Ondansetron Dosing for a 20kg Child
For a 20kg child, the recommended dose of ondansetron is 0.15 mg/kg, which equals 3mg per dose, with a maximum single dose of 16mg. 1
Dosing Guidelines by Administration Route
Intravenous (IV) Administration
- For children ≥6 months: 0.15 mg/kg/dose with a maximum of 16 mg per dose 1
- For a 20kg child, this equals 3mg IV
Intramuscular (IM) Administration
- Same dosing as IV: 0.15 mg/kg/dose with a maximum of 16 mg 1
- For a 20kg child, this equals 3mg IM
Oral Administration
- Oral dosing follows similar weight-based guidelines of 0.1-0.15 mg/kg 2
- For a 20kg child, this equals 2-3mg orally
Clinical Applications
Acute Vomiting Episodes
- Ondansetron effectively reduces vomiting episodes in children with acute gastroenteritis 3
- A single oral dose can significantly reduce the risk of recurrent vomiting and need for IV fluids 4
- Number needed to treat is approximately four patients to prevent one child from continued vomiting 3
Food Protein-Induced Enterocolitis Syndrome (FPIES)
- For mild symptoms: Consider ondansetron 0.15 mg/kg IM if child is ≥6 months old 1
- For moderate symptoms: Administer ondansetron 0.15 mg/kg IM if child is ≥6 months old 1
- For severe symptoms: Administer ondansetron 0.15 mg/kg IV if child is ≥6 months old; if IV access is difficult, use IM route 1
Important Considerations
Dose-Response Relationship
- Research shows that within the range of 0.13-0.26 mg/kg, higher doses do not provide superior efficacy compared to lower doses 5
- The standard 0.15 mg/kg dose provides optimal balance of efficacy and safety 5
Safety Concerns
- Cardiac safety concerns exist primarily with high doses (32mg IV) used in cancer chemotherapy, not with the lower doses used for gastroenteritis or postoperative nausea 6
- Monitor for potential side effects including headache, constipation, and diarrhea 2
- Special caution is warranted in children with heart disease due to potential QT interval prolongation 1
Clinical Pearls
- Ondansetron is more effective than metoclopramide or chlorpromazine for controlling nausea and vomiting 2
- Efficacy can be enhanced when combined with dexamethasone in certain clinical scenarios 2
- A single dose is often sufficient to control acute vomiting episodes 3
Conclusion
When administering ondansetron to a 20kg child, the recommended dose is 3mg (calculated at 0.15 mg/kg). This dose provides optimal antiemetic effect while maintaining a favorable safety profile.