What is the recommended dose of Zofran (ondansetron) for a 9-month-old child?

Ondansetron (Zofran) Dosing for a 9-Month-Old Child

For a 9-month-old infant, ondansetron is not FDA-approved, but when clinically indicated, the recommended dose is 0.15 mg/kg per dose given every 8 hours as needed.

Dosing Considerations for Infants

Ondansetron (Zofran) dosing in infants requires careful consideration as there are limited FDA-approved indications for this age group. The available evidence suggests the following approach:

Weight-Based Dosing

• For infants 0-8 months: 3 mg/kg per dose, twice daily for treatment 1
• For infants 9-11 months: 3.5 mg/kg per dose, twice daily for treatment 1

Important Clinical Considerations

1. FDA Approval Status:

   • Ondansetron is not officially FDA-approved for infants under 1 year
   • Clinical use in this age group is based on extrapolation from older children and limited pediatric studies

2. Route of Administration:

   • Oral disintegrating tablets or oral solution are preferred in the outpatient setting
   • Intravenous administration may be considered in hospital settings when oral intake is not possible

3. Duration of Treatment:

   • For acute vomiting: Use for shortest duration necessary, typically 24-48 hours
   • Prolonged use should be avoided due to limited safety data in this age group

Efficacy and Safety Considerations

Research studies have demonstrated that ondansetron is effective for controlling vomiting in pediatric populations, though specific data for infants under 1 year is limited:

• Ondansetron has shown good efficacy in preventing acute nausea and vomiting in children receiving chemotherapy and in post-operative settings 2
• In dose-response studies, doses between 0.13-0.26 mg/kg showed similar efficacy with no additional benefit at higher doses within this range 3

Potential Side Effects

When administering ondansetron to infants, monitor for:

• Diarrhea (most common side effect in young children)
• Headache (difficult to assess in infants)
• QT interval prolongation (rare but serious)
• Constipation

Clinical Decision Algorithm

1. Assess need for antiemetic therapy:

   • Consider if vomiting is severe and causing dehydration
   • Rule out surgical causes of vomiting
   • Determine if oral rehydration is failing due to persistent emesis

2. Calculate appropriate dose:

   • Weigh the infant to determine accurate dosing
   • Calculate at 0.15 mg/kg per dose

3. Monitor response:

   • Assess for reduction in vomiting episodes within 30-60 minutes
   • Evaluate ability to tolerate oral fluids
   • Monitor for diarrhea, which may worsen with ondansetron

Cautions and Contraindications

• Use with caution in infants with congenital heart disease or family history of long QT syndrome
• Avoid in infants with known hypersensitivity to ondansetron
• Consider potential drug interactions, particularly with medications that prolong QT interval

While ondansetron can be effective for controlling vomiting in infants, its use should be reserved for situations where the benefit clearly outweighs potential risks, particularly when dehydration is a concern and other supportive measures have failed.