Oseltamivir (Tamiflu) Prophylaxis Dosing
For influenza prophylaxis, administer oseltamivir 75 mg orally once daily for at least 10 days following close contact with an infected individual, or up to 6 weeks during a community outbreak. 1
Adult and Adolescent Dosing (≥13 years)
- The standard prophylactic dose is 75 mg orally once daily 2, 3, 1
- Duration varies by exposure type:
- Post-exposure prophylaxis: 10 days following close contact with an infected individual 1
- Seasonal/community outbreak prophylaxis: Up to 6 weeks during a community outbreak 3, 1
- Institutional outbreak (e.g., retirement homes): Continue for at least 2 weeks and up to 6 weeks, or approximately 1 week after the last case is identified 3
- Immunocompromised patients: May continue prophylaxis for up to 12 weeks 1
Pediatric Dosing (1-12 years)
- Weight-based dosing once daily (same weight-based doses as treatment, but once daily instead of twice daily): 2, 1
- ≤15 kg (≤33 lb): 30 mg once daily
15-23 kg (>33-51 lb): 45 mg once daily
23-40 kg (>51-88 lb): 60 mg once daily
40 kg (>88 lb): 75 mg once daily
- Duration: 10 days following close contact or up to 6 weeks during community outbreak 1
Infants (3-11 months)
- Dose: 3 mg/kg once daily for 10 days 2
- Important caveat: 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: 2
- 30 mg once daily for 10 days after exposure, OR
- 75 mg once every other day for 10 days (total of 5 doses)
Administration Considerations
- Can be taken with or without food, though taking with meals may reduce gastrointestinal side effects (nausea and vomiting occur in approximately 5-15% of patients) 2, 3
- Available formulations: 30 mg, 45 mg, and 75 mg capsules; oral suspension at 6 mg/mL concentration 2
- Capsules can be opened and mixed with liquid if patients cannot swallow them whole 2
Critical Timing and Vaccine Interactions
- Initiate prophylaxis within 48 hours of exposure for post-exposure prophylaxis 1
- Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir use, and do not use oseltamivir for 14 days after LAIV vaccination 2, 3
- Protection lasts only as long as dosing is continued 1
Common Pitfalls to Avoid
- Do not confuse prophylaxis dosing (once daily) with treatment dosing (twice daily) 2, 1
- In institutional outbreaks, continue surveillance for new cases to determine appropriate duration—do not stop prematurely at 2 weeks if cases continue 3
- For unvaccinated healthcare workers or high-risk contacts, prophylaxis should be considered regardless of vaccination status if outbreak strain is not well-matched to vaccine 3