Normal Tamiflu (Oseltamivir) Dosing
For adults and adolescents ≥13 years, the standard treatment dose is 75 mg orally twice daily for 5 days, and for prophylaxis, 75 mg once daily for 10 days post-exposure. 1, 2, 3
Adult Dosing (≥13 years)
Treatment:
- 75 mg orally twice daily for 5 days (equivalent to 12.5 mL of oral suspension twice daily) 1, 2, 3
- Initiate within 48 hours of symptom onset for maximum benefit 1, 3
- Can be taken with or without food, though taking with food reduces nausea and vomiting 2, 4
Prophylaxis:
- 75 mg once daily for 10 days following close contact with infected individual 1, 2, 3
- For seasonal prophylaxis during community outbreak: 75 mg once daily for up to 6 weeks 3
- In immunocompromised patients: may continue up to 12 weeks 3
Pediatric Dosing (Weight-Based for Children ≥12 months)
Treatment (twice daily for 5 days): 1, 2, 5, 3
- ≤15 kg (≤33 lb): 30 mg twice daily (5 mL oral suspension)
- >15-23 kg (>33-51 lb): 45 mg twice daily (7.5 mL oral suspension)
- >23-40 kg (>51-88 lb): 60 mg twice daily (10 mL oral suspension)
- >40 kg (>88 lb): 75 mg twice daily (12.5 mL oral suspension)
Prophylaxis (once daily for 10 days): 1, 2, 5, 3
- Same weight-based doses as treatment, but once daily instead of twice daily
Infant Dosing (<12 months)
Treatment (twice daily for 5 days): 1, 2, 4, 3
- Infants 9-11 months: 3.5 mg/kg per dose twice daily
- Term infants 0-8 months: 3 mg/kg per dose twice daily
- Infants 3-11 months: 3 mg/kg once daily for 10 days
- Not recommended for infants <3 months unless situation is critical due to limited safety data 1, 2
Preterm Infant Dosing (Based on Postmenstrual Age)
Preterm infants require substantially lower doses due to immature renal function: 1, 2, 4
- <38 weeks postmenstrual age: 1.0 mg/kg twice daily
- 38-40 weeks postmenstrual age: 1.5 mg/kg twice daily
- >40 weeks postmenstrual age: 3.0 mg/kg twice daily
Renal Impairment Adjustments
For creatinine clearance 10-30 mL/min: 1, 2, 4, 3
Treatment:
- 75 mg once daily (instead of twice daily) for 5 days
Prophylaxis:
- 30 mg once daily for 10 days, OR
- 75 mg every other day for 10 days (5 total doses)
Formulation Options
- Capsules: 30 mg, 45 mg, 75 mg
- Oral suspension: 6 mg/mL when reconstituted (preferred for patients who cannot swallow capsules)
- Capsules can be opened and contents mixed with liquid if needed 2
Critical Timing Considerations
- Initiate within 48 hours of symptom onset for optimal benefit
- Treatment after 48 hours may still provide benefit in hospitalized or high-risk patients and should be considered 1
- Initiate within 48 hours following close contact with infected individual
Administration Pearls
To minimize gastrointestinal side effects: 2, 4
- Take with food - significantly reduces nausea and vomiting
- Nausea occurs in ~10% and vomiting in ~9% of adults on treatment 2
- In children, vomiting occurs in 14.3% vs 8.5% on placebo 2
- Only ~1% discontinue due to GI effects 2
Special Populations
Pregnancy: 4
- Same dosing as non-pregnant adults: 75 mg twice daily for 5 days
- No dose adjustment needed throughout all trimesters or postpartum period
- Breastfeeding is not a contraindication 4
Elderly (≥65 years): 2
- Standard adult dose if normal renal function
- Must assess creatinine clearance - dose reduction mandatory if CrCl <60 mL/min
- Age itself does not require dose adjustment; renal function is the key consideration 2
Drug Interactions
Live Attenuated Influenza Vaccine (LAIV): 2, 4
- Avoid LAIV within 48 hours before oseltamivir
- Do not use oseltamivir for 14 days after LAIV vaccination
Common Pitfalls to Avoid
- Do not delay treatment waiting for laboratory confirmation in high-risk patients - rapid antigen tests have poor sensitivity 1, 4
- Do not withhold treatment beyond 48 hours in hospitalized or high-risk patients - some benefit still exists 1
- Always verify current weight in children to avoid dosing errors 5
- Always assess renal function in elderly patients before prescribing 2
- Use appropriate measuring device for oral suspension - provide device that accurately measures mL 3