What is the recommended dosage frequency of Tamiflu (Oseltamivir) for influenza treatment?

Tamiflu Dosing Frequency

For treatment of influenza, Tamiflu (oseltamivir) should be given twice daily for 5 days in adults and most pediatric patients, while for prophylaxis it is given once daily. 1, 2

Treatment Dosing (Twice Daily for 5 Days)

Adults and Adolescents (≥13 years)

• 75 mg orally twice daily for 5 days 1, 2
• Treatment should be initiated within 48 hours of symptom onset for maximum effectiveness 1, 3
• Earlier initiation provides progressively better outcomes—starting within 12 hours of fever onset can reduce illness duration by an additional 3.1 days compared to starting at 48 hours 3

Pediatric Patients (1-12 years) - Weight-Based Dosing

• ≤15 kg (≤33 lb): 30 mg twice daily 1, 4, 2
• >15-23 kg (>33-51 lb): 45 mg twice daily 1, 4, 2
• >23-40 kg (>51-88 lb): 60 mg twice daily 1, 4, 2
• >40 kg (>88 lb): 75 mg twice daily 1, 4, 2

Infants (<12 months)

• 9-11 months: 3.5 mg/kg per dose twice daily 1
• Term infants 0-8 months: 3 mg/kg per dose twice daily 1, 2
• Preterm infants require postmenstrual age-based dosing:
  • <38 weeks: 1.0 mg/kg twice daily 1
  • 38-40 weeks: 1.5 mg/kg twice daily 1

  • 40 weeks: 3.0 mg/kg twice daily 1

Prophylaxis Dosing (Once Daily)

Adults and Adolescents (≥13 years)

• 75 mg orally once daily 1, 2
• Duration: 10 days for post-exposure prophylaxis 1, 2
• Duration: Up to 6 weeks for seasonal/community outbreak prophylaxis 1, 2
• Duration: Up to 12 weeks in immunocompromised patients 2

Pediatric Patients (1-12 years)

• Use the same weight-based doses as treatment, but once daily instead of twice daily 1, 4
• Duration: 10 days following close contact with infected individual 1, 2

Renal Impairment Adjustments

For patients with creatinine clearance 10-30 mL/min, reduce frequency from twice daily to once daily: 1, 4

• Treatment: 75 mg once daily (instead of twice daily) for 5 days 1
• Prophylaxis: 30 mg once daily OR 75 mg every other day for 10 days 1

Administration Considerations

• Take with food to improve gastrointestinal tolerability—this significantly reduces nausea and vomiting, which occur in approximately 1 in 7 patients 1, 5, 6
• The oral suspension may be used for patients who cannot swallow capsules 1, 2
• Capsules can be opened and mixed with liquid if needed 1

Critical Timing Pitfall

The most common error is delaying treatment initiation. The benefit of oseltamivir decreases progressively with each hour of delay beyond symptom onset. 3 While the 48-hour window is often cited, treatment started within 12-24 hours provides substantially greater benefit—reducing illness duration by up to 40% compared to 25-30% when started at 36-48 hours 3, 7