- Adult
- CINV (highly emetogenic): 24 mg oral once, 30 min before chemotherapy; OR 0.15 mg/kg IV (max 16 mg) over 15 min, 30 min before chemo, repeated at 4 and 8 hours. CINV (moderately emetogenic): 8 mg oral 30 min before chemo, then 8 mg every 8 hours for 1-2 days; OR 8 mg IV as a single dose. RINV: 8 mg oral 1-2 hours before radiotherapy, then 8 mg every 8 hours. PONV: 16 mg oral 1 hour before anesthesia; OR 4 mg IV over 2-5 min at induction or post-op.
- Pediatric
- CINV (6 months to 18 years): 0.15 mg/kg IV (max 16 mg) over 15 min, starting 30 min before chemo, repeated at 4 and 8 hours. PONV (1 month to 12 years, weight ≤40 kg): 0.1 mg/kg IV (max 4 mg) at induction or post-op. PONV (>12 years or >40 kg): 4 mg IV at induction or post-op.
- Renal adjustment
- No dosage adjustment is required for patients with renal impairment. Ondansetron is metabolized hepatically; renal excretion of unchanged drug is minimal (~5%).
- Hepatic adjustment
- In patients with severe hepatic impairment (Child-Pugh score ≥10), do not exceed a total daily dose of 8 mg (oral or IV). Monitor for increased adverse effects (headache, constipation, QT prolongation).
- Geriatric
- No specific dosage adjustment required based on age alone. However, use with caution in elderly patients with cardiac conditions due to increased risk of QT prolongation and electrolyte abnormalities. Monitor ECG if on other QT-prolonging medications.
- Max dose
- 24 mg single oral dose (CINV highly emetogenic); 16 mg single IV dose; 8 mg/day maximum for severe hepatic impairment
