Parkinson disease psychosis (PDP) is a common phenomenon in Parkinson disease 
(PD) patients treated with dopaminergic drugs, and is associated with high 
morbidity and mortality. It also correlates with depression and dementia, and 
can contribute to considerable caregiver stress and burnout. While symptoms can 
be relieved by decreasing doses or number of anti-PD medications, this may lead 
to an unacceptable worsening of motor function. When general medical or 
psychiatric conditions have been ruled out, and decreasing dopaminergic agents 
is not effective in treating psychosis, therapies include atypical 
antipsychotics, primarily clozapine and quetiapine. Of these, clozapine is 
effective but is associated with a poor side-effect profile and the necessity 
for frequent blood draws. Clinicians prefer quetiapine for its theoretically 
better safety profile, although there is no evidence for efficacy in treating 
psychosis. All atypical antipsychotics are associated with increased mortality 
in this patient population. Cholinesterase inhibitors can ameliorate psychosis 
symptoms. The serotonin 5-HT2A receptor inverse agonist pimavanserin was 
recently approved by the US FDA for the treatment of PDP and may prove to be a 
more targeted therapy without the downsides of atypical antipsychotics.