What is the weight-based dose of Oseltamivir (Tamiflu) for influenza treatment?

Oseltamivir Weight-Based Dosing

For children ≥1 year, oseltamivir dosing is weight-based: ≤15 kg receive 30 mg twice daily, >15-23 kg receive 45 mg twice daily, >23-40 kg receive 60 mg twice daily, and >40 kg receive 75 mg twice daily for 5 days of treatment. 1, 2

Adult and Adolescent Dosing (≥13 years)

• The standard dose is 75 mg twice daily for 5 days for treatment of influenza 1, 2
• For prophylaxis, the dose is 75 mg once daily for 10 days after exposure or up to 6 weeks during community outbreaks 1, 2

Pediatric Dosing (Children ≥1 year)

Weight-based dosing is the preferred approach for children 1-12 years of age 1, 2:

• ≤15 kg (≤33 lb): 30 mg twice daily for treatment; 30 mg once daily for prophylaxis 1, 2
• >15-23 kg (33-51 lb): 45 mg twice daily for treatment; 45 mg once daily for prophylaxis 1, 2
• >23-40 kg (51-88 lb): 60 mg twice daily for treatment; 60 mg once daily for prophylaxis 1, 2
• >40 kg (>88 lb): 75 mg twice daily for treatment; 75 mg once daily for prophylaxis 1, 2

Infant Dosing (<1 year)

For term infants, dosing is based on age and weight 1, 2:

• 9-11 months: 3.5 mg/kg per dose twice daily for treatment 1
• 0-8 months (term infants): 3 mg/kg per dose twice daily for treatment 1, 2
• Prophylaxis: 3.5 mg/kg once daily for infants 3-11 months; not recommended for infants <3 months unless situation is critical 1

Important Caveat for Infants

Oseltamivir is FDA-approved for treatment in children as young as 2 weeks of age, but is not FDA-approved for prophylaxis in children <1 year 1, 2

Preterm Infant Dosing

Preterm infants require significantly lower doses due to immature renal function and risk of drug accumulation 1:

Dosing is based on postmenstrual age (PMA) = gestational age + chronological age 1:

• <38 weeks PMA: 1.0 mg/kg per dose twice daily 1
• 38-40 weeks PMA: 1.5 mg/kg per dose twice daily 1
• >40 weeks PMA: 3.0 mg/kg per dose twice daily 1

Critical pitfall: Do not use term infant dosing for preterm infants, as this can lead to dangerously high drug concentrations 1

Renal Impairment Dosing

For patients with creatinine clearance 10-30 mL/min 1, 2:

• Treatment: 30 mg once daily for 5 days 1, 2
• Prophylaxis: 30 mg once daily OR 75 mg every other day for 10 days 1, 2

For patients with creatinine clearance >30-60 mL/min 2:

• Treatment: 30 mg twice daily for 5 days 2
• Prophylaxis: 30 mg once daily 2

Formulation and Administration

• Available as 30 mg, 45 mg, and 75 mg capsules and oral suspension (6 mg/mL when reconstituted) 1, 2
• Administer with food to improve gastrointestinal tolerability, though this is not required 1, 2
• For the 6 mg/mL suspension: 30 mg = 5 mL, 45 mg = 7.5 mL, 60 mg = 10 mL, 75 mg = 12.5 mL 1, 2
• For infants <1 year, use an appropriate measuring device (3-mL or 5-mL oral syringe) instead of the supplied syringe 1, 2

Timing of Therapy

Initiate treatment within 48 hours of symptom onset for maximum benefit 2, 3. Earlier initiation provides greater clinical benefit: treatment within 12 hours reduces illness duration by an additional 74.6 hours compared to treatment at 48 hours 3

Common Adverse Events

• Nausea, vomiting, and diarrhea are the most common adverse events, occurring in approximately 10% of patients 3, 4
• These gastrointestinal symptoms are typically mild, transient (resolving within 1-2 days), and reduced when taken with food 3, 4