Impact of pimavanserin on prescribing practices in parkinson disease

Parkinson disease psychosis (PDP) is a common complication of PD. Until 2016, the only drugs available to treat PDP in the U.S. were antipsychotics with variable degrees of dopamine-receptor antagonism (DRA) that may worsen PD motor symptoms. We evaluated the impact that pimavanserin, a selective serotonin receptor inverse agonist/antagonist atypical antipsychotic (AAP) with no known DRA, had on PDP treatment practices in a commercially insured population.

We included adults diagnosed with PD who filled at least one AAP prescription from 2016 to 2022. AAP dispensings were categorized into (1) pimavanserin, (2) clozapine and quetiapine (i.e., PDP-"preferred" mixed receptor antagonist AAPs), and (3) the remaining AAPs (i.e., PDP-"nonpreferred" mixed receptor antagonist AAPs). Trends in quarterly dispensing rates per 1000 persons treated were compared across categories. Secondary analyses focused on the 65+ subpopulations insured by Medicare Advantage programs.

Dispensing rates varied between 4 and 697/1000 persons treated for pimavanserin, 1434-1821 for preferred, and 394-746 for nonpreferred AAPs. Pimavanserin dispensings surpassed the nonpreferred category after quarter 3 of 2018. However, preferred AAPs, particularly quetiapine, remained the most dispensed category in the sixth year after pimavanserin's approval. We observed similar trends among Medicare Advantage enrollees.

The availability of pimavanserin was followed by a decline in the use of the most harmful AAPs in persons living with PD. Quetiapine remained the most prescribed AAP. Comparative safety and effectiveness studies are needed to define the relative risks and benefits of treatment options in PDP.