Ondansetron Dosing for a 3-Year-Old Weighing 33 Pounds
For a 3-year-old child weighing 33 pounds (15 kg), the recommended dose of ondansetron is 0.15 mg/kg per dose, which equals approximately 2 mg per dose, with a maximum single dose of 8 mg. 1
Weight-Based Dosing Approach
The most practical approach uses standardized weight-based dosing rather than calculating exact mg/kg doses:
- For children weighing ≤15 kg (≤33 lb): The standard dose is 2-4 mg per dose 1, 2
- This child at exactly 33 pounds falls at the upper end of the ≤15 kg category 1
- The dose can be given orally as a disintegrating tablet, which dissolves on the tongue without water 3
Dosing Frequency and Context
For acute gastroenteritis/vomiting:
- Give a single dose of 2-4 mg orally 1, 4
- May repeat every 8 hours if needed 1
- Maximum daily dose should not exceed 8 mg 1
For chemotherapy-induced nausea:
Important Clinical Considerations
Efficacy within dose range:
- Studies show that doses between 0.13-0.26 mg/kg produce similar efficacy without increased side effects 2
- This means a 2 mg dose (0.13 mg/kg) is as effective as a 4 mg dose (0.27 mg/kg) for this weight 2
- Start with 2 mg to minimize medication exposure while maintaining efficacy 2
Formulation options:
- Oral disintegrating tablets (ODT) are preferred for children who may have difficulty swallowing or ongoing nausea 3
- Standard tablets require swallowing with water 3
Common Pitfalls to Avoid
- Do not exceed 8 mg as a single dose in pediatric patients, even though the calculated 0.15 mg/kg dose might suggest higher amounts 1
- Avoid using adult dosing protocols (8 mg standard dose) in young children 1
- Do not assume higher doses provide better antiemetic control—the dose-response curve plateaus in the 0.13-0.26 mg/kg range 2
Expected Outcomes and Side Effects
Efficacy:
- 58% of children experience complete cessation of vomiting after a single dose 4
- Significantly superior to placebo in preventing emesis 4
Tolerability: