Quetiapine versus clozapine: a preliminary report of comparative effects on dopaminergic psychosis in patients with Parkinson's disease

This study investigated the efficacy and safety of quetiapine versus clozapine in parkinsonian patients with dopaminergic psychosis. All patients fulfilling the inclusion criteria were randomly assigned to receive either quetiapine or clozapine. The duration of the trial was 12 weeks. The severity of psychosis was assessed using the BPRS and the Clinical Global Impression Scale-Severity subscale (CGI-S). The UPDRS III was used to monitor the progression of PD during the study period. Twenty patients, 10 on clozapine, and 10 on quetiapine, completed the study. The psychopathological state, as assessed by the BPRS and by the CGI-S, improved significantly (p<0.001) from baseline in both treatment groups. No differences were found between clozapine and quetiapine at each assessment time. The UPDRS score decreased significantly (p<0.05) in the clozapine group, while was almost unchanged in the quetiapine group