Tamiflu Post-Exposure Prophylaxis Dosing
For post-exposure prophylaxis after influenza exposure, adults and adolescents ≥13 years should receive oseltamivir 75 mg once daily for 10 days, initiated within 48 hours of close contact with an infected individual. 1, 2, 3
Adult and Adolescent Dosing (≥13 years)
- Standard prophylaxis dose: 75 mg orally once daily for 10 days following close contact with a confirmed or suspected influenza case 1, 2, 3
- Initiation must occur within 48 hours of exposure for maximum effectiveness 1, 2
- For seasonal prophylaxis during community outbreaks, the same dose can be continued for up to 6 weeks 2, 3
- In immunocompromised patients, prophylaxis may be extended up to 12 weeks 2, 3
Pediatric Dosing (1-12 years)
Weight-based dosing once daily for 10 days: 1, 2, 3
- ≤15 kg: 30 mg (5 mL oral suspension) once daily
15-23 kg: 45 mg (7.5 mL oral suspension) once daily
23-40 kg: 60 mg (10 mL oral suspension) once daily
40 kg: 75 mg (12.5 mL oral suspension) once daily
Infants (3-11 months)
- 3 mg/kg once daily for 10 days 2, 4, 3
- Prophylaxis is not recommended for infants <3 months unless the situation is judged critical due to limited safety data 4, 3
Renal Impairment Adjustments
For patients with creatinine clearance 10-30 mL/min: 1, 2, 4, 3
- Reduce dose to 30 mg once daily for 10 days, OR
- Alternative: 75 mg every other day for 10 days (5 total doses)
Administration Considerations
- May be taken with or without food, though administration with food improves gastrointestinal tolerability 4, 3
- Oral suspension is the preferred formulation for patients who cannot swallow capsules 1, 3
- Capsules can be opened and mixed with liquid if needed 4
Clinical Efficacy Evidence
- In prophylaxis trials, oseltamivir reduced symptomatic influenza risk by 3.05% absolute risk reduction (NNT = 33) in individuals and 13.6% (NNT = 7) in household contacts 5
- A study in vaccinated frail elderly residents demonstrated 92% protective efficacy when oseltamivir 75 mg once daily was used for 6 weeks during a community outbreak 6
- Prophylaxis provides 67-74% protective efficacy against laboratory-confirmed influenza when used for 4-6 weeks 7
Important Safety Considerations
Common adverse effects during prophylaxis: 5
- Headaches (3.15% increased risk; NNTH = 32)
- Nausea (4.15% increased risk; NNTH = 25)
- Psychiatric adverse events (1.06% increased risk; NNTH = 94)
- Renal events (0.67% increased risk)
Critical Timing and Pitfalls
- Do not delay initiation - prophylaxis must begin within 48 hours of exposure for optimal benefit 1, 2, 3
- Prophylaxis is not a substitute for vaccination but serves as an adjunct in high-risk situations 8, 9
- The protective effect lasts only as long as oseltamivir is being taken 2, 3
- Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir use, and do not use oseltamivir for 14 days after LAIV vaccination 2, 4