Treatment of Parkinson's Disease Psychosis

Andrew Schleisman, PharmD Candidate 2017; Mikayla Spangler, PharmD, BCPS; Emily Knezevich, PharmD, BCPS, CDE


US Pharmacist. 2016;41(11):HS-20-HS-26. 

In This Article

Parkinson's Disease Psychosis

The most common symptom of PDP is visual hallucinations, which affect up to 40% of PD patients. Delusions, paranoia, panic attacks, and auditory hallucinations are less common.[6] It is estimated that up to 60% of PD patients experience psychosis, with older patients and those requiring higher doses of dopaminergic drugs at higher risk.[7] Diagnostic criteria for PDP have been established because of the complex differential diagnosis for psychosis. To be diagnosed with PDP, a patient must have all of the following: at least one psychotic symptom; a primary diagnosis of PD; symptoms that are recurrent or continuous for at least 1 month and occur after PD onset; and no other causes of psychosis. Additionally, associated features of PD, such as dementia, and PD drug treatment must be specified.[8] It has been reported that up to 80% of PD patients develop dementia, which confounds the accurate diagnosis of PDP versus the behavioral issues associated with dementia.[7]

The etiology of PDP, which is not clear-cut, involves a potentially complex interaction between internal and external factors.[9] It was previously thought that psychosis in PD patients was primarily iatrogenic—i.e., caused by the medications being used to treat the PD symptoms. On a basic level, psychosis and PD may be considered opposite ends of the dopamine spectrum. Whereas dopamine antagonism is a mechanism employed by medication in the treatment of psychosis, dopaminergic agents are used in the treatment of PD. Of the different subtypes of dopamine receptors, only the D2 receptor is seen in both the mesolimbic/mesocortical pathway, where it is associated with development of psychosis, and the nigrostriatal pathway, where the motor side effects of PD can originate. Therefore, this receptor subtype appears to play a balancing role and has implications for the management of PDP. Other signaling pathways have been linked to the pathophysiology of PDP and point to the disease process of PD as a contributor to the psychosis. These neurotransmitter systems, including serotonin and acetylcholine, are potential targets for drug therapy.[9] A 2016 crosssectional study found that 11% of drug-naïve PD patients had psychosis, supporting the role of the PD process in psychosis development independent of drugtherapy effects.[10]