5-HT3 receptor antagonists (also called serotonin receptor antagonists or serotonin blockers) are a class of medicines that are used for the prevention and treatment of nausea and vomiting, particularly that caused by chemotherapy, radiation therapy, or postoperatively. 5-HT3 is an abbreviation for serotonin that may also be written as 5-hydroxytryptamine.
Cells lining the gastrointestinal tract release serotonin when damaged by chemotherapy and radiation therapy. This serotonin binds to serotonin receptors on nerves that transmit impulses to the vomiting center within the brain, which in turn stimulates other nerves involved in the vomit reflex. 5-HT3 receptor antagonists prevent serotonin from binding to 5-HT3 receptors in the small intestine thereby reducing the likelihood of nausea and vomiting. The way 5-HT3 receptor antagonists work to prevent postoperative nausea and vomiting is less well understood.
The first generation 5-HT3 receptor antagonists include dolasetron, granisetron, and ondansetron. Despite variations in their chemical structures and absorption rates, they all work in the same way and are well tolerated. The oral formulations are just as effective at preventing nausea and vomiting as the intravenous forms.
Palonosetron is a second-generation serotonin blocker. It has a greater affinity for serotonin receptors than first generation agents, which increases its duration of effect. Palonosetron is also thought to have an effect on 5-HT3 receptors in the vomiting center and chemoreceptor trigger zone as well, not just the small intestine. It is approved for both acute and delayed chemotherapy-induced nausea and vomiting.
