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

Tamiflu (Oseltamivir) Dosage Recommendations

For adults and adolescents ≥13 years, the standard treatment dose is 75 mg orally twice daily for 5 days, and for prophylaxis, 75 mg once daily for at least 10 days (post-exposure) or up to 6 weeks (community outbreak). 1, 2

Treatment Dosing

Adults and Adolescents (≥13 years)

• 75 mg orally twice daily for 5 days 1, 3, 2
• Treatment must be initiated within 48 hours of symptom onset for maximum effectiveness 1, 3
• Can be taken with or without food, though taking with meals significantly improves gastrointestinal tolerability 1, 3

Pediatric Patients (1-12 years) - Weight-Based Dosing

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

Infants (2 weeks to <12 months)

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

Preterm Infants (Postmenstrual Age-Based)

• <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

Prophylaxis Dosing

Adults and Adolescents (≥13 years)

• 75 mg orally once daily 1, 4, 2
• Post-exposure prophylaxis: Continue for at least 10 days following close contact with infected individual 4, 2
• Community outbreak/seasonal prophylaxis: Continue up to 6 weeks 4, 2
• Immunocompromised patients: May continue up to 12 weeks 2

Pediatric Patients (1-12 years)

• Use the same weight-based doses as treatment, but once daily instead of twice daily 1, 2
• Duration: 10 days post-exposure or up to 6 weeks during community outbreak 2

Renal Impairment Adjustments

For patients with creatinine clearance 10-30 mL/min, dose reduction is mandatory to avoid toxicity: 1

Treatment Dosing

• 75 mg once daily for 5 days (instead of twice daily) 1, 3

Prophylaxis Dosing

• 30 mg once daily for 10 days OR 75 mg every other day for 10 days (5 total doses) 1

End-Stage Renal Disease

• Oseltamivir is not recommended for patients with end-stage renal disease not undergoing dialysis 2

Available Formulations

• Capsules: 30 mg, 45 mg, and 75 mg 1, 3
• Oral suspension: 6 mg/mL when reconstituted (preferred for patients who cannot swallow capsules) 1, 2
• Capsules can be opened and contents mixed with liquid if needed 1

Oral Suspension Dosing Volumes

• 30 mg dose = 5 mL 1
• 45 mg dose = 7.5 mL 1
• 60 mg dose = 10 mL 1
• 75 mg dose = 12.5 mL 1

Critical Administration Considerations

Timing is essential: Treatment efficacy is significantly enhanced when initiated within 24 hours of symptom onset, with a 37-40% reduction in illness duration compared to later initiation 5

Food administration: Taking oseltamivir with meals reduces nausea and vomiting, which occur in approximately 5-15% of patients 1, 6

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, 4

Common Pitfalls to Avoid

• Do not delay treatment waiting for laboratory confirmation in high-risk patients with suspected influenza—initiate empirically within 48 hours of symptom onset 1
• Do not use lower doses or shorter durations than recommended, as this may reduce efficacy and contribute to viral resistance 7
• Do not forget renal dose adjustments in patients with moderate to severe renal impairment, as standard dosing can lead to toxicity 1
• Do not withhold treatment due to mild illness or fever alone—these are not contraindications 1