A patient with creatinine clearance of 13 mL/min is nauseous with two episodes of vomiting. Which anti-emetic is most suitable?

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

Answer: (D)

In severe kidney impairment, the safest and most reliable antiemetic is one that won’t accumulate and won’t cause additional central nervous system side effects. Ondansetron works by blocking 5-HT3 receptors both in the gut and the brain, reducing nausea and vomiting. It is mainly processed by the liver, so renal failure is less likely to lead to drug accumulation or unexpected CNS effects compared with other antiemetics that rely on dopamine blockade or antihistamine/anticholinergic actions.

Metoclopramide and prochlorperazine are dopamine antagonists; they can cause extrapyramidal symptoms and other CNS effects, which is less desirable in a patient who is already unwell and possibly dehydrated. Cyclizine is an antihistamine with anticholinergic effects and sedative properties that can worsen confusion or delirium and may contribute to dehydration in someone with vomiting.

Given the need to control vomiting safely in a patient with very reduced renal function, ondansetron is the best choice. Keep in mind it can cause QT prolongation, so monitor electrolytes and avoid in patients with existing significant QT risk.