Pimavanserin, sold under the brand name Nuplazid, is an atypical antipsychotic which is approved for the treatment of Parkinson's disease psychosis.

[13][14][15] The results of a clinical trial examining the efficacy, tolerability and safety of adjunctive pimavanserin to risperidone and haloperidol were published in November 2012, and the results showed that pimavanserin potentiated the antipsychotic effects of subtherapeutic doses of risperidone and improved the tolerability of haloperidol treatment by reducing the incidence of extrapyramidal symptoms.

[16] The drug met expectations for a Phase III clinical trial for the treatment of Parkinson's disease psychosis,[17] and has completed Phase II trials for adjunctive treatment of schizophrenia alongside an antipsychotic medication.

[19] In April 2016, Nuplazid (pimavanserin) was approved by the FDA for the treatment of hallucinations and delusions associated with Parkinson's disease psychosis.

[22] In June 2018, the FDA approved new dosages of pimavanserin to treat hallucinations and delusions associated with Parkinson's disease psychosis.

[23] In a Phase III, double-blind, randomized, placebo-controlled trial (ClinicalTrials.gov number NTC03325556) pimavanserin was given to people with dementia-related psychosis.

[4] In March 2024, Acadia Pharmaceuticals announced its decision to stop any further clinical trials of pimavanserin after the drug did not improve negative symptoms of schizophrenia better than placebo.

[28] As of November 2024, a phase 2 clinical trial is underway assessing the ability of pimavanserin to block the effects of the serotonergic psychedelic psilocybin.