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

Ondansetron (Zofran) Dosing for Pediatric Patients

Standard Weight-Based Dosing

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 this same weight-based approach applied across most clinical contexts. 1, 2

Practical Weight-Based Calculations

For typical pediatric weights, the 0.15 mg/kg dosing translates to: 1

• 25 kg child: 3.75 mg per dose
• 30 kg child: 4.5 mg per dose
• 35 kg child: 5.25 mg per dose
• 40 kg child: 6 mg per dose

Route-Specific Considerations

• IV/IM administration: 0.15 mg/kg (maximum 16 mg) 1, 2
• Oral administration: 0.1 mg/kg or 5 mg/m² body surface area 3
• Oral suspension: Available at 6 mg/mL concentration; can be given without regard to meals, though food may improve GI tolerability 2

Context-Specific Dosing Algorithms

Chemotherapy-Induced Nausea and Vomiting

High-emetic-risk chemotherapy (e.g., cisplatin): 1, 2

• Administer 0.15 mg/kg IV or IM (maximum 16 mg) 30 minutes before chemotherapy
• Repeat at 4 hours and 8 hours after the first dose
• Combine with dexamethasone and aprepitant for optimal control 2, 3

Moderate-emetic-risk chemotherapy: 2, 3

• Same ondansetron dosing as above
• Combine with dexamethasone (significantly more efficacious than ondansetron alone) 2

Low-emetic-risk chemotherapy: 2, 3

• Ondansetron monotherapy at 0.15 mg/kg is appropriate

Acute Gastroenteritis with Vomiting

For children >4 years with acute gastroenteritis: 2, 3

• Ondansetron facilitates oral rehydration
• Use weight-based dosing: 0.15 mg/kg (maximum 16 mg)
• Critical caveat: Antiemetic treatment does not replace appropriate fluid and electrolyte therapy, which remains the cornerstone of management 2, 3
• Ensure adequate hydration before or during ondansetron administration 3

Food Protein-Induced Enterocolitis Syndrome (FPIES)

Only use in children ≥6 months of age: 1, 3

Mild episodes (1-2 emetic episodes, no lethargy): 3

• Consider ondansetron 0.15 mg/kg IM (maximum 16 mg)
• Attempt oral rehydration

Moderate episodes (>3 emetic episodes with mild lethargy): 3

• Ondansetron 0.15 mg/kg IM or IV (maximum 16 mg)
• Consider IV line with normal saline bolus 20 mL/kg

Severe episodes (>3 episodes with severe lethargy, hypotonia, ashen or cyanotic appearance): 3

• Requires aggressive fluid resuscitation with isotonic fluids
• Ondansetron as adjunct

Radiation-Induced Nausea and Vomiting

Single high-dose or daily fractionated radiotherapy: 1, 2

• 8 mg oral or 0.15 mg/kg IV once daily
• Administer 1-2 hours before radiation therapy
• Continue daily on treatment days

Postoperative Nausea and Vomiting

For surgical procedures with high PONV risk (e.g., tonsillectomy, strabismus repair): 4

• 0.075-0.15 mg/kg IV or 0.1 mg/kg oral
• Administer before or during anesthesia induction
• Combining with dexamethasone or propofol-based anesthesia significantly improves efficacy 4

Pediatric Head Trauma

For children with traumatic brain injury presenting with nausea/vomiting: 3

• Ondansetron is the first-line antiemetic due to superior safety profile
• Avoids extrapyramidal effects that could interfere with neurological monitoring
• Do not use dopaminergic antagonists like metoclopramide for multiple consecutive days due to high incidence of dystonic reactions 3

Age-Specific Considerations

• Infants ≥6 months: Standard weight-based dosing applies; safe and studied 2, 3
• Infants <6 months: Avoid for FPIES management per American Academy of Pediatrics 1, 3
• Children 2-12 years: 0.15 mg/kg (maximum 16 mg) 2
• Adolescents 12-18 years: Same weight-based dosing; may use adult dose of 8 mg three times daily if weight appropriate 5
• Pediatric patients have increased clearance compared to adults, with half-life approximately 3.5 hours 6, 7

Critical Safety Considerations

QT Interval Prolongation

Exercise special caution in children with pre-existing heart disease: 2, 3

• Ondansetron can prolong QT interval in a dose-dependent manner 1
• The 0.15 mg/kg dose with 16 mg maximum provides appropriate safety margin 1
• Monitor electrolytes (particularly potassium and magnesium) as abnormalities increase QT prolongation risk 3
• Obtain baseline ECG if known cardiac disease 3

Maximum Dosing Limits

• Single dose maximum: 16 mg per dose 1, 2, 3
• Loading doses: 16 mg/m² (maximum 24 mg) IV have been studied and appear safe, though severe adverse events occurred in 0.9% (95% CI 0.4-2.1%) 8
• Female patients and higher cumulative doses associated with more frequent adverse events 8

Common Pitfalls to Avoid

Do not use ondansetron as a substitute for proper hydration: 2, 3

• In gastroenteritis, fluid and electrolyte therapy remains the primary treatment
• Ondansetron facilitates rehydration but does not replace it

Avoid dopaminergic antagonists in pediatrics when ondansetron is available: 3

• Metoclopramide carries significant risk of extrapyramidal reactions
• Ondansetron demonstrates superior efficacy and safety profile 4

Do not exceed maximum single dose of 16 mg: 1, 2, 3

• Even in larger adolescents, cap individual doses at 16 mg

Ensure adequate hydration before administration: 3

• Particularly important in gastroenteritis and FPIES settings

Alternative Agents When Ondansetron Contraindicated

If ondansetron cannot be used due to QT concerns or allergy: 3

• Granisetron: Another 5-HT3 antagonist with similar favorable neurological safety profile
• Dexamethasone: Highly effective for nausea, particularly when combined with other antiemetics; serves dual purpose in head trauma (reduces cerebral edema while providing antiemetic effects)