Certified Specialist In Oncology Nutrition (CSO) Practice Exam

Which drug is a selective 5-HT3 receptor antagonist commonly used to prevent chemotherapy-induced nausea and vomiting?

Dexamethasone Ondansetron Lorazepam Megestrol acetate

Correct Answer:

Ondansetron

Explanation:

The main idea is that blocking serotonin signaling at the 5-HT3 receptor prevents the vomiting reflex triggered by chemotherapy. Ondansetron is a selective antagonist of the 5-HT3 receptor, meaning it specifically blocks serotonin’s action at those receptors located in the gut and in the brain’s chemoreceptor trigger zone. By inhibiting this pathway, it effectively reduces nausea and vomiting associated with chemotherapy, especially in the acute phase right after treatment. This makes it a go-to antiemetic for CINV. Other options listed have different roles: a corticosteroid with antiemetic effects but not a 5-HT3 blocker, a benzodiazepine mainly for anxiety and anticipatory nausea, and a progestin used to stimulate appetite rather than prevent nausea.

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