In a patient with Parkinson's disease experiencing nausea, which antiemetic is preferred due to reduced risk of extrapyramidal symptoms?

• A. Metoclopramide
• B. Domperidone
• C. Prochlorperazine
• D. Ondansetron

Answer: (B)

In Parkinson’s disease, it’s crucial to avoid antiemetics that block dopamine receptors in the brain, because that can worsen motor symptoms and provoke extrapyramidal side effects. The best choice is an antiemetic that works mainly outside the brain, so it relieves nausea without interfering with central dopamine pathways.

Domperidone fits this need because it acts peripherally. It blocks dopamine receptors in the gut to improve motility and has only minimal penetration into the central nervous system, so it lowers the risk of extrapyramidal symptoms while still helping with nausea. Its prokinetic effect also helps if nausea is related to delayed gastric emptying, which is common in PD.

In contrast, metoclopramide and prochlorperazine are dopamine D2 antagonists that cross into the central nervous system and can worsen Parkinsonian symptoms or cause new or intensified extrapyramidal effects. Ondansetron targets serotonin receptors and has a very low risk of EPS, but it doesn’t address gastric motility as effectively and may be less beneficial for nausea related to impaired gastric emptying.

So, domperidone is preferred because it provides antiemetic and prokinetic benefits with minimal central dopamine blockade, reducing the likelihood of worsening extrapyramidal symptoms.