Systematic Literature Review of Quetiapine for the Treatment of Psychosis in Patients With Parkinsonism.

Objective: The purpose of this article was to determine the efficacy and tolerability of quetiapine compared with placebo or other interventions for psychosis in parkinsonism.

Methods: Participants with a diagnosis of parkinsonism participated in randomized controlled trials (RCTs) investigating the efficacy and tolerability of quetiapine for psychotic symptoms within a defined follow-up period. The authors conducted searches on PubMed, Cochrane Controlled Register of Trials, and EMBASE for articles published from January 1991 to October 2017. Study methodology and patient- and treatment-level data were independently extracted and summarized by using descriptive statistics. Studies underwent quality assessment for risk of bias.

Results: A total of 17,615 unique records were identified, and seven RCTs (total N=241) met inclusion criteria. Five RCTs were placebo controlled, and two compared quetiapine against clozapine. The mean study duration was 12 weeks, and the mean daily quetiapine dose was 103 mg per day (range, 12.5-300 mg). In four of five placebo-controlled RCTs, quetiapine failed to demonstrate significant improvement of psychosis in parkinsonism compared with placebo. In two clozapine-comparator RCTs, quetiapine was better tolerated but no more effective than clozapine. Across all RCTs, the mean completion rates for quetiapine, clozapine, and placebo were 66%, 68.5%, and 66%, respectively. Quetiapine did not significantly worsen motor function.

Conclusions: The efficacy of quetiapine in RCTs for psychosis in parkinsonism is no better than that for placebo or clozapine. On the basis of novel data, clinicians should reevaluate traditional viewpoints on the benefits of quetiapine for psychosis in parkinsonism.