Oseltamivir for Post-Exposure Prophylaxis of Influenza
Yes, oseltamivir (Tamiflu) is highly effective for post-exposure prophylaxis of influenza and should be initiated as soon as possible—ideally within 48 hours of exposure—at a dose of 75 mg once daily for 10 days in healthy adults. 1
Standard Dosing for Healthy Adults
- 75 mg orally once daily for 10 days following close contact with a confirmed or suspected influenza case. 2, 1, 3
- Initiate prophylaxis within 48 hours of exposure for maximum protective benefit. 1
- If more than 48 hours have elapsed since exposure, do not start prophylaxis; instead, educate the patient to begin full treatment dosing (75 mg twice daily) immediately if symptoms develop. 1
Clinical Efficacy
- Oseltamivir prophylaxis reduces the risk of laboratory-confirmed influenza by 74–82% during community outbreaks in otherwise healthy adults. 1
- In household-contact studies where prophylaxis is started within 48 hours, protective efficacy ranges from 58% to 89%. 1, 4
- A randomized controlled trial demonstrated 89% protective efficacy for individuals and 84% for households when oseltamivir was given to contacts of influenza-positive index cases. 4
- Protection persists only while the medication is taken; once the 10-day course is stopped, susceptibility to influenza returns. 1
High-Priority Populations for Prophylaxis
- Severely immunocompromised patients (e.g., hematopoietic stem cell transplant recipients, organ transplant recipients) should receive prophylaxis after household exposure, particularly when vaccination is contraindicated or expected to have low effectiveness. 1
- Unvaccinated healthcare workers with frequent contact with high-risk patients during an outbreak. 1
- Unvaccinated household contacts of persons at very high risk of complications (e.g., infants <6 months, elderly, immunocompromised individuals). 1
- Adults at high risk for complications who are within 2 weeks of receiving influenza vaccination—before optimal immunity has developed. 1
- Residents of long-term care facilities during institutional outbreaks; all eligible residents should receive prophylaxis regardless of vaccination status, continued for ≥2 weeks or until 1 week after the outbreak ends. 1
Renal Dosing Adjustments
- Creatinine clearance 10–30 mL/min: reduce prophylaxis dose to 30 mg once daily for 10 days or 75 mg every other day for 10 days (5 total doses). 2, 1, 3
- No dose adjustment is required solely on the basis of age for patients ≥65 years; standard dosing applies. 1
Extended Prophylaxis in Special Populations
- Severely immunocompromised patients may continue oseltamivir prophylaxis for up to 12 weeks during community outbreaks. 1, 3
Administration and Tolerability
- Oseltamivir may be taken with or without food, but taking it with meals significantly reduces nausea and vomiting, the most common adverse effects (occurring in ~10% of patients). 2, 5, 6
- Gastrointestinal effects are mild, transient, and rarely lead to discontinuation (~1% of patients). 2
Critical Caveats
- Oseltamivir prophylaxis is not a substitute for annual influenza vaccination, which remains the primary prevention strategy. 1
- Live attenuated influenza vaccine (LAIV) should not be administered within 48 hours before or 2 weeks after oseltamivir use, as concurrent oseltamivir can diminish LAIV effectiveness. 2, 1
- If symptoms develop during prophylaxis, switch to treatment dosing (75 mg twice daily for 5 days) and consider testing for influenza. 1
- Do not use prophylaxis routinely or for widespread use outside institutional outbreaks; reserve it for high-risk exposures to avoid resistance. 1, 7
Alternative Agent: Zanamivir
- Zanamivir 10 mg (two 5-mg inhalations) once daily for 7–10 days is an alternative for patients ≥5 years when oseltamivir resistance is suspected or when compliance with oral medication is a concern. 1
- Zanamivir may provoke bronchospasm in patients with asthma or COPD and should be avoided in these populations. 1
Practical Algorithm for Post-Exposure Prophylaxis
| Clinical Scenario | Recommended Action |
|---|---|
| Healthy adult exposed to confirmed influenza within 48 hours | Start oseltamivir 75 mg once daily for 10 days [1] |
| Exposure occurred >48 hours ago | Do not start prophylaxis; educate patient to begin treatment (75 mg twice daily) if symptoms develop [1] |
| Severely immunocompromised patient exposed to influenza | Start oseltamivir 75 mg once daily; may extend up to 12 weeks during outbreaks [1] |
| Unvaccinated healthcare worker during outbreak | Start oseltamivir 75 mg once daily for duration of outbreak (up to 6 weeks) [1] |
| Patient with CrCl 10–30 mL/min | Reduce dose to 30 mg once daily or 75 mg every other day [2,1] |
| Patient develops symptoms during prophylaxis | Switch to treatment dosing (75 mg twice daily for 5 days) [1] |