Which antiemetic works by blocking serotonin 5-HT receptors?

• A. Block lymphocyte proliferation.
• B. Direct effect on smooth muscle.
• C. Monoclonal antibody that binds to tumor necrosis factor.
• D. Block serotonin 5-HT receptors.

Answer: (D)

Blocking serotonin 5-HT receptors interrupts a key vomiting signal. Serotonin released in the gut activates 5-HT3 receptors on vagal afferent nerves, which send signals to the brain’s vomiting center. An antiemetic that blocks these receptors prevents this pathway from triggering nausea and vomiting. Drugs that do this include ondansetron, granisetron, dolasetron, and palonosetron, making them especially useful for chemotherapy- and post-surgical nausea and vomiting.

Other options describe actions that don’t target this serotonin-mediated route: reducing lymphocyte proliferation (immunomodulation), a general direct effect on smooth muscle (not specifically the emetic pathway), or a monoclonal antibody against TNF (an anti-inflammatory mechanism). None of these block serotonin receptors to prevent vomiting.