Substance Use in Schizophrenia: Efficacy of Atypical Antipsychotics

Background: Substance Use Disorders (SUDs) are common among patients with schizophrenia and dramatically worsen their outcome. In the last years, the use of Atypical Antipsychotics (AAPs) in dual diagnosis has become an encouraging clinical strategy. Aim of the present paper is to provide a systematic literature review on efficacy and safety of AAPs use in schizophrenic patients with comorbid SUD. Methods: We searched PubMed to identify original studies pertaining the use of AAPs in treating dual-diagnosed schizophrenic patients. Results: We found 12 papers that met our inclusion/exclusion criteria: five randomized clinical trials, two open label trials and five observational studies. 1432 schizophrenic patients, 905 of them with a comorbid SUD, were involved. Olanzapine, Risperidone and Clozapine were the most prescribed AAPs; alcohol, cannabis and cocaine the most frequent substances of abuse. None of the selected studies was placebo-controlled: AAPs were compared to Typical Antipsychotics (TAPs) or one another. AAPs resulted usually, but not always, more efficacious than TAPs on substance related problems. In those studies comparing different AAPs, clozapine showed better results than other treatments, whereas no significant differences emerged between risperidone and olanzapine. In terms of safety, AAPs were usually well tolerated. Conclusions: Our review suggests that AAPs, in particular clozapine, olanzapine and risperidone, may be a promising therapeutic option for schizophrenic patients with comorbid SUD. On the other hand, given the limited number of randomized controlled trials and the lack of placebo arms, further studies are needed to better address this point.