What is the appropriate ondansetron (Zofran) dose for a child weighing 27 lb (approximately 12.2 kg)?

Ondansetron Dosing for a 27-Pound Child

For a child weighing 27 pounds (12.2 kg), the appropriate ondansetron dose is 0.15 mg/kg, which equals approximately 1.8 mg per dose. 1

Weight-Based Dosing Calculation

• A 27-pound child weighs approximately 12.2 kg 1
• Using the standard pediatric dosing of 0.15 mg/kg: 12.2 kg × 0.15 mg/kg = 1.83 mg per dose 1, 2
• The maximum single dose should not exceed 16 mg 1

Age Considerations

• This dosing is appropriate for children ≥6 months of age 1
• For infants <6 months, ondansetron should only be used if the situation is judged critical due to extremely limited safety and efficacy data 1

Practical Administration

Oral formulation (if available):

• Ondansetron oral solution is typically available as 4 mg/5 mL concentration 2
• For a 1.8 mg dose, administer approximately 2.25 mL of the 4 mg/5 mL solution 2
• Oral disintegrating tablets dissolve on the tongue without water, which may be preferred for young children 3

Intravenous/Intramuscular route:

• The same 0.15 mg/kg dose (1.8 mg) can be given IV or IM 1, 4
• IM route is preferred when IV access is difficult or delayed 1
• IV route is recommended when IV access is already established 1

Dosing Frequency and Timing

• For chemotherapy-induced nausea: Give the first dose 30 minutes before chemotherapy, then repeat every 8 hours as needed 5, 4
• For postoperative nausea: Single dose given perioperatively 2
• For acute gastroenteritis/vomiting: Single dose, with monitoring over 4-6 hours 1

Important Clinical Caveats

• Do not use in infants <6 months unless the clinical situation is critical, as safety data is extremely limited in this age group 1
• No dosage adjustment is needed for renal impairment 5
• Ondansetron reaches peak concentration 0.5-2 hours after oral administration, so timing before anticipated nausea is important 6
• The elimination half-life is approximately 3.5-3.8 hours in children 6, 7

Common Pitfalls to Avoid

• Avoid underdosing: Some providers mistakenly use fixed doses (like 2 mg or 4 mg) for all children, but weight-based dosing of 0.15 mg/kg is more appropriate and effective 1, 2
• Don't delay administration: For chemotherapy-induced nausea, ondansetron should be given at least 30 minutes before the emetogenic stimulus 6, 4
• Consider combination therapy: For highly emetogenic situations, adding dexamethasone significantly improves antiemetic efficacy 2, 8