Management of Parkinson's disease psychosis—a European perspective

Hallucinations and delusions are among the most disabling long-term complications of Parkinson's disease (PD). Their pathogenesis is based on a complex interaction of neurodegeneration in critical areas for visual and cognitive processing and PD medication effects. Management rests on the identification and treatment of acute triggers, simplification of PD medication and treatment with antipsychotics. Despite the high prevalence of psychosis in advanced PD there is still a lack of familiarity with its manifestations and therapeutic approaches. This gap is further enhanced by recent developments in drug availability and therapeutic monitoring. Pimavanserin is the only approved drug for the treatment of PD psychosis in the U.S., but currently not marketed elsewhere. The aim of this review is to provide an update on the management options for PD psychosis in other regions of the world with a focus on clinical practice in Europe. Quetiapine and clozapine remain cornerstones of treatment of PD psychosis in Europe. Despite limited evidence for efficacy, quetiapine is often used as first-line therapy, whereas severe PD psychosis usually requires treatment with clozapine, with clozapine demonstrating efficacy without worsening of motor symptoms in randomised, controlled trials. Other antipsychotics should be avoided in PD psychosis due to their ineffectiveness or high potential for worsening parkinsonian motor symptoms. Novel drugs with a better risk-benefit ratio in the treatment of PD psychosis are needed. Non-pharmacological treatments should be explored in relation to their potential to prevent or mitigate psychotic reactions in prospective studies.