Rater-blinded, prospective comparison: quetiapine versus clozapine for Parkinson's disease psychosis

Clin Neuropharmacol. 2006 Nov-Dec;29(6):331-7. doi: 10.1097/01.WNF.0000236769.31279.19.


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.

Publication types

  • Comparative Study
  • Evaluation Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Antipsychotic Agents / therapeutic use*
  • Clozapine / therapeutic use*
  • Delusions / drug therapy
  • Delusions / etiology
  • Dibenzothiazepines / therapeutic use*
  • Double-Blind Method
  • Female
  • Hallucinations / drug therapy
  • Hallucinations / etiology
  • Humans
  • Male
  • Neuropsychological Tests
  • Parkinson Disease / complications
  • Parkinson Disease / drug therapy*
  • Prospective Studies
  • Psychotic Disorders / complications
  • Psychotic Disorders / drug therapy*
  • Quetiapine Fumarate
  • Surveys and Questionnaires
  • Treatment Outcome


  • Antipsychotic Agents
  • Dibenzothiazepines
  • Quetiapine Fumarate
  • Clozapine