OBJECTIVE: To summarize and evaluate the existing literature regarding 
medications to treat Parkinson's disease (PD) psychosis.
DATA SOURCES: MEDLINE (1946 to March 2017), EMBASE (1980 to March 2017), CINAHL 
(1982 to March 2017), and PsychInfo (1887 to March 2017) were searched using the 
following terms: Parkinson disease, Parkinson's disease, psychotic disorders, 
psychosis, delusions, and hallucinations.
STUDY SELECTION AND DATA EXTRACTION: The search was limited to randomized 
controlled trials (RCTs) reporting human outcomes. Data extracted included the 
following: study design, population, setting, intervention, control, outcomes 
related to psychosis and safety, and potential biases assessed using Cochrane 
Collaboration's Risk of Bias Assessment Tool.
DATA SYNTHESIS: After assessment, 16 of 235 studies were included; 11 articles 
reported comparisons between active drug and placebo, whereas 5 compared 
clozapine and an active comparator. Placebo-controlled trials demonstrated 
benefit for clozapine (n = 2) and pimavanserin (n = 2), with no firm benefits 
observed for quetiapine (n = 4) or olanzapine (n = 3). Comparative studies 
demonstrated improved efficacy in symptom scores when clozapine or comparator 
agent (n = 2, quetiapine; n = 1, olanzapine; n = 1, risperidone; and n = 1, 
ziprasidone) was assessed alone. However, no comparator data suggest that one 
agent is better than another, and none are yet available for pimavanserin. 
Overall risk of bias across all studies was moderate to high.
CONCLUSIONS: Despite lack of rigor in study designs, published data to date 
suggest that clozapine and pimavanserin should be considered drugs of choice to 
treat PD psychosis.