Tamiflu (Oseltamivir) Weight-Based Dosing Chart
For treatment of influenza, oseltamivir dosing is weight-based in children and fixed-dose in adults, with critical adjustments required for renal impairment and preterm infants to avoid toxicity or therapeutic failure. 1, 2
Adult and Adolescent Dosing (≥13 years)
Treatment: 75 mg orally twice daily for 5 days 3, 1, 2
- Must be initiated within 48 hours of symptom onset for maximum benefit 1, 4
- Can be taken with or without food, though administration with meals significantly reduces nausea and vomiting 3, 1, 4
Prophylaxis: 75 mg orally once daily for 10 days (post-exposure) or up to 6 weeks (community outbreak) 1, 2
Pediatric Dosing (≥1 year to 12 years) - Weight-Based
Treatment (twice daily for 5 days): 3, 1, 2
- ≤15 kg (≤33 lb): 30 mg twice daily
- >15-23 kg (>33-51 lb): 45 mg twice daily
- >23-40 kg (>51-88 lb): 60 mg twice daily
- >40 kg (>88 lb): 75 mg twice daily
Prophylaxis (once daily for 10 days): 1, 2
- ≤15 kg: 30 mg once daily
- >15-23 kg: 45 mg once daily
- >23-40 kg: 60 mg once daily
- >40 kg: 75 mg once daily
Infant Dosing (<1 year) - Age-Based
Term Infants (Treatment): 3, 1, 2
- 9-11 months: 3.5 mg/kg per dose twice daily for 5 days
- 0-8 months: 3.0 mg/kg per dose twice daily for 5 days
Prophylaxis (3-11 months): 3.0 mg/kg once daily for 10 days 1, 2
- Prophylaxis NOT recommended for infants <3 months unless situation is critical due to limited safety data 1
Preterm Infant Dosing - Postmenstrual Age-Based
CRITICAL: Preterm infants require substantially lower doses than term infants due to immature renal function; using term infant dosing leads to toxic drug accumulation 3, 1, 5
Dosing based on postmenstrual age (gestational age + chronological age): 3, 1, 5
- <38 weeks postmenstrual age: 1.0 mg/kg per dose twice daily
- 38-40 weeks postmenstrual age: 1.5 mg/kg per dose twice daily
- >40 weeks postmenstrual age: 3.0 mg/kg per dose twice daily
- For extremely preterm infants (<28 weeks), consult pediatric infectious diseases 3
Renal Impairment Dosing Adjustments
Dose reductions are MANDATORY when creatinine clearance falls below 60 mL/min 1, 4, 2
Treatment Dosing: 3, 1, 2
- CrCl >60-90 mL/min: 75 mg twice daily for 5 days (no adjustment)
- CrCl >30-60 mL/min: 30 mg twice daily for 5 days
- CrCl >10-30 mL/min: 30 mg once daily for 5 days OR 75 mg once daily for 5 days
- CrCl ≤10 mL/min (not on dialysis): NOT recommended
Prophylaxis Dosing: 3, 1, 2
- CrCl >60-90 mL/min: 75 mg once daily (no adjustment)
- CrCl >30-60 mL/min: 30 mg once daily
- CrCl >10-30 mL/min: 30 mg once daily OR 75 mg every other day for 10 days (5 total doses)
Pediatric Renal Impairment: 5
- CrCl 10-30 mL/min: Reduce the child's weight-based dose to once daily (instead of twice daily) for treatment
- For prophylaxis: Give half the standard once-daily dose daily, OR give full once-daily dose every other day
Oral Suspension Formulation (6 mg/mL)
Volume conversions for oral suspension: 3, 1, 2
- 30 mg dose = 5 mL
- 45 mg dose = 7.5 mL
- 60 mg dose = 10 mL
- 75 mg dose = 12.5 mL
Preparation: 2
- Commercially manufactured suspension provides 6 mg/mL concentration after reconstitution
- If commercial suspension unavailable, pharmacies can compound suspension per package insert instructions (final concentration also 6 mg/mL) 3, 1
- Capsules can be opened and contents mixed with liquid for patients unable to swallow capsules 1
Critical Pitfalls to Avoid
DO NOT use term infant dosing (3 mg/kg) for preterm infants - this causes toxic drug concentrations due to immature renal function 1, 4
DO NOT confuse GFR with creatinine clearance when calculating renal dosing adjustments 5
DO NOT confuse treatment dosing (twice daily) with prophylaxis dosing (once daily) - this leads to underdosing treatment or overdosing prophylaxis 4
DO NOT delay treatment beyond 48 hours of symptom onset - efficacy decreases significantly after this window 1, 4, 6
DO NOT forget to assess renal function in elderly patients (≥65 years) - age alone doesn't require dose adjustment, but renal function declines with aging and dose reductions are mandatory when CrCl <60 mL/min 1, 4
Special Populations
Pregnancy: Standard adult dosing (75 mg twice daily); no contraindication to use 4
Breastfeeding: Not a contraindication to oseltamivir use 4
Immunocompromised patients: May continue prophylaxis for up to 12 weeks during community outbreak 2