What is the dosage of oseltamivir (antiviral medication) in capsule form for an infant?

Oseltamivir Dosage for Infants in Capsule Form

For infants, oseltamivir capsules should be opened and the contents mixed with a sweetened liquid to mask the bitter taste, with dosing based on age and weight: 3 mg/kg twice daily for term infants 0-8 months and 3.5 mg/kg twice daily for infants 9-11 months, for 5 days. 1

Weight-Based Dosing for Infants

The appropriate dosing of oseltamivir for infants is weight-based and age-dependent:

• For term infants 0-8 months: 3 mg/kg per dose twice daily for 5 days 1
• For infants 9-11 months: 3.5 mg/kg per dose twice daily for 5 days 1, 2
• For preterm infants (based on postmenstrual age):
  • <38 weeks postmenstrual age: 1 mg/kg per dose twice daily 1, 3
  • 38-40 weeks postmenstrual age: 1.5 mg/kg per dose twice daily 1, 3

  • 40 weeks postmenstrual age: 3 mg/kg per dose twice daily 1, 3

Administration of Capsule Form for Infants

Since infants cannot swallow capsules, the medication must be properly prepared:

• Oseltamivir is available in 30 mg, 45 mg, and 75 mg capsules 1
• For administration to infants, the capsules should be opened and the contents mixed with a sweetened liquid to mask the bitter taste 1, 4
• An appropriate measuring device such as a 3-mL or 5-mL oral syringe should be used to measure the dose instead of the syringe supplied with commercial suspension 1
• Administration with food may improve gastrointestinal tolerability 1, 3, 4

Safety and Efficacy Considerations

• Oseltamivir is FDA-approved for treatment of children as young as 2 weeks of age 1, 4
• Clinical studies have shown that the recommended weight-based dosing achieves therapeutic drug exposures in infants 2, 5
• Common adverse events include gastrointestinal effects such as vomiting and diarrhea 4, 5
• Treatment should be initiated within 48 hours of symptom onset for maximum effectiveness 3, 6

Special Considerations

• For infants with renal insufficiency, dose adjustment is necessary based on creatinine clearance 1, 4
• Consultation with a pediatric infectious disease specialist is recommended for extremely preterm infants (<28 weeks) 3
• The American Academy of Pediatrics recommends against using oseltamivir for chemoprophylaxis in infants <3 months due to limited safety and efficacy data in this age group 1

Calculating the Correct Dose

To calculate the correct dose from capsules:

1. Determine the infant's weight in kilograms
2. Multiply the weight by the appropriate dose (3 mg/kg or 3.5 mg/kg depending on age)
3. Open the capsule that is closest to the calculated dose
4. Mix the contents with an appropriate amount of sweetened liquid
5. Administer the correct proportion of the mixture to achieve the calculated dose 1

Research has confirmed that these dosing recommendations produce adequate systemic exposure to oseltamivir carboxylate (the active metabolite) in infants, with an acceptable safety margin 2, 5, 7.