What is the mechanism of action of ondansetron?

• A. Dopamine receptor antagonist
• B. 5-HT3 receptor antagonist
• C. Muscarinic receptor agonist
• D. Neurokinin-1 receptor antagonist

Answer: (B)

Ondansetron functions as a 5-HT3 receptor antagonist, which is pivotal in its mechanism of action. It primarily targets serotonin receptors located in the gastrointestinal tract and the central nervous system. By blocking these 5-HT3 receptors, ondansetron effectively prevents the action of serotonin, which plays a significant role in triggering nausea and vomiting. Serotonin is released when the gastrointestinal tract is stimulated, particularly during chemotherapy, radiation, or after surgery, leading to the activation of these receptors and the subsequent development of nausea.

When ondansetron inhibits the stimulation of these receptors, it significantly reduces the incidence of nausea and vomiting, making it an essential medication for managing these symptoms in various clinical settings. Its efficacy in protecting patients from chemotherapy-induced nausea and postoperative nausea demonstrates its critical role in supportive care for patients undergoing cancer treatment or surgical procedures.