Efficacy, acceptability and tolerability of antipsychotics in patients with schizophrenia and comorbid substance use. A systematic review and meta-analysis

Patients with schizophrenia and substance related comorbidity or substance induced psychotic disorder are difficult to treat. Although the prevalence of a comorbid substance use is approximately 40% in schizophrenia, such patients are usually excluded from clinical trials. We therefore performed a random-effects meta-analysis of all randomized controlled antipsychotic drug trials in this patient subgroup. We searched multiple databases up to May, 2018. The primary outcome was the reduction of substance user; secondary outcomes were craving, mean reduction of substance use, overall change in schizophrenia symptoms, positive and negative symptoms, response, dropouts, quality of life, social functioning, weight gain, sedation, prolactin, extrapyramidal side effects and use of antiparkinsonian medication. We identified 27 references from 19 RCTs published from 1999 to March 2017 including 1742 participants. The most frequent types of substance abuse were cannabis (8 studies) and cocaine (6 studies) use/dependence. Clozapine was superior to other antipsychotics for reduction of substance use and risperidone to olanzapine for craving. Olanzapine, clozapine and risperidone showed superiority for symptom reduction compared to some other drugs. When reported, results of side-effects followed known patterns. The evidence-base is considerable (19 RCTs), however, firm conclusions cannot be drawn due to small sample sizes of individual studies and insufficient reporting.