Tamiflu (Oseltamivir) Dosing for Influenza
For adults and adolescents ≥13 years, the recommended dose is 75 mg orally twice daily for 5 days for treatment, initiated within 48 hours of symptom onset. 1, 2, 3
Treatment Dosing
Adults and Adolescents (≥13 years)
- 75 mg orally twice daily for 5 days (equivalent to 12.5 mL of oral suspension twice daily if using liquid formulation) 1, 2, 3
- Treatment should be initiated within 48 hours of symptom onset for maximum effectiveness, though should not be withheld in high-risk or hospitalized patients presenting beyond 48 hours 1, 2, 4
Pediatric Patients (≥12 months to 12 years)
Weight-based dosing twice daily for 5 days: 1, 3
- ≤15 kg (≤33 lb): 30 mg twice daily (5 mL twice daily)
- >15-23 kg (>33-51 lb): 45 mg twice daily (7.5 mL twice daily)
- >23-40 kg (>51-88 lb): 60 mg twice daily (10 mL twice daily)
- >40 kg (>88 lb): 75 mg twice daily (12.5 mL twice daily)
Infants (<12 months)
Age-based dosing twice daily for 5 days: 1, 4
- 9-11 months: 3.5 mg/kg per dose twice daily
- Term infants 0-8 months: 3 mg/kg per dose twice daily
- Infants as young as 2 weeks: 3 mg/kg per dose twice daily 1, 3
Preterm Infants
Postmenstrual age-based dosing (gestational age + chronological age) twice daily: 1, 4
- <38 weeks postmenstrual age: 1.0 mg/kg twice daily
- 38-40 weeks postmenstrual age: 1.5 mg/kg twice daily
- >40 weeks postmenstrual age: 3.0 mg/kg twice daily
The lower doses for preterm infants are critical due to immature renal function, and failure to adjust can lead to toxicity. 1
Prophylaxis Dosing
Post-Exposure Prophylaxis
Initiate within 48 hours following close contact with an infected individual: 1, 2
Adults and Adolescents (≥13 years):
Pediatric Patients (1-12 years): Same weight-based doses as treatment, but once daily for 10 days: 1, 3
- ≤15 kg: 30 mg once daily (5 mL once daily)
15-23 kg: 45 mg once daily (7.5 mL once daily)
23-40 kg: 60 mg once daily (10 mL once daily)
40 kg: 75 mg once daily (12.5 mL once daily)
Infants (3-11 months):
- 3 mg/kg once daily for 10 days 1, 3
- Prophylaxis is NOT recommended for infants <3 months unless the situation is judged critical due to limited safety data 1
Seasonal Prophylaxis
- Duration can be extended up to 6 weeks during a community outbreak 2, 3
- In immunocompromised patients, may continue up to 12 weeks 3
Renal Impairment Adjustments
For patients with creatinine clearance 10-30 mL/min: 1, 3
Treatment:
- 75 mg once daily (instead of twice daily) for 5 days 1
Prophylaxis:
Oseltamivir is NOT recommended for end-stage renal disease patients not undergoing dialysis. 1, 3
Administration Considerations
Formulations Available
- Capsules: 30 mg, 45 mg, and 75 mg 1, 4
- Oral suspension: 6 mg/mL concentration when reconstituted 1, 4, 3
Administration Tips
- Can be taken with or without food, though taking with meals significantly improves gastrointestinal tolerability 1, 2, 4
- Capsules can be opened and contents mixed with liquid if patient cannot swallow whole 1, 2
- Nausea and vomiting occur in approximately 5-15% of patients but are typically mild and transient 1
Drug Interaction Warning
- Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir use 1
- Do not use oseltamivir for 14 days after LAIV vaccination unless medically necessary 1, 2
Critical Clinical Pearls
- The 48-hour window for treatment initiation is crucial for maximum benefit, with earlier initiation associated with faster resolution 1, 2, 5
- However, treatment should NOT be withheld in high-risk or hospitalized patients presenting beyond 48 hours 2
- For preterm infants, postmenstrual age-based dosing is essential to avoid toxicity—do not use standard infant dosing 1, 4
- Oseltamivir is safe in pregnancy at standard adult doses throughout all trimesters and is preferred over zanamivir 2