Tamiflu (Oseltamivir) Dosage and Administration
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; pediatric dosing is weight-based for children ≥12 months and age-based for infants, with treatment initiated within 48 hours of symptom onset for maximum effectiveness. 1, 2
Adult and Adolescent Dosing (≥13 years)
Treatment
Prophylaxis
- 75 mg orally once daily for at least 10 days following close contact with an infected individual 1, 2
- May continue up to 6 weeks during a community outbreak 2
- In immunocompromised patients, may extend up to 12 weeks 2
Pediatric Dosing (≥12 months to 12 years)
Weight-Based Treatment (5 days, twice daily)
- ≤15 kg (≤33 lb): 30 mg twice daily 1, 2
- >15-23 kg (33-51 lb): 45 mg twice daily 1, 2
- >23-40 kg (51-88 lb): 60 mg twice daily 1, 2
- >40 kg (>88 lb): 75 mg twice daily 1, 2
Weight-Based Prophylaxis (10 days, once daily)
Infant Dosing (<12 months)
Ages 9-11 months
- Treatment: 3.5 mg/kg per dose twice daily for 5 days 1
- Prophylaxis: 3.5 mg/kg per dose once daily for 10 days 1
Term Infants 0-8 months
- Treatment: 3 mg/kg per dose twice daily for 5 days 1, 2
- Prophylaxis: 3 mg/kg per dose once daily for infants 3-8 months 1
- Prophylaxis not recommended for infants <3 months unless situation is judged critical due to limited safety data 1
Preterm Infants (Based on Postmenstrual Age)
- <38 weeks postmenstrual age: 1.0 mg/kg twice daily 3, 4
- 38-40 weeks postmenstrual age: 1.5 mg/kg twice daily 3, 4
- >40 weeks postmenstrual age: 3.0 mg/kg twice daily 3, 4
- Preterm infants require lower weight-based dosing due to immature renal function and risk of drug accumulation 1
Renal Impairment Adjustments
Creatinine Clearance 10-30 mL/min
- Treatment: 75 mg once daily for 5 days 1, 3
- Prophylaxis: 30 mg once daily for 10 days OR 75 mg every other day for 10 days (5 total doses) 1, 3
End-Stage Renal Disease
- Oseltamivir is not recommended for patients with end-stage renal disease not undergoing dialysis 2
Formulation and Administration
Available Formulations
Oral Suspension Dosing Volumes
Administration Instructions
- May be taken with or without food, though administration with meals may improve gastrointestinal tolerability 1, 3, 2
- If commercially manufactured oral suspension is unavailable, pharmacies can compound a suspension (final concentration 6 mg/mL) based on package label instructions 1, 3
- Capsules can be opened and contents mixed with liquid for patients who cannot swallow capsules whole 3
Important Clinical Considerations
Timing of Initiation
- Treatment should be initiated within 48 hours of symptom onset for maximum effectiveness 3, 2
- Evidence suggests oseltamivir may increase survival when used within 5 days of symptom onset in H1N1-infected ICU patients 5
Common Adverse Effects
- Nausea and vomiting are the most common adverse events, occurring in approximately 5-15% of patients 3, 6
- Gastrointestinal effects are typically mild and transient 6
- Taking with food significantly reduces these effects 1, 3, 6
Drug Interactions
- Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir administration 3, 4
- Do not use oseltamivir for 14 days after LAIV vaccination 3, 4
Critical Pitfalls to Avoid
- Do not use lower doses or shorter treatment durations than recommended, as this may reduce effectiveness and contribute to viral resistance 7
- Do not delay treatment beyond 48 hours in outpatients or general medicine patients, as benefit diminishes significantly 5
- Do not use standard term infant dosing in preterm infants, as immature renal function can lead to toxic drug concentrations 1