model for analyses. We assessed risk of bias for included studies and created 'Summary of findings' tables using GRADE.

Main Results: We included three studies randomising 161 people with schizophrenia. Data were available for only two of our seven prestated main outcomes. Clinically important improvement in global state was measured using the Clinical Global Impression (CGI). There was no clear difference between chlorpromazine and metiapine groups (2 RCTs, n = 120, RR 1.11, 95% CI 0.84 to 1.47, very low quality evidence) and numbers of participants with parkinsonism at eight weeks were similar (2 RCTs, n = 70, RR 0.97, 95% CI 0.46 to 2.03, very low quality evidence). There were no useable data available for the other key outcomes of clinically important improvement in mental state, readmission due to relapse, satisfaction with treatment, aggressive or violent behaviour, or cost of care.

Authors' Conclusions: Chlorpromazine has been the mainstay treatment for schizophrenia for decades, yet available evidence comparing this drug to metiapine fails to provide high-quality trial based data. However, the need to determine whether metiapine is more or less effective than chlorpromazine seems to be lacking in clinical relevance and future research on this comparison seems unlikely.