Treatment Possibilities for Psychosis in Parkinson's Disease with An Emphasis on the Newly Approved Drug: Pimavanserin

Parkinson's disease (PD) is a progressive neurodegenerative disorder with prominent motor and non-motor symptoms. Psychosis develops in over 40% of PD patients and it is one of the most distressing symptoms for patients and caregivers alike. Until recently, atypical antipsychotics, clozapine and quetiapine were used to treat psychotic symptoms, but treatment was associated with substantial concerns for side-effects of clozapine and unfounded efficacy for quetiapine. Extensive research has shown that the antipsychotic effect of these drugs could be attributed to serotonin 2a receptor (5-HT2A) triggered mechanisms. A selective 5-HT2A inverse agonist, pimavanserin, has been developed, investigated and has gained approval in April 2016 in the US for the treatment of hallucinations and delusions in PD. In this review we primarily focus on psychosis in PD, the current treatment possibilities and the new, emerging therapy, pimavanserin, a selective 5-HT2A inverse agonist. All articles were reviewed in this topic and indexed in PubMed with keywords: Parkinson's disease psychosis, serotonin 2a receptor inverse agonist, clozapine, quetiapine, pimavanserin.