Tamiflu (Oseltamivir) Dosing for Influenza
Treatment Dosing
For treatment of influenza, initiate oseltamivir within 48 hours of symptom onset at 75 mg orally twice daily for 5 days in adults and adolescents ≥13 years, with weight-based dosing for children. 1, 2
Adults and Adolescents (≥13 years)
- 75 mg orally twice daily for 5 days 1, 3
- Can be taken with or without food, though administration with meals improves gastrointestinal tolerability 1, 2
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
- >15-23 kg (>33-51 lb): 45 mg twice daily
- >23-40 kg (>51-88 lb): 60 mg twice daily
- >40 kg (>88 lb): 75 mg twice daily
Infants (<12 months)
Age-based dosing twice daily for 5 days: 1
- 9-11 months: 3.5 mg/kg per dose
- Term infants 0-8 months: 3 mg/kg per dose
Preterm Infants
Dosing based on postmenstrual age (gestational age + chronological age) twice daily: 1
- <38 weeks postmenstrual age: 1.0 mg/kg per dose
- 38-40 weeks postmenstrual age: 1.5 mg/kg per dose
- >40 weeks postmenstrual age: 3.0 mg/kg per dose
Prophylaxis Dosing
For prophylaxis, administer 75 mg orally once daily in adults for at least 10 days following exposure or up to 6 weeks during community outbreaks. 4, 3
Adults and Adolescents (≥13 years)
- 75 mg orally once daily 1, 4
- Duration: 10 days post-exposure or up to 6 weeks during community outbreak 4, 3
- In immunocompromised patients, may continue up to 12 weeks 3
Pediatric Patients (1-12 years)
Same weight-based doses as treatment, but once daily instead of twice daily for 10 days post-exposure or up to 6 weeks during outbreak: 1, 3
- ≤15 kg: 30 mg once daily
- >15-23 kg: 45 mg once daily
- >23-40 kg: 60 mg once daily
- >40 kg: 75 mg once daily
Infants (3-11 months)
- 3 mg/kg once daily for 10 days 1
- Prophylaxis not recommended for infants <3 months unless situation is critical due to limited safety data 1
Renal Impairment Adjustments
Patients with creatinine clearance 10-30 mL/min require dose reduction to prevent toxicity. 1, 2
Treatment Dosing
Prophylaxis Dosing
- 30 mg once daily for 10 days OR 75 mg every other day for 10 days (5 total doses) 1
Oseltamivir is not recommended for end-stage renal disease patients not undergoing dialysis. 3
Formulations and Administration
Available Forms
Suspension Dosing Volumes
Administration Tips
- Capsules can be opened and mixed with liquid if patient cannot swallow whole 1
- Taking with food significantly reduces nausea and vomiting, which occur in 5-15% of patients 1, 2
- If commercial suspension unavailable, pharmacies can compound using capsule contents mixed with simple syrup or Ora-Sweet SF to achieve 6 mg/mL concentration 1
Critical Timing and Considerations
Treatment must be initiated within 48 hours of symptom onset for maximum effectiveness. 1, 2 Evidence suggests that starting beyond 48 hours provides minimal benefit in most populations, though critically ill ICU patients with H1N1 may benefit from treatment initiated up to 5 days after symptom onset. 5
Do not withhold treatment while awaiting laboratory confirmation in high-risk patients with suspected influenza. 1 Empiric treatment should be started promptly based on clinical suspicion during influenza season.
Vaccine Interaction
Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir use, and do not use oseltamivir for 14 days after LAIV vaccination, as the antiviral may interfere with vaccine effectiveness. 1, 4
Common Pitfalls
- Do not use double-dose oseltamivir (150 mg twice daily) as studies show no survival benefit and similar tolerability concerns 5, 6
- Standard 5-day treatment duration is sufficient for most patients; extended therapy beyond 5 days lacks supporting evidence except possibly in critically ill H1N1 ICU patients 5
- Oseltamivir is not a substitute for annual influenza vaccination and should not replace vaccination strategies 3