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ALIMENTARY TRACT AND METABOLISM › ANTIEMETICS AND ANTINAUSEANTS › ANTIEMETICS AND ANTINAUSEANTS › Serotonin (5HT3) antagonists
ondansetron
A04AA01
Forms & Strengths
- Oral tablet: 4 mg, 8 mg, 24 mg
- Orally disintegrating tablet (ODT): 4 mg, 8 mg
- Oral solution: 4 mg/5 mL
- Solution for injection: 2 mg/mL, 4 mg/mL
Adult Dosing
- Chemotherapy-induced nausea and vomiting (CINV): 8 mg orally 30 min before emetogenic chemo, then 8 mg 8 hours later
- Highly emetogenic chemo: 24 mg orally once with dexamethasone 30 min before chemo
- Radiotherapy-induced nausea and vomiting: 8 mg orally 1 to 2 hours before radiation
- Postoperative nausea and vomiting (PONV): 16 mg orally 1 hour before anesthesia, or 4 mg IV/IM at induction or post-op
Pediatric Dosing
- CINV (Children 6-11 years): 4 mg orally 30 min before chemo, then 4 mg 4 and 8 hours after first dose
- CINV (Children >=12 years): 8 mg orally 30 min before chemo, then 8 mg 8 hours later, then 8 mg every 12 hours for 1-2 days
- PONV (Children 1 month to 12 years, >40 kg): 4 mg IV single dose
- PONV (Children 1 month to 12 years, <=40 kg): 0.1 mg/kg IV single dose
Indications
- Prevention of nausea and vomiting associated with highly and moderately emetogenic cancer chemotherapy
- Prevention of nausea and vomiting associated with radiotherapy
- Prevention of postoperative nausea and vomiting
Mechanism of Action
- Selective 5-HT3 receptor antagonist
- Blocks serotonin receptors centrally in the chemoreceptor trigger zone and peripherally on vagal nerve terminals in the intestine
Contraindications
- Hypersensitivity to ondansetron or other 5-HT3 receptor antagonists
- Concomitant use of apomorphine due to risk of profound hypotension and loss of consciousness
- Congenital long QT syndrome
Adverse Reactions
- Headache
- Fatigue and malaise
- Constipation
- Diarrhea
- QT prolongation and Torsades de Pointes
- Serotonin syndrome when combined with other serotonergic agents
- Elevated liver transaminases
Drug Interactions
- Apomorphine (contraindicated)
- QT-prolonging agents (e.g., antipsychotics, antiarrhythmics, macrolides) increase risk of ventricular arrhythmias
- Serotonergic drugs (e.g., SSRIs, SNRIs, MAOIs, tramadol) increase risk of serotonin syndrome
- CYP3A4 inducers (e.g., phenytoin, carbamazepine, rifampin) may decrease ondansetron plasma concentrations
Curated Content: Needs Vetting Before Put to Clinical Use