Which antipsychotic is less likely to precipitate worsening of Parkinson disease symptoms, and is often considered safer in this context?

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

Answer: (B)

When treating someone with Parkinson disease, you want an antipsychotic that minimizes blocking dopamine in the nigrostriatal pathway, because strong D2 blockade there worsens motor symptoms like tremor, rigidity, and bradykinesia. Haloperidol does this very strongly and is most likely to worsen PD symptoms. Among the options, clozapine has the least impact on motor function because its D2 antagonism is relatively weak at therapeutic doses and it has notable 5-HT2A antagonism, which together reduce the risk of extrapyramidal symptoms. This makes it the safer choice for PD patients who need an antipsychotic. Keep in mind clozapine requires regular monitoring for agranulocytosis. Risperidone and olanzapine can still cause EPS at certain doses, and haloperidol is more likely to worsen motor symptoms, so clozapine stands out as safer in this context.