What are the other 5HT3 (5-hydroxytryptamine 3) antagonists besides ondansetron?

5-HT3 Receptor Antagonists Besides Ondansetron

Besides ondansetron, the other 5-HT3 receptor antagonists include granisetron, dolasetron, palonosetron, ramosetron, and tropisetron. 1

First-Generation 5-HT3 Antagonists

• Granisetron: Available in oral (1-2 mg daily or 1 mg twice daily), intravenous (0.01 mg/kg, maximum 1 mg), and transdermal (3.1 mg/24-hour patch every 7 days) formulations 1
• Dolasetron: Available as oral formulation only (100 mg daily) due to cardiac safety concerns with IV formulation 1
• Tropisetron: Available in oral and intravenous formulations (5 mg) 1, 2
• Ramosetron: Available as intravenous formulation (0.3 mg) 1

Second-Generation 5-HT3 Antagonist

• Palonosetron: Available in oral (0.50 mg) and intravenous (0.25 mg) formulations 1
  • Has approximately 100-fold higher binding affinity for the 5-HT3 receptor compared to first-generation agents 1, 3
  • Has a significantly longer half-life (approximately 40 hours) than other 5-HT3 antagonists 1, 3

Clinical Efficacy Comparisons

• First-generation equivalence: Ondansetron and granisetron show therapeutic equivalence in preventing chemotherapy-induced nausea and vomiting (CINV) 1, 4
• Palonosetron superiority: Multiple studies demonstrate palonosetron's superiority over first-generation 5-HT3 antagonists, particularly for delayed emesis (24-120 hours post-chemotherapy) 1, 5
• Granisetron vs. tropisetron: Evidence suggests granisetron is superior to tropisetron in preventing CINV 1

Dosing Considerations

• Extended-release formulations: Subcutaneous granisetron extended-release injection is available but is NOT interchangeable with intravenous formulations and should not be administered at intervals less than one week 1
• Palonosetron dosing: A single dose may be sufficient prior to a 3-day chemotherapy regimen instead of multiple daily doses of other 5-HT3 antagonists 1

Clinical Applications

• All 5-HT3 antagonists are effective for controlling acute nausea/vomiting associated with cancer chemotherapy 2
• Palonosetron is the only 5-HT3 antagonist specifically indicated for prevention of both acute AND delayed nausea and vomiting associated with moderately emetogenic chemotherapy 3
• For highly emetogenic chemotherapy, palonosetron plus dexamethasone is recommended as first-line therapy 1

Safety Profile

• Common adverse effects across all 5-HT3 antagonists include headache, constipation, dizziness, and fatigue 2
• Safety profiles are generally similar between agents, with no significant differences in frequency or severity of adverse events 3, 5

Clinical Practice Recommendations

• For moderately emetogenic chemotherapy, palonosetron is the preferred 5-HT3 antagonist when available 1
• If palonosetron is not available, granisetron or ondansetron are the preferred first-generation alternatives 1
• For radiation-induced nausea and vomiting, any 5-HT3 antagonist can be used before each fraction 1