5HT, antagonist is:

(D) Ondansetron # 5-HT3 antagonists are a class of medications which act as receptor antagonists at the 5-hydroxytryptamine-3 receptor (5-HT3 receptor), a subtype of serotonin receptor found in terminals of the vagus nerve and in certain areas of the brain. With the notable exception of alosetron and cilansetron, which are used in the treatment of irritable bowel syndrome, all 5-HT3 antagonists are antiemetics, used in the prevention and treatment of nausea and vomiting. They are particularly effective in controlling the nausea and vomiting produced by cancer chemotherapy, and are considered the gold standard for this purpose.> Therapeutic uses:1. In the prevention and treatment of chemotherapy-induced nausea and vomiting (CINV), especially that caused by highly emetogenic drugs such as cisplatin2. In the prevention and treatment of radiation-induced nausea and vomiting (RINV), when needed, and postoperative nausea and vomiting (PONV).3. 5-HT3 antagonists are ineffective in controlling motion sickness.4. Investigational useful in treating antipsychotic-induced tardive dyskinesia in people with schizophrenia.> Available agents:1. Ondansetron2. Tropisetron3. Granisetron4. Dolasetron5. Palonosetron6. Ramosetron7. Alosetron and8. cilansetron> Certain medications such as cisapride, renzapride and metoclopramide, although not 5-HT3 antagonists proper, possess some weak antagonist effect at the 5-HT3 receptor. Galanolactone, a diterpenoid found in ginger, is a 5-HT3 antagonist and is believed to at least partially mediate the anti-emetic activity of this plant.