Which antipsychotic is used to treat psychosis or hallucinations in Parkinson's disease?

• A. Risperidone
• B. Clozapine
• C. Olanzapine
• D. Haloperidol

Answer: (A)

In Parkinson’s disease, treating psychosis requires an antipsychotic that won’t worsen motor symptoms. Clozapine fits this need well because it effectively reduces hallucinations and delusions in PD while having a low risk of extrapyramidal symptoms and motor worsening, unlike many other antipsychotics. However, it carries a significant safety requirement: regular blood monitoring for agranulocytosis.

Risperidone and haloperidol can worsen Parkinsonian motor symptoms due to strong dopamine D2 antagonism in the nigrostriatal pathway, making them less suitable. Olanzapine also carries EPS risk and has less robust evidence for PD psychosis. So, among these options, clozapine is the best choice, with the caveat of necessary hematologic monitoring and appropriate clinical use.