Tamiflu (Oseltamivir) Dosing Recommendations
For adults and adolescents ≥13 years, the standard treatment dose is 75 mg orally twice daily for 5 days, and the prophylaxis dose is 75 mg once daily for 10 days. 1, 2
Treatment Dosing
Adults and Adolescents (≥13 years)
- 75 mg orally twice daily for 5 days 3, 1, 2
- Treatment should be initiated within 48 hours of symptom onset for maximum benefit, though should not be withheld in high-risk or hospitalized patients presenting beyond this window 1, 4
- Taking with food may improve gastrointestinal tolerability 3, 5, 2
Pediatric Patients (≥12 months to 12 years)
Weight-based dosing twice daily for 5 days: 3, 1, 2
- ≤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)
- 9-11 months: 3.5 mg/kg per dose twice daily for 5 days 1, 5
- Term infants 0-8 months: 3 mg/kg per dose twice daily for 5 days 3, 1
Preterm Infants
Dosing based on postmenstrual age (gestational age + chronological age): 3, 1, 5
- <38 weeks: 1.0 mg/kg twice daily
- 38-40 weeks: 1.5 mg/kg twice daily
- >40 weeks: 3.0 mg/kg twice daily
The lower doses for preterm infants are critical due to immature renal function, which can lead to drug accumulation at standard term infant doses. 3, 5
Prophylaxis Dosing
Adults and Adolescents (≥13 years)
- 75 mg orally once daily for 10 days (post-exposure prophylaxis) 1, 4, 2
- May be extended up to 6 weeks for seasonal prophylaxis during community outbreaks 2
- In immunocompromised patients, may continue up to 12 weeks 2
- Should be initiated within 48 hours following close contact with an infected individual 1, 4
Pediatric Patients (≥1 year to 12 years)
Same weight-based doses as treatment, but once daily for 10 days: 1, 5, 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 mg/kg once daily for 10 days 1, 5
- Prophylaxis is not recommended for infants <3 months unless the situation is judged critical due to limited safety data 5
Renal Impairment Adjustments
For creatinine clearance 10-30 mL/min: 3, 1, 5
- Treatment: 75 mg once daily (instead of twice daily) for 5 days
- Prophylaxis: 30 mg once daily for 10 days OR 75 mg every other day for 10 days (5 total doses)
Oseltamivir is not recommended for end-stage renal disease patients not undergoing dialysis. 2
Formulations and Administration
Available Forms
Oral Suspension Dosing Volumes
For the 6 mg/mL suspension: 3, 1, 5
- 30 mg dose = 5 mL
- 45 mg dose = 7.5 mL
- 60 mg dose = 10 mL
- 75 mg dose = 12.5 mL
Administration Tips
- Capsules can be opened and contents mixed with liquid if patient cannot swallow whole 4
- If commercially manufactured suspension is unavailable, pharmacies can compound a suspension based on package label instructions (final concentration 6 mg/mL) 3, 5
- Administration with meals improves gastrointestinal tolerability, as nausea and vomiting are the most common adverse effects 3, 5, 2
Special Populations
Pregnancy
- Same dosing as non-pregnant adults: 75 mg twice daily for 5 days 1
- Oseltamivir is preferred over zanamivir in pregnancy 1, 4
- No contraindication exists for use during any trimester or postpartum period 1
Breastfeeding
- Oseltamivir is not a contraindication to breastfeeding 1
Critical Timing Considerations
The earlier oseltamivir is initiated, the greater the benefit: 6, 7
- Initiation within 12 hours of fever onset reduces illness duration by approximately 3.1 days compared to initiation at 48 hours 6
- Treatment within 24 hours of symptom onset reduces illness duration by 37-40% compared to placebo 7
- While optimal benefit occurs within 48 hours, treatment should not be withheld in high-risk or hospitalized patients presenting beyond this window 1, 4
Drug Interactions
Live Attenuated Influenza Vaccine (LAIV): 1, 5
- Avoid LAIV within 48 hours before oseltamivir use
- Do not use oseltamivir for 14 days after LAIV vaccination unless medically necessary