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

Oseltamivir (Tamiflu) Dosing Recommendations

For adults and adolescents ≥13 years, administer oseltamivir 75 mg orally twice daily for 5 days for treatment of influenza, initiated within 48 hours of symptom onset. 1, 2, 3

Adult and Adolescent Dosing (≥13 years)

• Standard treatment dose: 75 mg orally twice daily for 5 days 1, 2, 3
• Treatment should be initiated within 48 hours of symptom onset for maximum effectiveness, with earlier initiation (within 12-24 hours) providing even greater benefit 1, 4
• Can be taken with or without food, though administration with food improves gastrointestinal tolerability 1, 2, 3

Pediatric Dosing (≥12 months)

Weight-based dosing is recommended for children ≥12 months: 1, 2, 3

• ≤15 kg (≤33 lb): 30 mg twice daily for 5 days 1, 2, 3
• >15-23 kg (33-51 lb): 45 mg twice daily for 5 days 1, 2, 3
• >23-40 kg (51-88 lb): 60 mg twice daily for 5 days 1, 2, 3
• >40 kg (>88 lb): 75 mg twice daily for 5 days 1, 2, 3

Infant Dosing (<12 months)

Age-based dosing for term infants: 1, 2

• 9-11 months: 3.5 mg/kg per dose twice daily for 5 days 1, 2
• 0-8 months: 3 mg/kg per dose twice daily for 5 days 1, 2

Preterm Infant Dosing

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

• <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
• Preterm infants require lower weight-based dosing due to immature renal function 1

Renal Impairment Adjustments

For patients with creatinine clearance 10-30 mL/min: 1, 2

• Treatment: 75 mg once daily for 5 days 1, 2
• Prophylaxis: 30 mg once daily for 10 days OR 75 mg every other day for 10 days (5 doses total) 1

Prophylaxis Dosing

Post-exposure prophylaxis (initiate within 48 hours of contact): 3

• Adults/adolescents ≥13 years: 75 mg once daily for at least 10 days 3
• Seasonal prophylaxis: 75 mg once daily for up to 6 weeks during community outbreak 3
• Immunocompromised patients: May continue for up to 12 weeks 3

Formulation Options

Available formulations: 1, 2, 3

• Capsules: 30 mg, 45 mg, 75 mg 1, 2, 3
• Oral suspension: 6 mg/mL when reconstituted (preferred for patients who cannot swallow capsules) 1, 3
• Oral suspension volumes: 30 mg = 5 mL, 45 mg = 7.5 mL, 60 mg = 10 mL, 75 mg = 12.5 mL 1

Critical Timing Considerations

The efficacy of oseltamivir is highly time-dependent: 1, 4

• Treatment within 12 hours of symptom onset reduces illness duration by an additional 74.6 hours compared to treatment at 48 hours 4
• Treatment within 24 hours reduces illness duration by an additional 53.9 hours compared to treatment at 48 hours 4
• Maximum benefit occurs when initiated within 48 hours of symptom onset 1, 2, 3

Common Pitfalls and Caveats

• Gastrointestinal effects (nausea, vomiting, diarrhea) occur in approximately 10% of patients but are typically mild and transient, resolving within 1-2 days 4
• Taking oseltamivir with meals significantly improves gastrointestinal tolerability 1, 2, 3
• Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir use, and do not use oseltamivir for 14 days after LAIV vaccination 1
• Weight-based dosing is preferred over age-based dosing in children when weight is known 2