What is the recommended dosing for Tamiflu (oseltamivir) in the treatment of influenza?

Tamiflu (Oseltamivir) Dosing Recommendations

For adults and adolescents ≥13 years, the standard treatment dose is 75 mg orally twice daily for 5 days, initiated within 48 hours of symptom onset. 1, 2

Adult and Adolescent Dosing (≥13 years)

Treatment: 75 mg orally twice daily for 5 days 1, 3, 2

• Must be initiated within 48 hours of symptom onset for maximum effectiveness 1, 3
• Earlier initiation provides greater benefit—treatment within 12 hours reduces illness duration by an additional 74.6 hours compared to treatment at 48 hours 4

Prophylaxis: 75 mg orally once daily 1, 3

• Post-exposure prophylaxis: 10 days following close contact with infected individual 1, 2
• Seasonal prophylaxis: Up to 6 weeks during community outbreak 2
• Immunocompromised patients: May continue up to 12 weeks 2

Pediatric Dosing (≥12 months)

Weight-based dosing for treatment (twice daily for 5 days): 1, 3, 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 dosing: Same weight-based doses but once daily for 10 days 1, 2

Infant Dosing (<12 months)

Term infants 0-8 months: 3 mg/kg per dose twice daily for 5 days 1, 3

Infants 9-11 months: 3.5 mg/kg per dose twice daily for 5 days 1, 3

Prophylaxis: Not recommended for infants <3 months unless situation is judged critical due to limited safety data 1

Preterm Infant Dosing

Dosing based on postmenstrual age (gestational age + chronological age): 1, 3, 2

• <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

This postmenstrual age-based dosing is essential to avoid toxicity due to immature renal function in preterm infants 1, 3

Renal Impairment Adjustments

Creatinine clearance 10-30 mL/min: 1, 3

• Treatment: 75 mg once daily for 5 days
• Prophylaxis: 30 mg once daily for 10 days OR 75 mg every other day for 10 days (5 doses total)

Dose adjustment is critical in renal insufficiency to prevent toxicity 1

Formulation and Administration

Available formulations: 1, 3, 2

• Capsules: 30 mg, 45 mg, 75 mg
• Oral suspension: 6 mg/mL when reconstituted (preferred for patients who cannot swallow capsules)

Oral suspension dosing volumes: 1, 2

• 30 mg dose = 5 mL
• 45 mg dose = 7.5 mL
• 60 mg dose = 10 mL
• 75 mg dose = 12.5 mL

Administration tips: 1, 3, 2

• Can be taken with or without food
• Taking with food improves gastrointestinal tolerability—this is important as nausea and vomiting occur in approximately 10-15% of patients 1, 4, 5
• Capsules can be opened and contents mixed with liquid if patient cannot swallow whole 1
• If commercial suspension unavailable, pharmacies can compound suspension from capsules to achieve 6 mg/mL concentration 1

Critical Clinical Pearls

Timing is everything: The 48-hour window is not arbitrary—clinical efficacy dramatically decreases with delayed initiation, with treatment within 12-24 hours providing substantially greater benefit than treatment at 48 hours 4

High-risk patients: Do not withhold treatment in patients with asthma, chronic pulmonary disease, cardiovascular disease, diabetes, or immunodeficiency—these are not contraindications 1

Pregnancy: Oseltamivir can be used during pregnancy with no contraindication 1

Live vaccine interaction: Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir use, and do not use oseltamivir for 14 days after LAIV vaccination 1

Higher doses: Standard dosing (75 mg twice daily) is appropriate for most patients; higher doses (150 mg twice daily) showed no additional benefit in hospitalized adults with influenza A, though some benefit was seen in influenza B 6