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

Tamiflu (Oseltamivir) Dosing

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

Adult and Adolescent Dosing (≥13 years)

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

• Equivalent to 12.5 mL of oral suspension (6 mg/mL concentration) twice daily 2
• Must be initiated within 48 hours of symptom onset; earlier initiation (within 12-24 hours) provides greater benefit 1, 4

Prophylaxis: 75 mg orally once daily 1, 3

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

Pediatric Dosing (Weight-Based for Children ≥12 months)

Treatment (twice daily for 5 days): 1, 3, 2

• ≤15 kg (≤33 lb): 30 mg (5 mL) twice daily

• 15-23 kg (>33-51 lb): 45 mg (7.5 mL) twice daily

• 23-40 kg (>51-88 lb): 60 mg (10 mL) twice daily

• 40 kg (>88 lb): 75 mg (12.5 mL) twice daily

Prophylaxis (once daily for 10 days): Same weight-based doses as treatment, but administered once daily instead of twice daily 1, 2

Infant Dosing (<12 months)

Treatment (twice daily for 5 days): 1, 3

• 9-11 months: 3.5 mg/kg per dose twice daily
• Term infants 0-8 months: 3.0 mg/kg per dose twice daily

Prophylaxis (once daily for 10 days): 1

• 3-11 months: 3.0 mg/kg once daily
• <3 months: Not recommended unless situation is judged critical due to limited safety data

Preterm Infant Dosing (Based on Postmenstrual Age)

Treatment (twice daily for 5 days): 1, 3

• <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

These lower doses are essential due to immature renal function in preterm infants 1

Renal Impairment Adjustments

For creatinine clearance 10-30 mL/min: 1, 3

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

End-stage renal disease not on dialysis: Oseltamivir is not recommended 1

Formulations 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)

Administration tips: 1, 3, 4

• Can be taken with or without food
• Taking with food significantly improves gastrointestinal tolerability and reduces nausea/vomiting (occurs in ~10-15% of patients)
• Capsules can be opened and contents mixed with liquid if patient cannot swallow whole 1
• If commercial suspension unavailable, pharmacies can compound using package label instructions 1

Critical Timing Considerations

Treatment initiation: 1, 4

• Must begin within 48 hours of symptom onset for efficacy
• Treatment within 12 hours reduces illness duration by an additional 74.6 hours compared to starting at 48 hours
• Treatment within 24 hours reduces illness duration by an additional 53.9 hours compared to starting at 48 hours

Prophylaxis initiation: Should begin within 48 hours following close contact with infected individual 1

Common Pitfalls to Avoid

• Do not delay treatment waiting for laboratory confirmation in high-risk patients with suspected influenza 1
• Do not withhold oseltamivir due to mild illness or fever alone in appropriate candidates 1
• Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir use, and do not use oseltamivir for 14 days after LAIV vaccination 1
• Remember renal dose adjustments are mandatory for creatinine clearance 10-30 mL/min 1, 3