Tamiflu (Oseltamivir) Dosing Guidelines
Adult and Adolescent Dosing (≥13 years)
For adults and adolescents with normal renal function, the standard treatment dose is 75 mg orally twice daily for 5 days, and prophylaxis is 75 mg once daily for 10 days. 1, 2
Treatment Regimen
- 75 mg twice daily for 5 days for influenza treatment 1, 2
- Initiate within 48 hours of symptom onset for maximum benefit (reduces illness duration by 1-1.5 days) 1, 2
- Can be taken with or without food, though administration with meals significantly reduces nausea and vomiting 1, 3
Prophylaxis Regimen
- 75 mg once daily for 10 days following close contact with infected individual 1, 4
- Up to 6 weeks for community outbreak (seasonal prophylaxis) 4
- Start within 48 hours of exposure 1
Pediatric Dosing (≥1 year to 12 years)
Weight-based dosing is mandatory for children, with doses ranging from 30 mg to 75 mg twice daily for treatment and once daily for prophylaxis. 1, 3
Treatment Dosing (5 days, twice daily)
- ≤15 kg (≤33 lb): 30 mg twice daily 1, 3
- >15-23 kg (>33-51 lb): 45 mg twice daily 1, 3
- >23-40 kg (>51-88 lb): 60 mg twice daily 1, 3
- >40 kg (>88 lb): 75 mg twice daily 1, 3
Prophylaxis Dosing (10 days, once daily)
Infant Dosing (<1 year)
Infants require age-based mg/kg dosing, NOT the weight-based unit doses used for older children. 1, 3
Term Infants (≥37 weeks gestation at birth)
- 9-11 months: 3.5 mg/kg per dose twice daily for 5 days 1, 3
- 0-8 months: 3 mg/kg per dose twice daily for 5 days 1, 3, 4
- For prophylaxis in infants 3-11 months: 3 mg/kg once daily for 10 days 1, 3
- Prophylaxis NOT recommended for infants <3 months unless situation is critical due to limited safety data 1, 3
Preterm Infants (Critical Distinction)
Never use term infant dosing for preterm infants—they require substantially lower doses based on postmenstrual age (gestational age + chronological age) due to immature renal function. 1, 3
- <38 weeks postmenstrual age: 1.0 mg/kg twice daily 1, 3
- 38-40 weeks postmenstrual age: 1.5 mg/kg twice daily 1, 3
- >40 weeks postmenstrual age: 3.0 mg/kg twice daily 1, 3
Renal Impairment Dosing Adjustments
Dose reductions are mandatory when creatinine clearance falls below 60 mL/min to prevent drug accumulation and toxicity. 1, 2, 4
Treatment Dosing Adjustments
- CrCl >60-90 mL/min: 75 mg twice daily (standard dose) 4
- CrCl >30-60 mL/min: 30 mg twice daily for 5 days 4
- CrCl 10-30 mL/min: 75 mg once daily for 5 days OR 30 mg once daily for 5 days 1, 4
- ESRD on hemodialysis: 30 mg immediately, then 30 mg after each hemodialysis cycle (not to exceed 5 days) 4
- ESRD on CAPD: Single 30 mg dose 4
- ESRD not on dialysis: NOT recommended 4
Prophylaxis Dosing Adjustments
- CrCl >60-90 mL/min: 75 mg once daily 4
- CrCl >30-60 mL/min: 30 mg once daily 4
- CrCl 10-30 mL/min: 30 mg once daily OR 75 mg every other day for 10 days (5 total doses) 1, 4
- ESRD on hemodialysis: 30 mg immediately, then 30 mg after alternate hemodialysis cycles 4
- ESRD on CAPD: 30 mg immediately, then 30 mg once weekly 4
Pediatric Renal Impairment
For children with CrCl 10-30 mL/min, reduce the weight-based dose to once daily (instead of twice daily) for treatment. 3 For prophylaxis, give half the standard once-daily dose daily, or the full once-daily dose every other day for 10 days. 3
Formulation and Administration
Available Formulations
Oral Suspension Volumes
Storage After Reconstitution
Administration Tips
- Capsules can be opened and mixed with liquid if patient cannot swallow whole 1
- If commercial suspension unavailable, pharmacies can compound using package insert instructions to achieve 6 mg/mL concentration 1
- For infants <1 year, use appropriate measuring device (3 mL or 5 mL oral syringe) instead of standard syringe 2
Special Populations
Elderly Patients (≥65 years)
Standard adult dosing (75 mg twice daily) applies if renal function is normal, but dose reductions are mandatory when CrCl falls below 60 mL/min. 1, 2 Age alone does not require dose adjustment—assess renal function as it declines with aging. 1
Pregnancy and Breastfeeding
Pregnant women receive the same dosing as non-pregnant adults: 75 mg twice daily for 5 days. 2 Breastfeeding is not a contraindication to oseltamivir use. 2
Critical Pitfalls to Avoid
Common Dosing Errors
- Never use weight-based unit doses (30,45,60,75 mg) for infants <1 year—these are too high; use mg/kg dosing instead 3
- Never use term infant dosing (3 mg/kg) for preterm infants—leads to toxic concentrations due to immature renal function 2
- Do not confuse treatment dosing (twice daily) with prophylaxis dosing (once daily)—can lead to underdosing treatment or overdosing prophylaxis 1
- Do not confuse GFR with creatinine clearance when calculating renal dosing 3
Timing Considerations
- Treatment must be initiated within 48 hours of symptom onset for maximum effectiveness 1, 2
- Prophylaxis should start within 48 hours of exposure to infected individuals 1
- Starting treatment >48 hours after symptom onset shows minimal benefit in most populations 5
Adverse Effects and Tolerability
Gastrointestinal Effects
- Nausea and vomiting are most common adverse effects, occurring in approximately 10-15% of patients 1, 2
- Taking oseltamivir with food significantly reduces GI side effects 1, 3, 2
- Only approximately 1% of patients discontinue due to GI effects 1
- In children, vomiting occurs in 14.3% vs 8.5% with placebo 1
Serious Reactions
- Anaphylaxis and serious skin reactions (toxic epidermal necrolysis, Stevens-Johnson Syndrome, erythema multiforme) reported in postmarketing surveillance 4
- Stop oseltamivir immediately if allergic-like reaction occurs 4
Drug Interactions
Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir use, and do not use oseltamivir for 14 days after LAIV vaccination. 1 This prevents interference with vaccine efficacy.