Tamiflu (Oseltamivir) Dosing Recommendations
For adults and adolescents ≥13 years, the standard treatment dose is 75 mg orally twice daily for 5 days, and prophylaxis is 75 mg once daily for 10 days post-exposure or up to 6 weeks during community outbreaks. 1, 2, 3
Treatment Dosing
Adults and Adolescents (≥13 years)
- 75 mg orally twice daily for 5 days 1, 2, 3
- Initiate treatment within 48 hours of symptom onset for maximum effectiveness 2, 4
- Earlier initiation provides greater benefit—starting within 12 hours of fever onset reduces illness duration by 3.1 days more than starting at 48 hours 4
Pediatric Patients (≥12 months to 12 years)
Weight-based dosing twice daily for 5 days: 1, 2, 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 (0-11 months)
- 9-11 months: 3.5 mg/kg per dose twice daily for 5 days 1, 2
- Term infants 0-8 months: 3 mg/kg per dose twice daily for 5 days 1, 2
Preterm Infants
Dosing based on postmenstrual age (gestational age + chronological age), twice daily for 5 days: 1, 2
- <38 weeks: 1.0 mg/kg per dose
- 38-40 weeks: 1.5 mg/kg per dose
- >40 weeks: 3.0 mg/kg per dose
Prophylaxis Dosing
Adults and Adolescents (≥13 years)
- 75 mg once daily for 10 days (post-exposure prophylaxis) 1, 3
- 75 mg once daily for up to 6 weeks (seasonal/community outbreak prophylaxis) 1, 3
- Up to 12 weeks in immunocompromised patients 3
Pediatric Patients (≥1 year to 12 years)
Use the 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 mg/kg once daily for 10 days 1, 2
- Prophylaxis is not recommended for infants <3 months unless the situation is judged critical due to limited safety data 2
Renal Impairment Adjustments
For creatinine clearance 10-30 mL/min: 1, 2
- Treatment: 75 mg once 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 patients with end-stage renal disease not undergoing dialysis 3
Formulation and Administration
Available Forms
Suspension Dosing Volumes
Administration Tips
- Can be taken with or without food, but taking with food improves gastrointestinal tolerability 2, 3, 5
- Capsules can be opened and contents mixed with liquid if patients cannot swallow capsules whole 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 2
Special Populations
Pregnancy
- Pregnant women receive the same dosing as non-pregnant persons: 75 mg twice daily for 5 days 1
- This applies throughout all trimesters and postpartum period (within 2 weeks after delivery) 1
- Oseltamivir is preferred over zanamivir in pregnancy 1
Breastfeeding
- Breastfeeding mothers can receive oseltamivir and should continue breastfeeding 1
Important Drug Interactions
Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir, and do not use oseltamivir for 14 days after LAIV vaccination 1, 2
Common Adverse Effects
- Nausea and vomiting are the most common adverse events (5-15% of patients) 2, 5
- Gastrointestinal effects are typically mild, transient, and occur primarily with first dosing 5, 4
- Other adverse events include headache, diarrhea, and skin reactions 2
- Overall discontinuation rate is low (1.8%) 4
Clinical Pearls
- Treatment reduces illness duration by approximately 1-1.5 days (19-30% reduction) when started within 48 hours 6, 7
- Earlier treatment provides progressively greater benefit—every hour counts 4
- Oseltamivir reduces severity of symptoms by up to 38%, decreases secondary complications, and reduces antibiotic use 5, 6
- Effective against both influenza A and B viruses 5, 6
- Prophylaxis provides >70% protection in unvaccinated adults and 92% protection in vaccinated high-risk elderly patients 5