INTRODUCTION: Parkinson´s disease (PD) is a synucleinopathy that affects 
millions of people worldwide and leads to progressive disability. Psychosis is 
highly prevalent in PD patients and is associated with poor prognosis. Until 
April 2016, there were no licensed drugs available in the United States of 
America (USA) for the treatment of PD psychosis (PDP). Pimavanserin is the first 
Food and Drug Administration approved medicine for the treatment of 
hallucinations and delusions associated with PDP.
AREAS COVERED: A MEDLINE literature search, publicly available information 
provided by ACADIA Pharmaceuticals, and expert opinion were used for this 
review. A review of PDP, its current treatment and limitations is followed by 
the rationale for development of pimavanserin. The mechanism of action, 
preclinical data, pharmacokinetics, pharmacodynamics, and clinical data 
supporting the efficacy and safety of pimavanserin in PDP are reviewed. We also 
describe the potential benefits of pimavanserin in other contexts such as 
schizophrenia and sleep disorders.
EXPERT OPINION: Pimavanserin is an antipsychotic with a unique mechanism of 
action (5-HT2A receptor inverse agonist) and no measurable dopaminergic 
activity; it has been demonstrated to be efficacious, well tolerated and safe 
for the treatment of PDP. The development of pimavanserin as an antipsychotic 
represents a major breakthrough in the pharmacotherapy of psychotic symptoms 
associated with PD.