Oseltamivir (Tamiflu) Dosing Guidelines
For adults and adolescents ≥13 years, the standard treatment dose is 75 mg orally twice daily for 5 days, and prophylaxis is 75 mg once daily for 10 days; pediatric dosing is weight-based for children ≥12 months and mg/kg-based for infants, with mandatory dose reductions required for renal impairment (creatinine clearance <60 mL/min). 1, 2, 3
Adult and Adolescent Dosing (≥13 years)
Treatment Regimen
- Standard dose: 75 mg orally twice daily for 5 days 1, 4, 3
- Timing: Initiate within 48 hours of symptom onset for maximum benefit, though treatment should not be withheld in high-risk or hospitalized patients presenting beyond 48 hours 1, 4
- Clinical benefit: Reduces illness duration by 1–1.5 days (24–36 hours) when started early 2, 5
- Earlier initiation yields greater benefit: Treatment within 12 hours reduces illness duration by an additional 74.6 hours compared to treatment at 48 hours 6
Prophylaxis Regimen
- Post-exposure prophylaxis: 75 mg once daily for 10 days, started within 48 hours of exposure 1, 2, 3
- Community outbreak: 75 mg once daily for up to 6 weeks 3
Pediatric Weight-Based Dosing (Children 1–12 years)
Treatment (twice daily for 5 days)
- ≤15 kg (≤33 lb): 30 mg twice daily 1, 2, 4
- >15–23 kg (>33–51 lb): 45 mg twice daily 1, 2, 4
- >23–40 kg (>51–88 lb): 60 mg twice daily 1, 2, 4
- >40 kg (>88 lb): 75 mg twice daily 1, 2, 4
Prophylaxis (once daily for 10 days)
- Same weight-based doses as treatment, but administered once daily instead of twice daily 1, 2
- For community outbreak: same doses once daily for up to 6 weeks 3
Infant Dosing (<12 months)
Term Infants (Treatment, twice daily for 5 days)
- 9–11 months: 3.5 mg/kg per dose twice daily 1, 2
- 0–8 months: 3 mg/kg per dose twice daily 1, 2, 3
- FDA approval: Oseltamivir is approved for treatment starting at 2 weeks of age 1, 2
Preterm Infants (Postmenstrual Age-Based Dosing)
Critical: Do not use term infant dosing for preterm infants—this leads to toxic drug concentrations due to immature renal function 1, 2, 7
- <38 weeks postmenstrual age: 1.0 mg/kg twice daily 1, 2
- 38–40 weeks postmenstrual age: 1.5 mg/kg twice daily 1, 2
- >40 weeks postmenstrual age: 3.0 mg/kg twice daily 1, 2
Infant Prophylaxis
- 3–11 months: 3 mg/kg once daily for 10 days 1, 2
- <3 months: Prophylaxis not recommended unless situation is judged critical, due to limited safety data 1, 2
Renal Impairment Dose Adjustments
Treatment Dosing (5-day course)
| Creatinine Clearance | Adjusted Dose |
|---|---|
| >30–60 mL/min | 30 mg twice daily [4,3] |
| 10–30 mL/min | 30 mg once daily [1,2,4,3] |
| ESRD on hemodialysis | 30 mg immediately, then 30 mg after each dialysis session (max 5 days) [4,3] |
| ESRD on CAPD | Single 30 mg dose immediately [4,3] |
| ESRD not on dialysis | Not recommended [1,3] |
Prophylaxis Dosing
| Creatinine Clearance | Adjusted Dose |
|---|---|
| >30–60 mL/min | 30 mg once daily [4,3] |
| 10–30 mL/min | 30 mg every other day OR 75 mg every other day (5 total doses over 10 days) [1,2,3] |
| ESRD on hemodialysis | 30 mg immediately, then 30 mg after alternate hemodialysis cycles [3] |
| ESRD on CAPD | 30 mg immediately, then 30 mg once weekly [3] |
Formulation and Administration
Available Formulations
- Capsules: 30 mg, 45 mg, 75 mg 1, 2, 3
- Oral suspension: 6 mg/mL when reconstituted from powder 1, 2, 3
Suspension Dosing Volumes (6 mg/mL concentration)
Administration Guidance
- Can be taken with or without food, though administration with meals significantly reduces gastrointestinal side effects (nausea/vomiting) 1, 2, 7, 6
- For infants: Use a calibrated 3 mL or 5 mL oral syringe for accurate measurement; do not use household spoons or the standard syringe supplied with the product 2
- If commercial suspension unavailable: Pharmacies can compound a 6 mg/mL suspension according to package insert instructions, or capsules can be opened and mixed with sweetened liquid 1, 2
Special Populations
Elderly Patients (≥65 years)
- No dose reduction required based on age alone; standard adult dosing (75 mg twice daily) applies 4, 7
- However: Renal function must be assessed, as dose reductions are mandatory when creatinine clearance falls below 60 mL/min 2, 7
Pregnant and Breastfeeding Women
- Same dosing as non-pregnant adults: 75 mg twice daily for 5 days 4, 7
- Breastfeeding is not a contraindication to oseltamivir use 7
Immunocompromised Patients
- Standard dosing applies 4
- Treatment should be initiated regardless of time elapsed since symptom onset in immunocompromised patients or those unable to mount adequate febrile response 4
High-Risk Groups Requiring Treatment
Treat these patients even if presenting beyond 48 hours: 4
- Hospitalized patients with severe or progressive influenza
- Children <2 years
- Adults ≥65 years
- Pregnant women
- Individuals with chronic cardiac or respiratory disease
- Immunocompromised patients
Critical Timing Considerations
- Treatment: Initiate within 48 hours of symptom onset for maximum benefit; earlier initiation (≤36 hours) yields faster symptom resolution 1, 2, 4, 6, 5
- Prophylaxis: Start within 48 hours of exposure to infected individuals 2, 7
- Complete the full 5-day course even if symptoms improve earlier; stopping early may promote resistance 2
Common Pitfalls and Caveats
Dosing Errors to Avoid
- Do not confuse treatment (twice daily) with prophylaxis (once daily) dosing—this leads to underdosing treatment or overdosing prophylaxis 4, 7
- Do not use weight-based categorical dosing (≤15 kg = 30 mg) for infants <12 months; that scheme applies only to children ≥12 months 2
- Do not apply term-infant dosing to preterm infants; postmenstrual age-based dosing is required to avoid toxicity 1, 2, 7
Adverse Effects Management
- Gastrointestinal effects (nausea, vomiting, diarrhea) occur in 10–15% of patients 2, 6, 8
- Taking with food significantly reduces these effects; symptoms are typically mild, transient, and resolve within 1–2 days 1, 2, 6
- Only ~1% of patients discontinue due to GI side effects 2
Drug Interactions
- Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir use 2, 3
- Do not use oseltamivir for 14 days after LAIV vaccination unless medically indicated 2