Quetiapine and clozapine in parkinsonian patients with dopaminergic psychosis

Objective: This study aimed to compare the efficacy and safety of quetiapine and clozapine in parkinsonian patients with dopaminergic psychosis in a randomized, open-label, blinded-rater, parallel group trial. Methods: Forty-five patients with Parkinson disease (PD) and psychosis induced by antiparkinsonian drugs were randomly assigned to receive either quetiapine or clozapine. The duration of the trial was 12 weeks. Forty patients, 20 in each treatment group, completed the study. The final dose of quetiapine (mean ± SD) was 91 ± 47 mg/d and that of clozapine 26 ± 12 mg/d. The severity of psychosis was assessed using the Brief Psychiatric Rating Scale (BPRS) and the Clinical Global Impression Scale–Severity Subscale (CGI-S). The Unified Parkinson’s Disease Rating Scale (UPDRS) III was used to assess motor conditions during the study period. The Abnormal Involuntary Movement Scale (AIMS) was performed to evaluate dyskinesias. Results: Forty patients, 20 on clozapine and 20 on quetiapine, completed the study. The psychopathologic state improved significantly (P < 0.001) from baseline in both treatment groups. No differences were found between clozapine and quetiapine at any assessment time. Motor conditions remained unchanged after clozapine and quetiapine. Dyskinesias decreased significantly (P < 0.05) in both groups. Side effects were mild, generally transient, and well tolerated. Conclusions: Quetiapine and clozapine appear equally efficacious for treatment of dopaminergic psychosis in patients with PD.