Clozapine is an effective drug for treating psychosis in Parkinson's disease 
(PDP) and is registered as such in the Netherlands. However, clozapine can have 
adverse effects, including agranulocytosis. The new drug pimavanserin was 
recently registered in the United States for the treatment of PDP.<br/> AIM: To 
review the literature on pimavanserin and discuss the position it currently 
occupies in the Netherlands as a potential treatment for PDP.<br/> METHOD: 
Systematic search of the literature.<br/> RESULTS: We found reports on four 
randomised controlled trials (RCTs), one review and six articles about the 
pharmacokinetics and pharmacodynamics of pimavanserin. Pimavanserin is an 
effective treatment for PDP, and, like clozapine, it has very few negative 
effects on motor skills. However, all of the RCTs were funded by the 
manufacturer of pimavanserin and the trials were conducted in a very selective 
patient population. This means that results cannot be generalised. Long-term 
results are not yet available. In earlier trials clozapine was shown to have a 
greater and faster antipsychotic effect. Many clinicians and psychiatrists have 
a great deal of experience with this drug. Another important point is that 
no-one has yet conducted a trial comparing clozapine and pimavanserin.<br/> 
CONCLUSION: Given that the current second drug of choice, namely quetiapine, has 
not been found to be effective for PDP, we are of the opinion that - if 
pimavanserin is registered in the Netherlands - pimavanserin could be used when 
the current drug of choice, clozapine, is not completely effective or is poorly 
tolerated. For patients who have cognitive impairments in addition to psychosis, 
we advise testing the patient's reaction to a cholinesterase inhibitor before 
starting the patient on a course of antipsychotics.