Psychosis: impact on the patient and family.

Psychosis represents a milestone in the progression of PD, often severely taxing caregivers and frequently warranting nursing-home placement. This step is often necessary because caregivers cannot tolerate, among other stressors, their loved ones' sexual aberrations and irrational accusations (which can be caused by paranoid ideation). Other salient features of parkinsonian psychosis comprise vivid nightmares, which often herald its onset; hallucinations, which are principally visual and stereotypical in content; agitation; aggression; delirium; and confusion that exceeds the typical erosion in mentation. Hallucinosis and paranoid ideation may in turn precipitate weight loss; food may be deemed inedible because of imagined contaminants, for instance, either worm infestations or a delusional fear of poisoning by the caregiver. Parkinsonian psychosis exhibits an age predilection; correlates with the duration of disease and levodopa therapy; and may be associated with increases in the dosage of this agent or other drugs given, either as monotherapy or with levodopa. Levodopa or dopamine agonist toxicity can lead to psychosis because of dopaminergic hypersensitivity. Unfortunately, attempts to diminish this untoward effect (eg, reducing the levodopa dosage, introducing neuroleptics) may curb the psychosis but also erode control of parkinsonian features. To avert this "dopamine dilemma," we have tested a selective serotonin antagonist (ondansetron), which essentially attenuated visual hallucinosis, improved delusional ideation and confusion, and was well tolerated. Other agents that can be tried for parkinsonian psychosis include the atypical neuroleptics olanzapine and clozapine.