Pharmacological interventions for psychosis in Parkinson's disease patients

Psychosis is a common problem for people treated for Parkinson's disease. The syndrome is quite stereotypic, with hallucinations being the most common, followed by delusions. While the hallucinations are usually not very bothersome, the delusions are typically paranoid in nature. Treatment is often, but not always, required.

This article reviews the therapeutic approaches of this syndrome focusing on drug treatments used once contributory factors have been removed. This includes a review of the evidence supporting the use of clozapine and, most recently, pimavanserin, the first drug with antipsychotic efficacy that has no effect on dopamine. Treatment with second generation antipsychotic drugs and cholinesterase inhibitors are also reviewed.

Clozapine and pimavanserin have proven efficacy for Parkinson's disease psychosis (PDP), without impairing motor function. In clozapine's favor are its antipsychotic benefits seen within 1 week and its effectiveness in improving tremor in PD. However, this is counterbalanced by the need for blood monitoring, despite the extremely low doses used, and sedation. Pimanvanserin is well tolerated, without sedation or other significant side effects. Its onset of benefit, however takes 4-6 weeks. While quetiapine is also frequently used, its efficacy is not supported by double blinded, randomized trials.