Evidence for the use of pimavanserin in the treatment of Parkinson's disease psychosis.

Parkinson's disease (PD) is a progressive neurodegenerative disorder with both motor and nonmotor symptoms (NMS), leading to significant morbidity and caregiver burden. Psychosis is common but is under recognized by physicians. When present, it increases the patient's risk of hospitalization and nursing home placement and caregiver burden. Although the atypical antipsychotic agent, clozapine, has been considered the gold standard treatment, severe agranulocytosis in 0.38% of patients and more commonly milder leukopenia, resulting in frequent blood testing, limit its use. Pimavanserin, a 5HT2A receptor inverse agonist, has been shown to reduce psychosis in PD without worsening motor symptoms. It is therefore a welcome therapeutic option for this devastating NMS.