Objective: To compare the safety and efficacy of quetiapine versus clozapine for the treatment of psychosis in patients with Parkinson's disease (PD).
Methods: Twenty-seven patients with PD and recent-onset psychosis were randomly allocated to 2 arms of 22 weeks' treatment with quetiapine or clozapine after 2 weeks of adjustment of antiparkinsonian medications. Assessment was done by a blinded neuropsychologist using the Clinical Global Impression of Change (CGIC) questionnaire and the Neuropsychiatric Inventory (NPI). Mixed-effect models were used to compare CGIC and Neuropsychological Inventory scores over time between the 2 groups.
Results: Both drugs were equally effective based on the CGIC. Clozapine had a trend over quetiapine in controlling the frequency of hallucinations (P = 0.097) and a significant advantage in reducing delusions (P = 0.011). However, one patient in the clozapine arm developed leukopenia. None of the drugs worsened parkinsonism.
Conclusions: Clozapine and quetiapine are effective atypical neuroleptics for the treatment of psychotic symptoms in PD. Clozapine had greater efficacy in reducing hallucinations and delusions frequency, but its use is associated with an increased risk of leukopenia.