Ondansetron Dosing for a 15.8 kg Child
For a child weighing 15.8 kg with normal hepatic and renal function, administer ondansetron 0.15 mg/kg per dose intravenously over 15 minutes, which equals 2.4 mg per dose. 1
Dosing by Clinical Indication
Prevention of Chemotherapy-Induced Nausea and Vomiting
- Administer 0.15 mg/kg per dose (2.4 mg for 15.8 kg child) intravenously over 15 minutes for 3 doses 1
- Give the first dose 30 minutes before starting chemotherapy, then repeat at 4 hours and 8 hours after the first dose 1
- Maximum dose per administration is 16 mg, which does not apply to this weight 1
- Dilution is required: Mix ondansetron in 10-50 mL of 5% Dextrose Injection or 0.9% Sodium Chloride Injection before administration 1
Prevention of Postoperative Nausea and Vomiting
- Administer a single dose of 0.1 mg/kg (1.6 mg for 15.8 kg child) intravenously 1
- Maximum single dose is 4 mg 1
- No dilution required for postoperative nausea and vomiting prophylaxis 1
- Administer immediately before or after induction of anesthesia 1
Evidence Supporting Weight-Based Dosing
The FDA-approved dosing of 0.15 mg/kg per dose for chemotherapy-induced emesis has been validated in multiple pediatric studies showing excellent efficacy and safety 2. In large non-comparative analyses of children receiving this regimen, 70-72% of patients receiving various chemotherapeutic regimens experienced ≤2 emetic episodes 2.
For postoperative nausea and vomiting, the 0.1 mg/kg dose (range 0.075-0.15 mg/kg) demonstrated significantly superior efficacy compared to placebo, droperidol, and metoclopramide in pediatric surgical patients 2.
Administration Considerations
Preparation and Compatibility
- Inspect the solution for particulate matter and discoloration before administration; discard if present 1
- After dilution, do not use beyond 24 hours 1
- Compatible with 0.9% Sodium Chloride, 5% Dextrose, and combinations thereof for 48 hours at room temperature 1
Pharmacokinetic Rationale
- Pediatric patients have increased clearance compared to adults, supporting weight-based rather than fixed dosing 3, 4
- Time to peak concentration is 0.5-2 hours after oral administration, with elimination half-life of approximately 3.5 hours (shorter in children) 5, 4
- Volume of distribution is approximately 160L with 70-76% protein binding 5
Safety Profile
Ondansetron is generally well tolerated in pediatric patients 2. The most common adverse events include:
- Mild to moderate headache 2, 3
- Constipation or diarrhea 2, 4
- Wound problems, anxiety, drowsiness, and pyrexia in postoperative patients 2
Critically, ondansetron does not cause extrapyramidal reactions, unlike metoclopramide, making it particularly advantageous in pediatric populations 4, 6.
Common Pitfalls to Avoid
- Do not skip dilution for chemotherapy-induced nausea and vomiting—this is a mandatory preparation step 1
- Do not mix with alkaline solutions as precipitation may form 1
- Do not exceed 16 mg per dose even in larger children 1
- Do not confuse the chemotherapy dosing regimen (3 doses) with the postoperative regimen (single dose) 1
Enhanced Efficacy Strategies
When ondansetron is combined with dexamethasone, antiemetic efficacy is significantly improved in children receiving chemotherapy 2, 6. This combination should be considered for highly emetogenic chemotherapy regimens 2.