What is the recommended dose of Zofran (ondansetron) 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, intramuscularly, or orally, with dosing frequency and route determined by the clinical indication. 1, 2

Standard Weight-Based Dosing

• The fundamental dosing principle is 0.15 mg/kg per dose with an absolute maximum of 16 mg per single dose, regardless of route of administration 1, 2, 3

• For practical application in children aged 2-12 years:

  • 15 kg child: 2.25 mg per dose
  • 20 kg child: 3 mg per dose
  • 25 kg child: 3.75 mg per dose
  • 30 kg child: 4.5 mg per dose
  • 40 kg child: 6 mg per dose
  • >53 kg child: 8 mg per dose (capped at 16 mg maximum) 2

Route-Specific Administration

Intravenous/Intramuscular Dosing

• The same 0.15 mg/kg dose (maximum 16 mg) applies to both IV and IM routes 1, 3
• IV administration should be given over 2-5 minutes to minimize potential QT prolongation 3

Oral Dosing

• Ondansetron oral suspension is available at 6 mg/mL concentration 1
• Can be administered without regard to meals, though food may improve gastrointestinal tolerability 4
• The oral route uses the same weight-based calculation of 0.15 mg/kg per dose 1

Clinical Context-Specific Dosing Algorithms

Chemotherapy-Induced Nausea and Vomiting

High-Emetic-Risk Chemotherapy:

• Administer 0.15 mg/kg IV (maximum 16 mg) 30 minutes before chemotherapy, then repeat at 4 and 8 hours after the first dose 2
• Must be combined with dexamethasone and aprepitant for optimal efficacy 5
• This three-drug combination is strongly recommended by the American Society of Clinical Oncology with intermediate quality evidence 5

Moderate-Emetic-Risk Chemotherapy:

• Ondansetron combined with dexamethasone is the recommended two-drug regimen 5
• If dexamethasone cannot be used, substitute with aprepitant plus ondansetron 5

Low-Emetic-Risk Chemotherapy:

• Ondansetron or granisetron monotherapy is sufficient 5
• Standard dosing of 0.15 mg/kg per dose applies 1

Minimal-Emetic-Risk Chemotherapy:

• No routine antiemetic prophylaxis is recommended 5

Acute Gastroenteritis

For children >4 years with acute gastroenteritis and vomiting:

• Single dose of 0.15 mg/kg orally (maximum 16 mg) is recommended by the Infectious Diseases Society of America 3
• Recent high-quality evidence (2025) demonstrates that providing caregivers with six doses of ondansetron to administer at home in response to ongoing vomiting reduces moderate-to-severe gastroenteritis by 7.4 percentage points compared to placebo 6
• This multidose approach reduced the total number of vomiting episodes within 48 hours (adjusted rate ratio 0.76) without increasing adverse events 6
• Antiemetic treatment should not replace appropriate fluid and electrolyte therapy, which remains the mainstay of treatment 3

Food Protein-Induced Enterocolitis Syndrome (FPIES)

Mild episodes:

• 0.15 mg/kg IM (maximum 16 mg) for children ≥6 months of age 2

Moderate-to-severe episodes:

• 0.15 mg/kg IV or IM (maximum 16 mg) for children ≥6 months of age 2

Radiation-Induced Nausea and Vomiting

• 8 mg oral or 0.15 mg/kg IV once daily before radiation therapy, continued daily on treatment days 1, 2
• For total body irradiation, administer 1.5 hours before each fraction 4

Postoperative Nausea and Vomiting

• 0.1 to 0.15 mg/kg IV (maximum 16 mg) administered before or at the end of anesthesia 7
• Ondansetron combined with dexamethasone is significantly more effective than ondansetron alone 7

Age-Specific Considerations and Safety

Minimum Age Restrictions

• Ondansetron should only be used in children ≥6 months of age for gastroenteritis and FPIES management 2, 3
• For chemotherapy-induced nausea, ondansetron has been studied in children as young as 6 months 5

Cardiac Safety Precautions

• Special caution is warranted in children with underlying heart disease due to ondansetron's potential to prolong the QT interval in a dose-dependent manner 1, 2, 3
• Screen for cardiac history including congenital heart disease or arrhythmias before administration 3
• The pediatric dose of 0.15 mg/kg with a 16 mg maximum provides an appropriate safety margin for QT prolongation risk 2

Common Pitfalls to Avoid

• Never exceed 16 mg as a single dose, even in adolescents or larger children 1, 2
• Do not use ondansetron in infants <6 months of age for gastroenteritis 2, 3
• Avoid using ondansetron as monotherapy for high-emetic-risk chemotherapy when dexamethasone and aprepitant are available 5

Comparative Efficacy Evidence

• Ondansetron demonstrates significantly superior efficacy compared to metoclopramide in pediatric patients, with a better safety profile and lower risk of extrapyramidal reactions 1, 7
• In controlled trials, ondansetron was significantly more effective than metoclopramide or chlorpromazine (both combined with dexamethasone) at reducing acute nausea and vomiting 7
• The addition of dexamethasone significantly improves antiemetic efficacy in chemotherapy settings 1, 7
• Granisetron and palonosetron may be more effective than ondansetron for chemotherapy-induced nausea, though ondansetron remains widely used 5

Adverse Events Profile

• Ondansetron is generally well tolerated in children, rarely necessitating treatment withdrawal 7
• Most frequently reported adverse events include mild-to-moderate headache, constipation, and diarrhea in chemotherapy patients 7
• In postoperative patients, wound problems, anxiety, headache, drowsiness, and pyrexia are most common 7
• In gastroenteritis patients receiving ondansetron, there was a statistically significant increase in diarrhea episodes compared to placebo, though this did not lead to worse clinical outcomes 8