What is the recommended dosing for Tamiflu (oseltamivir) for prophylaxis against influenza A and B?

Prophylactic Tamiflu Dosing

For influenza prophylaxis, oseltamivir (Tamiflu) should be dosed at 75 mg once daily in adults and adolescents ≥13 years, and weight-based once-daily dosing in children ≥1 year, continued for 10 days after household exposure or up to 6 weeks during community outbreaks. 1, 2

Adult and Adolescent Prophylaxis (≥13 years)

• Standard dose: 75 mg orally once daily 1, 2
• Duration:
  • Post-exposure prophylaxis: 10 days following close contact with infected individual 1, 2
  • Seasonal/community outbreak prophylaxis: Up to 6 weeks 1, 2
  • Immunocompromised patients: May extend up to 12 weeks 2
• Can be taken with or without food, though administration with meals may reduce gastrointestinal side effects 3, 2

Pediatric Prophylaxis (≥1 year)

Weight-based once-daily dosing (same weight categories as treatment, but half the frequency): 1, 2

• ≤15 kg: 30 mg once daily (5 mL oral suspension) 1, 2
• >15-23 kg: 45 mg once daily (7.5 mL oral suspension) 1, 2
• >23-40 kg: 60 mg once daily (10 mL oral suspension) 1, 2
• >40 kg: 75 mg once daily (12.5 mL oral suspension) 1, 2

Duration: 10 days post-exposure or up to 6 weeks during community outbreaks 1, 2

Infants (<1 year)

• Prophylaxis is NOT recommended for infants <3 months unless the situation is judged critical due to limited safety data 1, 3
• Ages 3-11 months: 3 mg/kg once daily for 10 days (if prophylaxis deemed necessary) 1, 3

Renal Impairment Adjustments

For patients with creatinine clearance 10-30 mL/min: 1, 3

• Option 1: 30 mg once daily for 10 days
• Option 2: 75 mg every other day for 10 days (total 5 doses)

Oseltamivir is not recommended for end-stage renal disease patients not on dialysis 2

Critical Timing Considerations

• Initiate prophylaxis within 48 hours of exposure to infected individual for maximum effectiveness 1, 2
• Do not delay initiation waiting for laboratory confirmation—start based on clinical suspicion if exposure is documented 4
• Protection lasts only as long as oseltamivir is being taken; it does not provide lasting immunity 2

Common Pitfalls to Avoid

• Do not confuse prophylaxis dosing (once daily) with treatment dosing (twice daily)—this is a frequent prescribing error 4
• Avoid oseltamivir if live attenuated influenza vaccine (LAIV) was given within past 2 weeks, as it may interfere with vaccine efficacy 3
• Do not use oseltamivir within 48 hours before LAIV administration 3
• Prophylaxis is not a substitute for annual influenza vaccination, which remains the primary prevention strategy 2

Formulation Options

• Available as 30 mg, 45 mg, and 75 mg capsules 2
• Oral suspension: 6 mg/mL concentration (preferred for children and those unable to swallow capsules) 2
• Capsules can be opened and mixed with liquid if swallowing is difficult 3

Adverse Effects

• Most common: nausea (12-15%) and vomiting (2.5-3%) 5
• Gastrointestinal effects are mild, transient, and significantly reduced when taken with food 6, 7
• Headache and skin reactions may occur 3

Evidence for Efficacy

Post-exposure prophylaxis demonstrates 58-89% protective efficacy in household contacts when initiated within 48 hours of index case symptom onset 6, 8. Seasonal prophylaxis shows >70% protection against naturally acquired influenza during periods of community activity 6, 5. In vaccinated high-risk elderly patients, adjunctive prophylaxis demonstrates 92% protective efficacy 6.