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

Tamiflu (Oseltamivir) Dosage

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. 1, 2, 3

Treatment Dosing (5 Days Duration)

Adults and Adolescents (≥13 years)

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

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

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

Infants (<12 months)

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

Preterm Infants (Postmenstrual Age-Based)

• <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

Prophylaxis Dosing

Adults and Adolescents (≥13 years)

• 75 mg orally once daily 1, 3
• Duration: 10 days for post-exposure prophylaxis 1, 3
• Duration: Up to 6 weeks for seasonal/community outbreak prophylaxis 1, 3
• Duration: Up to 12 weeks in immunocompromised patients 1, 3
• Must be initiated within 48 hours following close contact with an infected individual 1

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

• ≤15 kg: 30 mg once daily 1, 3
• >15-23 kg: 45 mg once daily 1, 3
• >23-40 kg: 60 mg once daily 1, 3
• >40 kg: 75 mg once daily 1, 3
• Duration: 10 days post-exposure or up to 6 weeks for community outbreak 1, 3

Infants (3-11 months)

• 3 mg/kg once daily for 10 days 1
• Prophylaxis is not recommended for infants <3 months unless the situation is judged critical due to limited safety data 1

Renal Impairment Adjustments

For patients with creatinine clearance 10-30 mL/min, dose reduction is essential to avoid toxicity: 1, 2, 3

Treatment Dosing

• 75 mg once daily (instead of twice daily) for 5 days 1, 2, 3

Prophylaxis Dosing

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

Formulations and Administration

Available Forms

• Capsules: 30 mg, 45 mg, and 75 mg 1, 2, 3
• Oral suspension: 6 mg/mL when reconstituted 1, 2, 3

Oral Suspension Dosing Volumes

• 30 mg dose = 5 mL 1, 3
• 45 mg dose = 7.5 mL 1, 3
• 60 mg dose = 10 mL 1, 3
• 75 mg dose = 12.5 mL 1, 3

Administration Tips

• Capsules can be opened and contents mixed with liquid for patients who cannot swallow capsules whole 1
• If commercial oral suspension is unavailable, pharmacies can compound a suspension using capsule contents mixed with simple syrup or Ora-Sweet SF to achieve 6 mg/mL concentration 1
• For infants <1 year, use an appropriate dosing device that can accurately measure small volumes 3

Critical Clinical Considerations

Timing

Treatment must be initiated within 48 hours of symptom onset for maximum benefit - this reduces illness duration by 29-35 hours (25-30% reduction) compared to placebo 1, 4. Earlier initiation within 24 hours provides even greater benefit, reducing symptoms by 37-40% 4.

Common Adverse Effects

• Nausea and vomiting occur in approximately 5-15% of patients (compared to 8% on placebo) 1
• Gastrointestinal effects are mild, transient, and significantly reduced when taken with food 1, 5
• Headache and skin reactions may also occur 1

Drug Interactions

Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir use, and do not use oseltamivir for 14 days after LAIV vaccination 1

Special Populations

• Oseltamivir is approved for use in children as young as 2 weeks of age with appropriate dosing 1, 2
• Can be used during pregnancy with no contraindications 1
• Patients with asthma, chronic pulmonary disease, cardiovascular disease, diabetes, and immunodeficiency can receive oseltamivir 1