Tamiflu (Oseltamivir) Dosage Recommendations
Treatment Dosing
For adults and adolescents ≥13 years, the recommended dose is 75 mg orally twice daily for 5 days, initiated within 48 hours of symptom onset. 1, 2
Adults and Adolescents (≥13 years)
- 75 mg twice daily for 5 days (equivalent to 12.5 mL of oral suspension twice daily) 1, 2
- Treatment must be started within 48 hours of symptom onset for maximum effectiveness 1, 3
- Can be taken with or without food, though administration with meals significantly improves gastrointestinal tolerability 1, 3
Pediatric Patients (≥12 months to 12 years) - Weight-Based Dosing
The American Academy of Pediatrics recommends the following weight-based dosing for 5 days, twice daily: 1, 2
- ≤15 kg (≤33 lb): 30 mg twice daily (5 mL of oral suspension)
- >15-23 kg (>33-51 lb): 45 mg twice daily (7.5 mL of oral suspension)
- >23-40 kg (>51-88 lb): 60 mg twice daily (10 mL of oral suspension)
- >40 kg (>88 lb): 75 mg twice daily (12.5 mL of oral suspension)
Infants (<12 months)
Age-based dosing is recommended for infants: 1, 3
- 9-11 months: 3.5 mg/kg per dose twice daily for 5 days
- Term infants 0-8 months: 3.0 mg/kg per dose twice daily for 5 days
Preterm Infants
Dosing is based on postmenstrual age (gestational age + chronological age) due to immature renal function: 1, 3
- <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
Prophylaxis Dosing
For post-exposure prophylaxis in adults, the dose is 75 mg once daily for 10 days, initiated within 48 hours of close contact with an infected individual. 1, 2
Adults and Adolescents (≥13 years)
- 75 mg once daily (12.5 mL of oral suspension once daily) 1, 2
- Post-exposure prophylaxis: 10 days following close contact with infected individual 1, 2
- Seasonal/community outbreak prophylaxis: Up to 6 weeks during community outbreak 4, 2
- Immunocompromised patients: May continue up to 12 weeks 2
Pediatric Patients (1-12 years) - Weight-Based Dosing
Same weight-based doses as treatment, but once daily instead of twice daily for 10 days: 1, 2
- ≤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)
- 3.0 mg/kg once daily for 10 days 1
- Prophylaxis is not recommended for infants <3 months unless the situation is judged critical due to limited safety data 1
Renal Impairment Adjustments
For patients with creatinine clearance 10-30 mL/min, reduce the treatment dose to 75 mg once daily (instead of twice daily) for 5 days. 1, 2
Treatment Dosing
Prophylaxis Dosing
- CrCl 10-30 mL/min: Either 30 mg once daily for 10 days OR 75 mg every other day for 10 days (5 total doses) 1, 3
Important Caveat
- Oseltamivir is not recommended for patients with end-stage renal disease not undergoing dialysis 2
Formulations and Administration
Available Formulations
- Capsules: 30 mg, 45 mg, and 75 mg strengths 1, 2
- Oral suspension: 6 mg/mL concentration when reconstituted 1, 2
- Capsules can be opened and contents mixed with liquid if patient cannot swallow whole 1
Administration Pearls
- Taking with food significantly reduces nausea and vomiting, which occur in approximately 5-15% of patients 1, 3
- Use an appropriate oral dosing device that accurately measures volume in mL 2
- For infants requiring small volumes, ensure dosing device can measure accurately 2
Critical Timing Considerations
The 48-hour window from symptom onset is crucial for treatment efficacy - earlier initiation is associated with faster resolution of illness. 1, 3, 5 Studies show that treatment initiated within 24 hours of symptom onset reduces illness duration by 37-40% compared to placebo, versus 25-30% when started within 36 hours. 5
For prophylaxis, initiation within 48 hours of close contact with an infected individual is recommended for post-exposure prophylaxis. 1
Drug Interactions
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 efficacy. 1, 4