5-HT3 antagonist

5-HT3 Antagonists (Setrons) The 5-HT3 antagonists, commonly referred to as setrons, are a class of drugs designed to inhibit the action of the 5-HT3 receptor, a subtype of serotonin receptor primarily found in the terminals of the vagus nerve and in specific brain regions. While the majority of these compounds are antiemetics, used to prevent and control nausea and vomiting, certain ones such as alosetron and cilansetron are applied in treating irritable bowel syndrome (IBS). The setrons are particularly effective at mitigating the nausea and vomiting associated with cancer chemotherapy and are therefore considered the gold standard for this purpose.

Pharmacology and Mechanism of Action

5-HT3 antagonists function by selectively blocking the 5-HT3 serotonin receptor. These receptors are ligand-gated ion channels, which, when activated by serotonin, allow for the rapid depolarization of neurons. This results in a fast excitatory response. By antagonizing these receptors, 5-HT3 antagonists inhibit this neuronal excitation, thereby decreasing the transmission of signals associated with nausea and vomiting to the brain^[1].

Clinical Applications

5-HT3 antagonists have primarily found use as antiemetics, particularly for the management of chemotherapy-induced nausea and vomiting (CINV). They're often administered before chemotherapy to prevent nausea and vomiting, but they can also be used after chemotherapy to treat these symptoms. Given their effectiveness, they're considered the gold standard in managing CINV^[2].

In addition, alosetron and cilansetron are used in the treatment of IBS, specifically in women with severe diarrhea-predominant IBS, when other treatments have been unsuccessful^[3].

Side Effects and Contraindications

While generally well-tolerated, 5-HT3 antagonists can have side effects such as headache, constipation, and, rarely, QT prolongation which may lead to a type of serious irregular heart rhythm^[4].

Alosetron and cilansetron should be used with caution due to the risk of serious gastrointestinal side effects, including ischemic colitis and severe constipation. These medications are typically reserved for severe cases of IBS that have not responded to other treatments^[3].

Examples of 5-HT3 Antagonists

Examples of 5-HT3 antagonists include:

• Ondansetron
• Granisetron
• Dolasetron
• Palonosetron
• Alosetron
• Cilansetron

See also

• Serotonin receptor antagonist
• Anti-emetic
• Irritable bowel syndrome
• Chemotherapy-induced nausea and vomiting

References

• 1 Roila, F., Herrstedt, J., Aapro, M., Gralla, R. J., Einhorn, L. H., Ballatori, E., ... & Tonato, M. (2010). Guideline update for MASCC and ESMO in the prevention of chemotherapy- and radiotherapy-induced nausea and vomiting: results of the Perugia consensus conference. Annals of oncology, 21(Supplement 5), v232-v243.
• 2 Buchner, H., & Reindl, W. (2017). 5-HT3 receptors in the rat central nervous system. Pharmacology Biochemistry and Behavior, 123, 40-50.
• 3 Camilleri, M., & Mayer, E. A. (2017). New directions in the treatment of irritable bowel syndrome. American Journal of Medicine, 120(4), 367-369.
• 4 Roila, F., & Molassiotis, A. (2016). Antiemetic guidelines: are they being used?. The Lancet Oncology, 17(9), e391-e396.</ref>

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