Which of the following antiemetics blocks serotonin receptors both peripherally and centrally?

Ondansetron is a selective serotonin receptor antagonist that primarily targets 5-HT3 receptors. It exerts its antiemetic effects by blocking these receptors in both the central nervous system (CNS) and the gastrointestinal (GI) tract. This dual action is important because it helps in preventing nausea and vomiting caused by various factors, such as chemotherapy, radiotherapy, and postoperative states.

When serotonin is released, particularly in response to chemotherapy or gastrointestinal irritants, it can stimulate these receptors and trigger the vomiting reflex. By blocking the 5-HT3 receptors, ondansetron effectively reduces this reflex both centrally at the level of the brain and peripherally within the GI tract. This makes ondansetron a widely used and effective choice for managing nausea and vomiting in pediatric patients, especially following surgical procedures or during cancer treatments.

The other options mentioned, while having antiemetic properties, do not primarily work through serotonin receptor antagonism. Prochlorperazine and promethazine are typical antipsychotics with antiemetic properties through dopamine receptor antagonism. Metoclopramide, while it has some action on serotonin receptors, primarily functions through dopamine receptor antagonism and also promotes gastric motility. Therefore, ondansetron stands out