What is the mechanism of action for 5-HT3 receptor antagonists?

5-HT3 receptor antagonists work by blocking serotonin receptors primarily located in the gastrointestinal tract and the central nervous system. Specifically, they target the 5-HT3 receptor subtype of serotonin, which plays a crucial role in the vomiting reflex. When serotonin binds to these receptors, particularly following chemotherapy or in response to certain gastrointestinal triggers, it can lead to nausea and vomiting. By inhibiting these receptors, 5-HT3 antagonists effectively reduce the sensation of nausea and the subsequent urge to vomit, providing relief in various clinical settings, including postoperative nausea and vomiting or chemotherapy-induced nausea.

The focus on blocking serotonin rather than stimulating its release or interfering with other neurotransmitters like dopamine is key to understanding why this class of medication is particularly effective in managing nausea related to serotonin activation. This action distinguishes 5-HT3 receptor antagonists from other antiemetic agents that may target different pathways in the body.