Ondansetron Pediatric Dose Calculator
Weight-based ondansetron dosing for children, with maximum doses, age limits and sources. Enter age and weight for the dose in mg and syrup mL, tablets or injection volume.
Pediatric dosing
Vomiting in acute gastroenteritis (oral)
Nausea and vomiting — IV/IM (hospital) Hospital
Ondansetron dose chart by age and weight
Vomiting in acute gastroenteritis (oral). Weights are WHO/IAP reference medians for age — always dose on the measured weight.
| Age | Weight | Dose (mg) | Oral solution 4 mg/5 mL | Syrup 2 mg/5 mL | Frequency |
|---|---|---|---|---|---|
| 1 month | 4.3 kg | Below minimum age | |||
| 3 months | 6.1 kg | Below minimum age | |||
| 6 months | 7.6 kg | Below minimum weight | |||
| 9 months | 8.6 kg | 1.29 mg | 1.6 mL | 3.2 mL | Single dose; may repeat after ≥8 hours (max 3 doses in 24 h) |
| 1 year | 9.3 kg | 1.4 mg | 1.7 mL | 3.5 mL | Single dose; may repeat after ≥8 hours (max 3 doses in 24 h) |
| 18 months | 10.6 kg | 1.59 mg | 2 mL | 4 mL | Single dose; may repeat after ≥8 hours (max 3 doses in 24 h) |
| 2 years | 11.8 kg | 1.77 mg | 2.2 mL | 4.4 mL | Single dose; may repeat after ≥8 hours (max 3 doses in 24 h) |
| 3 years | 14.1 kg | 2.11 mg | 2.6 mL | 5.3 mL | Single dose; may repeat after ≥8 hours (max 3 doses in 24 h) |
| 4 years | 16.2 kg | 4 mg | 5 mL | 10 mL | Single dose; may repeat after ≥8 hours (max 3 doses in 24 h) |
| 5 years | 17.5 kg | 4 mg | 5 mL | 10 mL | Single dose; may repeat after ≥8 hours (max 3 doses in 24 h) |
| 6 years | 19 kg | 4 mg | 5 mL | 10 mL | Single dose; may repeat after ≥8 hours (max 3 doses in 24 h) |
| 8 years | 24.4 kg | 4 mg | 5 mL | 10 mL | Single dose; may repeat after ≥8 hours (max 3 doses in 24 h) |
| 10 years | 31.1 kg | 8 mg | 10 mL | — | Single dose; may repeat after ≥8 hours (max 3 doses in 24 h) |
| 12 years | 39.4 kg | 8 mg | 10 mL | — | Single dose; may repeat after ≥8 hours (max 3 doses in 24 h) |
Strengths in the calculator
- Syrup 2 mg/5 mL (Oral)
- Oral solution 4 mg/5 mL (Oral)
- Orally disintegrating tablet 2 mg (Oral — do not split)
- Orally disintegrating tablet 4 mg (Oral — do not split)
- Orally disintegrating tablet 8 mg (Oral — do not split)
- Injection 2 mg/mL (Intravenous / Intramuscular)
Different strength on your bottle? Use “Different strength on the bottle?” under the result.
Safety
Contraindications and cautions
- Congenital long-QT syndrome; uncorrected hypokalaemia or hypomagnesaemia; concurrent QT-prolonging drugs.
Pregnancy and breastfeeding
Legacy FDA category B. Possible small increase in oral clefts with first-trimester use; reserve for vomiting not controlled by other measures.
Probably compatible; limited data.
Clinical notes
Helps the child tolerate ORS — it does not replace rehydration. ODTs should not be split. Rule out surgical causes (bilious vomiting, abdominal distension) before treating.
Adult and adolescent (≥40 kg) dose
4–8 mg — Every 8 hours if needed (max 8 mg per dose, 24 mg per day).
Other names and brands
- India: Emeset, Ondem, Vomikind
- USA: Zofran
- UK: Zofran
Brand examples only — products and strengths vary by country. Always check the label.
Frequently asked questions
What is the ondansetron dose for children?
Vomiting in acute gastroenteritis (oral): <15 kg: 0.15 mg/kg/dose · single dose; may repeat after ≥8 hours (max 3 doses in 24 h) · max 4 mg/dose; 15 to 30 kg: 4 mg per dose · single dose; may repeat after ≥8 hours (max 3 doses in 24 h); >30 kg: 8 mg per dose · single dose; may repeat after ≥8 hours (max 3 doses in 24 h). Usual duration: Usually a single dose. Always use the child's measured weight and check the strength on the bottle.
How many mL of syrup 2 mg/5 mL for an 11.8 kg child?
For vomiting in acute gastroenteritis (oral), an 11.8 kg child (about 2 years) needs 1.77 mg per dose — 4.4 mL of Syrup 2 mg/5 mL, single dose; may repeat after ≥8 hours (max 3 doses in 24 h). Recalculate with the child's actual weight.
From what age can ondansetron be given?
Age range in PediaRx: Gastroenteritis: ≥6 months (≥8 kg) · IV: ≥1 month. The calculator does not calculate a dose below 1 month. Each indication can have its own age and weight limits, shown with its regimen.
Is ondansetron safe in pregnancy?
Legacy FDA category B. Possible small increase in oral clefts with first-trimester use; reserve for vomiting not controlled by other measures.
Sources and editorial process
- Oral ondansetron for gastroenteritis in a pediatric emergency department (Freedman et al., N Engl J Med 2006) — New England Journal of Medicine
- BNF for Children — Ondansetron — NICE / BMJ Group / Royal Pharmaceutical Society
- Ondansetron — US prescribing information — DailyMed (U.S. National Library of Medicine)
Dosing data last updated 2026-09-27. PediaRx is built and maintained by Dr. Shounak Pal, MBBS (Medical Officer, Government of West Bengal, India — founder and developer of PediaRx). Every regimen is encoded with explicit units, maximum doses and age/weight limits and is checked by automated tests before publication. Report an error: hello@pediarx.com.
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Clinical disclaimer: reference tool for qualified health professionals. Verify every dose against current guidance and the product label before prescribing.
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