Ondansetron Dosing for a 6-Month-Old, 8.647 kg Infant
Direct Answer
For this 6-month-old infant weighing 8.647 kg, administer 1.3 mg of ondansetron (approximately one-third of a 4 mg ODT), based on the standard pediatric dose of 0.15 mg/kg. 1, 2
Dose Calculation
- Weight-based calculation: 8.647 kg × 0.15 mg/kg = 1.3 mg per dose 1, 2
- Maximum single dose: 16 mg (not applicable for this patient) 1, 2
- Practical administration: Cut or dissolve one 4 mg ODT and administer approximately one-third of the tablet 1
Age Appropriateness
- Ondansetron is safe for infants ≥6 months of age, making this patient eligible for treatment 1, 2
- The American Academy of Allergy, Asthma, and Immunology specifically recommends 0.15 mg/kg/dose for children ≥6 months 2
Administration Considerations for ODT Formulation
- ODT tablets can be dissolved in a small amount of water to facilitate accurate partial dosing when only 4 mg tablets are available 1
- Alternatively, the tablet can be carefully divided, though this is less precise than liquid formulation
- Administration can occur without regard to meals, though food may improve GI tolerability 1
Alternative Routes if ODT Not Feasible
- Intramuscular (IM) route: Same dose of 1.3 mg (0.15 mg/kg) if oral route is not tolerated 2
- Intravenous (IV) route: Same dose of 1.3 mg (0.15 mg/kg) if IV access is available 2
- All three routes (oral, IM, IV) use identical weight-based dosing in pediatrics 1, 2
Critical Safety Considerations
- QT prolongation risk: Exercise special caution if this infant has any underlying heart disease 1, 2
- Baseline ECG should be considered if cardiac history is present or if repeated dosing is anticipated 1
- Monitor for adverse effects including headache (though less common in infants), constipation, and diarrhea 3
Common Pitfalls to Avoid
- Do not round up to 2 mg or use half a tablet (2 mg) as this would exceed the recommended dose by 50% and increase risk of adverse effects
- Avoid concurrent use with other QT-prolonging medications (e.g., certain antibiotics, antiarrhythmics) 4
- This medication should not replace appropriate fluid and electrolyte therapy if the infant has gastroenteritis-related vomiting 1
Dosing Frequency
- Standard interval: Can be repeated every 8 hours if needed, though single-dose therapy is often sufficient for acute vomiting 3
- Maximum daily doses: Typically limited to 2-3 doses in 24 hours for this age group 3