List of products in the National Drug Code with proprietary name . Pimavanserin is used to treat the symptoms of a certain mental/mood disorder (psychosis) that might occur with Parkinson's disease. It helps lessen symptoms such as seeing or hearing things that are not there (hallucinations) and false beliefs (delusions). Pimavanserin belongs to a class of drugs known as atypical antipsychotics, though it works differently from most other drugs in this class.