What is the recommended dosing of Tamiflu (oseltamivir) for adults and children with normal renal function and without significant medical history, such as impaired renal function or pregnancy?

Tamiflu (Oseltamivir) Dosing

For adults and adolescents ≥13 years with normal renal function, the standard treatment dose is 75 mg orally twice daily for 5 days, and for prophylaxis, 75 mg once daily for 10 days. 1, 2

Adult and Adolescent Dosing (≥13 years)

Treatment Regimen:

• 75 mg orally twice daily for 5 days 1, 2
• Initiate within 48 hours of symptom onset for maximum benefit, reducing illness duration by approximately 1-1.5 days 2, 3
• Can be taken with or without food, though administration with meals significantly improves gastrointestinal tolerability 2, 3

Prophylaxis Regimen:

• 75 mg once daily for 10 days following exposure 1, 2
• Should be initiated within 48 hours of exposure to infected individuals 2

Pediatric Dosing (Children ≥1 year)

Weight-based dosing is preferred for children 1-12 years: 1, 2

• ≤15 kg (≤33 lb): 30 mg twice daily for treatment; 30 mg once daily for prophylaxis 1, 2
• >15-23 kg (>33-51 lb): 45 mg twice daily for treatment; 45 mg once daily for prophylaxis 1, 2
• >23-40 kg (>51-88 lb): 60 mg twice daily for treatment; 60 mg once daily for prophylaxis 1, 2
• >40 kg (>88 lb): 75 mg twice daily for treatment; 75 mg once daily for prophylaxis 1, 2

Infant Dosing (<1 year)

Term Infants (≥2 weeks to <1 year):

• 0-8 months: 3 mg/kg per dose twice daily for treatment 1, 2
• 9-11 months: 3.5 mg/kg per dose twice daily for treatment 1, 2
• Prophylaxis (3-8 months): 3 mg/kg once daily for 10 days 1
• Prophylaxis is NOT recommended for infants <3 months unless the situation is judged critical 1

Critical Distinction for Preterm Infants

Never use term infant dosing (3 mg/kg) for preterm infants—this leads to toxic drug concentrations due to immature renal function. 2, 3 Preterm infants require substantially lower doses based on postmenstrual age (gestational age + chronological age): 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

Formulation and Administration

Available formulations: 1, 3

• Capsules: 30 mg, 45 mg, and 75 mg 1, 3
• Oral suspension: 6 mg/mL when reconstituted 1, 3

Administration with food is strongly recommended to reduce gastrointestinal side effects (nausea and vomiting), which occur in approximately 10-15% of patients. 1, 2, 3

Common Pitfalls to Avoid

• Never confuse treatment dosing (twice daily) with prophylaxis dosing (once daily)—this leads to underdosing treatment or overdosing prophylaxis 2
• Never use weight-based dosing intended for children ≥1 year (30 mg, 45 mg, 60 mg, 75 mg unit doses) in infants <1 year—these doses are too high 1
• Ensure term infant status before using 3 mg/kg dosing—if preterm, use postmenstrual age-based dosing instead 1, 2
• Do not delay treatment beyond 48 hours of symptom onset in otherwise healthy patients, as efficacy diminishes significantly 2, 3