What is the recommended dose and administration of Zofran (ondansetron) via intramuscular (IM) injection for an 11-month-old patient?

Ondansetron IM Injection for 11-Month-Old Infant

For an 11-month-old infant, ondansetron IM injection should be dosed at 0.15 mg/kg per dose (maximum 16 mg), and is only recommended for patients 6 months of age and older in specific clinical contexts such as food protein-induced enterocolitis syndrome (FPIES) or chemotherapy-induced nausea and vomiting.

Age-Specific Dosing Guidelines

The standard IM dose for infants 6 months and older is 0.15 mg/kg per dose, with a maximum of 16 mg per dose. 1

• This dosing applies specifically to moderate-to-severe presentations requiring antiemetic intervention 1
• The FDA-approved dosing for chemotherapy-induced nausea is 0.15 mg/kg per dose for 3 doses in patients 6 months and older, though this refers to IV administration 2
• For FPIES management, the American Academy of Allergy, Asthma & Immunology recommends IM ondansetron 0.15 mg/kg/dose (maximum 16 mg) for patients 6 months and older 1

Clinical Context and Indications

Ondansetron IM is primarily indicated for specific conditions in this age group, not routine gastroenteritis:

• FPIES (Food Protein-Induced Enterocolitis Syndrome): IM ondansetron is recommended for moderate presentations with >3 episodes of emesis and mild lethargy 1
• Chemotherapy-induced nausea/vomiting: Ondansetron has demonstrated efficacy in pediatric oncology patients, though IV route is typically preferred 3, 4
• NOT recommended for routine viral gastroenteritis: Recent evidence suggests limited clinical benefit and potential for increased diarrhea as a side effect 5

Route-Specific Considerations

IM administration is specifically useful when IV access is delayed or difficult to obtain:

• In severe FPIES presentations, if IV line placement is delayed due to difficult access, IM ondansetron 0.15 mg/kg should be administered while attempting IV access 1
• IM administration has an onset of action within approximately 5 minutes in pediatric patients 1
• The IM route provides an alternative when oral administration is not feasible due to persistent vomiting 3

Important Safety Considerations and Caveats

Special caution is warranted in infants with cardiac conditions:

• Ondansetron can prolong the QT interval, requiring caution in children with heart disease 1
• Monitor for potential cardiac effects, particularly with repeated dosing 1

Age-specific limitations:

• Ondansetron should only be used in patients 6 months of age and older 1
• At 11 months, this patient meets the minimum age requirement
• Efficacy and safety data are more robust for older children 3, 4

Dose-response considerations:

• Within the dose range of 0.13-0.26 mg/kg, higher doses do not provide superior efficacy or increased side effects 6
• The standard 0.15 mg/kg dose represents an evidence-based middle ground 1

Administration Technique

For IM injection in an 11-month-old infant:

• Administer in the anterolateral thigh (preferred site for infants) 1
• Use appropriate needle length for IM injection in infants 1
• Monitor the patient for 4-6 hours from onset of symptoms for resolution 1

When NOT to Use Ondansetron IM

Avoid routine use in simple viral gastroenteritis:

• Recent evidence shows ondansetron provides limited clinical benefit in routine gastroenteritis 5
• Diarrhea occurs 2-3 times more frequently with ondansetron compared to placebo 5
• Standard oral rehydration solution remains first-line for uncomplicated gastroenteritis 5

Reserve IM ondansetron for:

• Confirmed or suspected FPIES with moderate-to-severe symptoms 1
• Chemotherapy-induced nausea when IV access is problematic 2, 3
• Situations where persistent vomiting prevents oral rehydration and IV access is difficult 1