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

Tamiflu (Oseltamivir) Dosing for Influenza Treatment and Prevention

For adults and adolescents ≥13 years, administer oseltamivir 75 mg orally twice daily for 5 days for treatment and 75 mg once daily for 10 days for prophylaxis. 1

Treatment Dosing

Adults and Adolescents (≥13 years)

• 75 mg orally twice daily for 5 days 2, 1
• Initiate treatment within 48 hours of symptom onset for optimal benefit 2, 1
• Treatment after 48 hours may still provide benefit in moderate-to-severe or progressive disease 2

Pediatric Patients (≥12 months) - Weight-Based Dosing

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

Infants (9-11 months)

• 3.5 mg/kg per dose twice daily for 5 days 2

Term Infants (0-8 months)

• 3 mg/kg per dose twice daily for 5 days 2
• FDA approved down to 2 weeks of age 2, 1

Preterm Infants - Postmenstrual Age-Based Dosing

• <38 weeks postmenstrual age: 1.0 mg/kg twice daily 2
• 38-40 weeks postmenstrual age: 1.5 mg/kg twice daily 2
• >40 weeks postmenstrual age: 3.0 mg/kg twice daily 2
• Lower dosing required due to immature renal function 2

Prophylaxis Dosing

Adults and Adolescents (≥13 years)

• 75 mg orally once daily for 10 days (post-exposure prophylaxis) 2, 1
• May continue up to 6 weeks during community outbreak 1
• Immunocompromised patients may continue up to 12 weeks 1

Pediatric Patients (≥12 months) - Weight-Based Dosing

• Same weight-based doses as treatment, but once daily for 10 days 2, 1
• ≤15 kg: 30 mg once daily 2

• 15-23 kg: 45 mg once daily 2

• 23-40 kg: 60 mg once daily 2

• 40 kg: 75 mg once daily 2

Infants (3-11 months)

• 3 mg/kg once daily for 10 days 2
• Not recommended for infants <3 months unless situation judged critical due to limited safety data 2

Renal Impairment Adjustments

Creatinine Clearance 10-30 mL/min

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

Formulation and Administration

Available Formulations

• Capsules: 30 mg, 45 mg, 75 mg 2, 1
• Oral suspension: 6 mg/mL when reconstituted 2, 1

Suspension Dosing Volumes (6 mg/mL concentration)

• 30 mg dose = 5 mL 2, 1
• 45 mg dose = 7.5 mL 2, 1
• 60 mg dose = 10 mL 2, 1
• 75 mg dose = 12.5 mL 2, 1

Administration Tips

• May be taken with or without food, though administration with meals improves gastrointestinal tolerability 2, 1
• If commercial suspension unavailable, capsules may be opened and mixed with simple syrup or Ora-Sweet SF to achieve 6 mg/mL concentration 2

Important Clinical Considerations

Timing of Therapy

• Initiate treatment within 48 hours of symptom onset for maximum benefit 2, 1
• Earlier treatment (within 24 hours) provides faster symptom resolution 3
• Treatment beyond 48 hours may still benefit patients with moderate-to-severe or progressive disease 2

Common Adverse Effects

• Nausea and vomiting are most common (5-15% of patients) 4
• Gastrointestinal effects are mild, transient, and less likely when taken with food 2, 5

Drug Interactions

• Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir 6
• Do not use oseltamivir for 14 days after LAIV vaccination 6

Clinical Efficacy

• Reduces duration of illness by 19-30% (approximately 1-1.5 days) when initiated within 36 hours of symptom onset 5, 7, 3
• Decreases incidence of secondary complications and antibiotic use 5, 8, 7
• Effective in high-risk populations including elderly and those with chronic cardiac or respiratory disease 8, 7