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

Tamiflu (Oseltamivir) Dosage and Usage Guidelines

Tamiflu (oseltamivir) should be administered at 75 mg twice daily for 5 days in adults and adolescents ≥13 years for treatment of influenza, with weight-based dosing for children, and treatment should be initiated within 48 hours of symptom onset for maximum efficacy. 1, 2, 3

Treatment Dosage Recommendations

Adults and Adolescents (≥13 years)

• 75 mg twice daily for 5 days 4, 1, 3

Children (≥12 months) - Weight-based dosing

• ≤15 kg (≤33 lb): 30 mg twice daily for 5 days 4, 1, 2

• 15-23 kg (33-51 lb): 45 mg twice daily for 5 days 4, 1, 2

• 23-40 kg (51-88 lb): 60 mg twice daily for 5 days 4, 1, 2

• 40 kg (>88 lb): 75 mg twice daily for 5 days 4, 1, 2

Infants (<12 months)

• 9-11 months: 3.5 mg/kg per dose twice daily for 5 days 4, 1, 2
• 0-8 months (term): 3 mg/kg per dose twice daily for 5 days 4, 1, 2

Preterm Infants

• Dosing based on postmenstrual age (gestational age + chronological age) 4, 1:
  • <38 weeks postmenstrual age: 1.0 mg/kg twice daily 1
  • 38-40 weeks postmenstrual age: 1.5 mg/kg twice daily 1

  • 40 weeks postmenstrual age: 3.0 mg/kg twice daily 1

• For extremely preterm infants (<28 weeks), consultation with a pediatric infectious disease physician is recommended 4

Prophylaxis Dosage Recommendations

Adults and Adolescents (≥13 years)

• 75 mg once daily for 10 days following exposure or up to 6 weeks during community outbreaks 4, 3

Children (1-12 years) - Weight-based dosing

• ≤15 kg (≤33 lb): 30 mg once daily for 10 days 4, 3

• 15-23 kg (33-51 lb): 45 mg once daily for 10 days 4, 3

• 23-40 kg (51-88 lb): 60 mg once daily for 10 days 4, 3

• 40 kg (>88 lb): 75 mg once daily for 10 days 4, 3

Special Populations

Renal Impairment

• For patients with creatinine clearance 10-30 mL/min 4, 1:
  • Treatment: 75 mg once daily for 5 days 4, 1
  • Prophylaxis: 30 mg once daily for 10 days or 75 mg every other day for 10 days (5 doses) 4, 1

Immunocompromised Patients

• Prophylaxis may be continued for up to 12 weeks 3

Formulation and Administration

• Available as capsules (30 mg, 45 mg, and 75 mg) and oral suspension (6 mg/mL when reconstituted) 4, 1, 3
• Oral suspension dosing 4, 1:
  • 30 mg dose = 5 mL
  • 45 mg dose = 7.5 mL
  • 60 mg dose = 10 mL
  • 75 mg dose = 12.5 mL
• Can be taken with or without food, though administration with food may improve gastrointestinal tolerability 4, 1, 3, 5

Clinical Pearls

• Treatment should be initiated within 48 hours of symptom onset for maximum efficacy 1, 6, 7
• Earlier treatment provides greater benefits: initiation within 12 hours after symptom onset reduces illness duration by 74.6 hours (3.1 days) compared to starting at 48 hours 6, 7
• Treatment reduces the incidence of secondary complications such as otitis media, bronchitis, pneumonia, and sinusitis 6, 5, 8
• In high-risk patients with chronic respiratory or cardiac diseases, oseltamivir reduces symptom duration by 36.8% and severity by 43.1% 8
• Extended treatment beyond 5 days generally shows no additional benefit except possibly in critically ill patients 9

Common Adverse Events

• Gastrointestinal effects (nausea, vomiting) occur in approximately 10% of patients 1, 6, 5
• These side effects are typically mild, transient (resolving within 1-2 days), and can be minimized by taking with food 1, 6, 5, 7

Resistance Considerations

• Resistance to oseltamivir has been rarely observed and appears to have limited clinical relevance due to reduced transmissibility and pathogenicity of resistant strains 6
• Oseltamivir remains effective against most circulating influenza strains, including influenza A (H1N1) and A (H3N2) 2