In this episode, we review the pharmacology, indications, adverse effects, and unique drug characteristics of 5-HT3 receptor antagonists such as ondansetron (Zofran) and palonosetron (Aloxi).

Key Concepts

1. There are four 5-HT3 (serotonin subtype 3) receptor antagonists on the market: ondansetron, granisetron, dolasetron, and palonosetron. These have primarily been studied for acute chemotherapy-induced nausea and vomiting (within 24 hours of chemotherapy administration) and for post-operative nausea and vomiting.
2. When used for chemotherapy-induced nausea/vomiting, 5-HT3 receptor antagonists are given prior to chemotherapy (usually 30-60 minutes before) on day #1. They are not given on subsequent days because they are not as effective for delayed nausea and vomiting.
3. Palonosetron has the longest half-life, longer binding affinity to the 5-HT3 receptor, and trends towards having the best efficacy among the 5-HT3 receptor antagonists.
4. 5-HT3 receptor antagonists are associated with QTc prolongation and may cause headache, dizziness, constipation, or diarrhea. Their association with an increased risk of serotonin syndrome is controversial and not supported from a mechanistic perspective.

References

• Simino GP, Marra LP, Andrade EI, et al. Efficacy, safety and effectiveness of ondansetron compared to other serotonin-3 receptor antagonists (5-HT3RAs) used to control chemotherapy-induced nausea and vomiting: systematic review and meta-analysis. Expert Rev Clin Pharmacol. 2016;9(9):1183-1194. doi:10.1080/17512433.2016.1190271
• Tricco AC, Soobiah C, Blondal E, et al. Comparative efficacy of serotonin (5-HT3) receptor antagonists in patients undergoing surgery: a systematic review and network meta-analysis. BMC Med. 2015;13:136. Published 2015 Jun 18. doi:10.1186/s12916-015-0371-y
• Hesketh PJ, Kris MG, Basch E, et al. Antiemetics: ASCO Guideline Update. J Clin Oncol. 2020;38(24):2782-2797. doi:10.1200/JCO.20.01296
• Herrstedt J, Clark-Snow R, Ruhlmann CH, et al. 2023 MASCC and ESMO guideline update for the prevention of chemotherapy- and radiotherapy-induced nausea and vomiting. ESMO Open. 2024;9(2):102195. doi:10.1016/j.esmoop.2023.102195
• Rojas-Fernandez CH. Can 5-HT3 Antagonists Really Contribute to Serotonin Toxicity? A Call for Clarity and Pharmacological Law and Order. Drugs Real World Outcomes. 2014;1(1):3-5. doi:10.1007/s40801-014-0004-3
• Li WS, van der Velden JM, Ganesh V, et al. Prophylaxis of radiation-induced nausea and vomiting: a systematic review and meta-analysis of randomized controlled trials. Ann Palliat Med. 2017;6(2):104-117. doi:10.21037/apm.2016.12.01