Adult Tamiflu Prophylaxis Dosing
The recommended dose of oseltamivir (Tamiflu) for adult prophylaxis is 75 mg orally once daily, initiated within 48 hours of exposure to an infected individual and continued for at least 10 days post-exposure or up to 6 weeks during a community outbreak. 1, 2
Standard Prophylaxis Regimen
Adults and adolescents ≥13 years should receive 75 mg once daily for post-exposure prophylaxis, which should be started within 48 hours following close contact with a confirmed or suspected influenza case 1, 3, 4
The duration is 10 days for post-exposure prophylaxis (household or close contact setting) and up to 6 weeks for seasonal/community outbreak prophylaxis 1, 2
For immunocompromised patients, prophylaxis may be extended up to 12 weeks during community outbreaks 1, 3
Formulation and Administration
Oseltamivir is available as 75 mg capsules or oral suspension (6 mg/mL concentration = 12.5 mL per 75 mg dose) 1, 3
The medication can be taken with or without food, though administration with meals may reduce gastrointestinal side effects such as nausea and vomiting 1, 2, 3
If capsules cannot be swallowed, they can be opened and mixed with liquid, or the oral suspension formulation can be used 3
Renal Impairment Adjustments
For creatinine clearance 10-30 mL/min (moderate to severe renal impairment): reduce dose to 30 mg once daily for 10 days OR 75 mg every other day for 10 days (5 total doses) 1, 3, 4
No dose adjustment is required for mild renal impairment (creatinine clearance >30 mL/min) 1
Oseltamivir is not recommended for end-stage renal disease patients not on dialysis 3
Critical Clinical Pearls and Pitfalls
Do not confuse prophylaxis dosing (75 mg once daily) with treatment dosing (75 mg twice daily) - this is a common prescribing error that can lead to underdosing for treatment or unnecessary side effects/cost for prophylaxis 2
Do not delay initiation waiting for laboratory confirmation of influenza in the index case - start prophylaxis based on clinical suspicion if within the 48-hour window from exposure 2
Avoid oseltamivir if the patient received live attenuated influenza vaccine (LAIV) within the past 2 weeks, as the antiviral may interfere with vaccine efficacy; similarly, avoid LAIV within 48 hours before or for 14 days after oseltamivir use 3
The protective efficacy of oseltamivir prophylaxis ranges from 67-74% for laboratory-confirmed influenza when used during community outbreaks 5, 6
Protection lasts only as long as dosing is continued - there is no residual protective effect after discontinuation 1
Efficacy Data
Seasonal prophylaxis with 75 mg once daily for 6 weeks during periods of local influenza activity demonstrated >70% protective efficacy in preventing naturally acquired influenza in unvaccinated healthy adults 5
Post-exposure prophylaxis with 75 mg once daily for 7 days significantly reduced the risk of illness in household contacts when administered within 48 hours of symptom onset in the infected person 5
When used adjunctively in previously vaccinated high-risk elderly patients, oseltamivir demonstrated 92% protective efficacy 5