Serotonin (5-HT3) antagonists are used to treat nausea and vomiting caused by chemotherapy, radiation therapy, or surgery. They also have other uses, such as managing irritable bowel syndrome. These medications work by blocking serotonin receptors in the brain and gut. Serotonin antagonists come in different forms, including oral tablets, orally disintegrating tablets, injections, and patches. Examples include ondansetron, alosetron (Lotronex), and granisetron (Sancuso).