What is the recommended dose of ondansetron (Zofran) for pediatric patients?

Ondansetron Dosing in Pediatric Patients

The recommended dose of ondansetron for pediatric patients is 0.15 mg/kg per dose (maximum 16 mg per dose) administered intravenously or intramuscularly, with weight-based dosing for oral formulations. 1, 2

Dosing by Route of Administration

Intravenous (IV) Dosing

• Standard dose: 0.15 mg/kg per dose (maximum 16 mg) administered over at least 30 seconds to 15 minutes 2
• For chemotherapy-induced nausea and vomiting: Three doses of 0.15 mg/kg—first dose 30 minutes before chemotherapy, then at 4 and 8 hours after the first dose 2
• For postoperative nausea and vomiting in children >40 kg: 4 mg as a single dose 2
• For postoperative nausea and vomiting in children ≤40 kg: 0.1 mg/kg as a single dose 2

Intramuscular (IM) Dosing

• Same dosing as IV: 0.15 mg/kg per dose (maximum 16 mg) 1
• Particularly useful when IV access is difficult, such as in Food Protein-Induced Enterocolitis Syndrome (FPIES) with moderate symptoms 1

Oral Dosing

• The injectable formulation can be administered orally 3
• Dosing range studied: 0.13-0.26 mg/kg, with no significant difference in efficacy within this range 4

Age-Specific Considerations

Infants and Young Children

• Ondansetron has been studied and used safely in children as young as 6 months of age 5
• A study in 670 pediatric patients aged 1-24 months demonstrated that 0.1 mg/kg IV was effective and well-tolerated 2
• Loading doses of 16 mg/m² (maximum 24 mg) were not associated with increased adverse events in infants under 2 years 6

Children 2-12 Years

• Standard weight-based dosing applies: 0.15 mg/kg (maximum 16 mg) 1, 2
• For a 20 kg child, this equals 3 mg per dose 1

Clinical Context-Specific Dosing

Chemotherapy-Induced Nausea and Vomiting

• High-emetic-risk chemotherapy: 5-HT3 receptor antagonist (ondansetron) combined with dexamethasone and aprepitant 7
• Moderate-emetic-risk chemotherapy: Ondansetron combined with dexamethasone 7
• Low-emetic-risk chemotherapy: Ondansetron or granisetron monotherapy 7
• Dosing: 0.15 mg/kg per dose, three times on day of chemotherapy 2

Gastroenteritis

• The Infectious Diseases Society of America recommends ondansetron for children >4 years with acute gastroenteritis and vomiting 8
• The American Academy of Pediatrics recommends weight-based dosing for persistent vomiting 8
• Typical dose: 0.15 mg/kg, with studies showing efficacy in the range of 0.13-0.26 mg/kg 4

Postoperative Nausea and Vomiting

• Children ≤40 kg: 0.1 mg/kg IV over at least 30 seconds 2
• Children >40 kg: 4 mg IV over at least 30 seconds 2
• Administer immediately before or following anesthesia induction 2

Important Safety Considerations

Cardiac Precautions

• Special caution is warranted in children with heart disease due to potential QT interval prolongation 8, 1
• Rare cases of arrhythmias, bradycardia, and second-degree heart block have been reported 2

Common Adverse Effects

• Most frequently reported: headache, constipation, diarrhea (in chemotherapy patients) 2, 9
• In postoperative setting: wound problems, anxiety, drowsiness, pyrexia 2, 9
• Diarrhea was more common (2%) in the 1-24 month age group compared to placebo (<1%) 2

Dosing Pitfalls to Avoid

• Do not administer a second 4 mg dose postoperatively in adults who fail initial prophylaxis—this does not provide additional benefit 2
• Female patients may experience more frequent moderate adverse events (OR 3.5) 6
• Higher cumulative doses within 24 hours are associated with increased adverse events 6
• Erroneously given second loading doses significantly increase adverse event risk (OR 17.0) 6

Maximum Dosing

• Single dose maximum: 16 mg 1, 2
• Loading doses up to 16 mg/m² (maximum 24 mg) have been studied and found safe in pediatric oncology patients, though this is off-label 6
• No severe life-threatening or lethal adverse events were observed with loading doses in a study of 543 administrations 6

Clinical Pearls

• Ondansetron is generally well-tolerated and rarely necessitates treatment withdrawal 9
• The addition of dexamethasone significantly improves antiemetic efficacy in chemotherapy settings 7, 9
• Within the dose range of 0.13-0.26 mg/kg for gastroenteritis, higher doses were not superior to lower doses 4
• Antiemetic treatment should not replace appropriate fluid and electrolyte therapy in gastroenteritis 8