What is the dose of Fluvir (Oseltamivir) for a 7-month-old weighing 5.890 kg?

Oseltamivir (Fluvir) Dosing for 7-Month-Old Infant Weighing 5.890 kg

For this 7-month-old infant weighing 5.890 kg, the correct dose of oseltamivir syrup is 17.7 mg (approximately 3 mL of the 6 mg/mL suspension) per dose, administered twice daily for treatment or once daily for prophylaxis. 1

Weight-Based Calculation

• The dosing formula for term infants aged 0-8 months is 3 mg/kg per dose. 1
• For this infant: 3 mg/kg × 5.890 kg = 17.67 mg per dose (round to 17.7 mg). 2
• Using the standard 6 mg/mL oral suspension concentration, this equals approximately 3 mL per dose. 1

Treatment vs. Prophylaxis Regimens

• For treatment of influenza: Administer 17.7 mg (3 mL) twice daily for 5 days. 1, 2
• For post-exposure prophylaxis: Administer 17.7 mg (3 mL) once daily for 7 days after last exposure. 1, 2

Administration Instructions

• Oseltamivir can be given without regard to meals, though administration with food may reduce gastrointestinal side effects (nausea, vomiting). 1
• Use a calibrated 3-mL or 5-mL oral syringe for accurate measurement in infants under 1 year—do not use the standard dosing syringe supplied with the medication. 1
• The commercially available suspension has a final concentration of 6 mg/mL after reconstitution. 1

Critical Pitfalls to Avoid

• Do NOT use the fixed-dose categories (≤15 kg = 30 mg) that apply only to children ≥12 months of age—this would result in significant overdosing for this infant. 1, 2
• Do NOT round to convenient volumes—always calculate the precise weight-based dose using 3 mg/kg for infants 0-8 months. 2
• This is NOT preterm infant dosing—preterm infants require lower doses (1.0-1.5 mg/kg depending on postmenstrual age) due to immature renal function. 1 Since this is a 7-month-old, assume term birth unless otherwise specified.

Age-Specific Considerations

• The 3 mg/kg dosing applies specifically to term infants aged 0-8 months. 1
• At 9-11 months, the dose increases to 3.5 mg/kg per dose. 1
• At ≥12 months, weight-based categories shift to fixed doses (30 mg, 45 mg, 60 mg, 75 mg based on weight ranges). 1

Common Adverse Effects in Infants

• Diarrhea is more common in children <1 year of age compared to older children. 1
• Other adverse effects include nausea and vomiting, though these are generally mild and transient. 1, 3