Efficacy of Quetiapine in the Treatment of Patients With Schizophrenia and a Comorbid Substance Use Disorder

Comorbid alcohol/substance use disorder (SUD) in schizophrenia is a major concern, both in view of the high frequency of SUD among patients with schizophrenia and the difficulty in managing such patients. Though antipsychotic medications are effective in reducing symptoms and impairment in persons with schizophrenia, the typical antipsychotic agents are of limited value in controlling alcohol/substance use in these patients. Extrapyramidal, dysphoric side effects of conventional neuroleptics may actually promote the use of substances in an attempt to counteract these effects. Novel antipsychotics have radically altered treatment expectations and outcomes for patients with severe forms of schizophrenia. With the greater availability of novel agents in clinical practice, it has been noted that these benefits have also extended to specific subgroups of patients including patients with comorbid SUD. Several retrospective studies have demonstrated a decrease in comorbid substance use in patients with schizophrenia treated with clozapine. There is little data available, however, on the efficacy of quetiapine in patients with schizophrenia and comorbid SUD. Its receptor profile, including a weak Dopamine2 (D2) receptor blocking ability and substantial effects at noradrenergic receptors, makes it a logical antipsychotic to use in the comorbid population. The study is an open-label investigation of the efficacy of quetiapine in a group of 30 patients with schizophrenia and comorbid substance use disorder. Patients diagnosed with schizophrenia or schizoaffective disorder and a comorbid substance use disorder are switched to quetiapine for 12 weeks. We hypothesize that quetiapine treatment will be associated with a decrease in substance use. Moreover, we further hypothesize that measures of symptoms, cognition and quality of life will also improve over baseline assessments in patients treated with quetiapine. Data suggesting a beneficial effect of quetiapine will have to be confirmed in a prospective double-blind study. This pilot investigation will provide preliminary data and effect sizes that will be used in the design of this subsequent investigation.