Oseltamivir (Tamiflu) Dosing
For adults and adolescents ≥13 years, the standard dose is 75 mg orally twice daily for 5 days for treatment, or 75 mg once daily for prophylaxis. 1, 2
Treatment Dosing
Adults and Adolescents (≥13 years)
- 75 mg orally twice daily for 5 days 1, 2
- Initiate within 48 hours of symptom onset for maximum effectiveness 3, 2
- Can be taken with or without food, though administration with meals may reduce gastrointestinal side effects 3, 2
Pediatric Patients (≥12 months)
Weight-based dosing twice daily for 5 days: 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
- 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): 1, 3
- <38 weeks: 1.0 mg/kg twice daily for 5 days
- 38-40 weeks: 1.5 mg/kg twice daily for 5 days
- >40 weeks: 3.0 mg/kg twice daily for 5 days
Prophylaxis Dosing
Adults and Adolescents (≥13 years)
- 75 mg once daily for 10 days (post-exposure prophylaxis) 1, 2
- 75 mg once daily for up to 6 weeks (seasonal prophylaxis during community outbreak) 2
- Up to 12 weeks in immunocompromised patients 2
Pediatric Patients (≥1 year)
- Same weight-based doses as treatment, but once daily instead of twice daily for 10 days 1, 2
- Seasonal prophylaxis can be extended up to 6 weeks during community outbreaks 2
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 3
Renal Impairment Adjustments
For creatinine clearance 10-30 mL/min: 1, 3, 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)
Available Formulations
- Capsules: 30 mg, 45 mg, 75 mg 1, 2
- Oral suspension: 6 mg/mL when reconstituted 1, 2
- Suspension dosing volumes: 30 mg = 5 mL, 45 mg = 7.5 mL, 60 mg = 10 mL, 75 mg = 12.5 mL 1
Special Populations
Pregnancy
- Pregnant women receive the same dosing as non-pregnant adults: 75 mg twice daily for 5 days 1
- No dose adjustment needed across all trimesters or postpartum period 1
Breastfeeding
- Oseltamivir is compatible with breastfeeding and is not a reason to discontinue 1
Important Clinical Pearls
- Capsules can be opened and mixed with liquid if patient cannot swallow whole 3
- Common adverse effects include nausea and vomiting (5-15% of patients), which are typically mild, transient, and reduced when taken with food 3, 4
- Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir, and do not use oseltamivir for 14 days after LAIV vaccination 1, 3
- Treatment should not be withheld while awaiting laboratory confirmation in high-risk patients with suspected influenza 3