Ondansetron
Ondansetron is a serotonin 5-HT3 receptor antagonist used mainly as an antiemetic (to treat nausea and vomiting), often following chemotherapy. It affects both peripheral and central nerves[1]. Ondansetron reduces the activity of the vagus nerve, which deactivates the vomiting center in the medulla oblongata, and also blocks serotonin receptors in the chemoreceptor trigger zone. It has little effect on vomiting caused by motion sickness, and does not have any effect on dopamine receptors or muscarinic receptors.