What is the recommended dose of ondansetron (Zofran) for a 1-year-old child weighing 24 pounds?

Ondansetron Dosing for a 1-Year-Old Weighing 24 Pounds

Yes, ondansetron can be given to a 1-year-old child weighing 24 pounds (approximately 11 kg), at a dose of 0.15 mg/kg, which equals approximately 1.65 mg per dose. 1

Weight-Based Calculation

• For this specific child (24 lbs = 10.9 kg): The standard pediatric dose of 0.15 mg/kg translates to approximately 1.6-1.7 mg per dose 1
• The American Academy of Pediatrics recommends the standard pediatric dosing of 0.15 mg/kg per dose (maximum 16 mg) for children, with route and frequency depending on clinical indication 1

Practical Dosing Considerations

• For children ≤15 kg (which includes this 11 kg child): Some guidelines reference a fixed dose of 30 mg twice daily for treatment, though this appears to be for oseltamivir (influenza medication) rather than ondansetron based on the evidence context 2
• The weight-based calculation of 0.15 mg/kg is the most appropriate approach for ondansetron in this age group 1, 3

Route of Administration

• Oral route: 0.15 mg/kg (approximately 1.6-1.7 mg for this child) 1, 3
• Intravenous route: 0.15 mg/kg if oral administration is not feasible 3, 4
• Onset of action: Oral ondansetron peaks at approximately 1 hour, with a half-life of 3.5 hours 4

Clinical Context and Frequency

For Acute Gastroenteritis with Vomiting

• Single oral dose has been shown to reduce recurrent vomiting, need for IV fluids, and hospital admissions 5, 6
• During the observation period in the emergency department, ondansetron significantly reduced vomiting episodes compared to placebo 6
• Additional doses can be given every 8 hours if needed, though a single dose is often sufficient for gastroenteritis 6

For Chemotherapy-Induced Nausea/Vomiting

• Dosing schedule: 0.15 mg/kg given 30 minutes before chemotherapy, then repeated at 4 and 8 hours after the first dose 1
• Multiple studies using 5 mg/m² or 0.15 mg/kg doses showed effective control of chemotherapy-induced emesis 3, 7

Critical Safety Considerations

• Age restriction for FPIES: The American Academy of Pediatrics advises against using ondansetron in infants under 6 months of age, but this 1-year-old child is well above that threshold 1
• QT interval prolongation: Ondansetron can prolong the QT interval in a dose-dependent manner, though the pediatric dose of 0.15 mg/kg with a 16 mg maximum provides an appropriate safety margin 1
• Tolerability: Ondansetron is generally well tolerated in children, with the most common adverse events being mild headache, constipation, and diarrhea 3
• Diarrhea consideration: In gastroenteritis patients, ondansetron may be associated with slightly increased diarrhea episodes during the 48-hour follow-up period 6

Common Pitfalls to Avoid

• Do not exceed the maximum single dose of 16 mg, even though this is not relevant for this small child 1
• Avoid combining with other medications that prolong QT interval without appropriate monitoring 1
• Ensure adequate hydration is maintained, as ondansetron controls vomiting but does not address the underlying fluid deficit 5, 6
• Monitor for excessive sedation if combined with other CNS depressants, though ondansetron alone rarely causes significant sedation 3, 4

Efficacy Data

• In children receiving ondansetron for chemotherapy, complete control of nausea and vomiting was achieved in a substantial proportion of patients 3, 7
• For acute gastroenteritis, ondansetron significantly reduced IV fluid requirements (P=0.015) and hospital admission rates (P=0.007) compared to placebo 6
• The median number of vomiting episodes in the ED was 0 in both ondansetron and placebo groups, but the rank sum was significantly lower with ondansetron (P=0.001) 6