What is the recommended dosage of Tamiflu (oseltamivir)?

Oseltamivir (Tamiflu) Dosing Recommendations

Treatment Dosing

For adults and adolescents ≥13 years, administer oseltamivir 75 mg orally twice daily for 5 days, initiated within 48 hours of symptom onset for maximum effectiveness. 1, 2, 3

Adults and Adolescents (≥13 years)

• Standard dose: 75 mg orally twice daily for 5 days 1, 2, 3
• Treatment must be initiated within 48 hours of symptom onset 1, 4
• Available as capsules or oral suspension (12.5 mL of 6 mg/mL suspension = 75 mg dose) 1, 3

Pediatric Patients (≥12 months to 12 years)

Weight-based dosing is essential for children, with doses ranging from 30-75 mg twice daily depending on body weight: 1, 2, 3

• ≤15 kg (≤33 lb): 30 mg twice daily for 5 days (5 mL of oral suspension) 1, 2, 3
• >15-23 kg (>33-51 lb): 45 mg twice daily for 5 days (7.5 mL of oral suspension) 1, 2, 3
• >23-40 kg (>51-88 lb): 60 mg twice daily for 5 days (10 mL of oral suspension) 1, 2, 3
• >40 kg (>88 lb): 75 mg twice daily for 5 days (12.5 mL of oral suspension) 1, 2, 3

Infants (2 weeks to <12 months)

Age-based dosing is required for infants due to developmental differences in drug clearance: 1, 2, 4

• 9-11 months: 3.5 mg/kg per dose twice daily for 5 days 1, 2
• Term infants 0-8 months: 3 mg/kg per dose twice daily for 5 days 1, 2, 4
• Preterm infants require postmenstrual age-based dosing: 1, 2, 4
  • <38 weeks postmenstrual age: 1.0 mg/kg twice daily for 5 days 1, 2
  • 38-40 weeks postmenstrual age: 1.5 mg/kg twice daily for 5 days 1, 2

  • 40 weeks postmenstrual age: 3.0 mg/kg twice daily for 5 days 1, 2

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Prophylaxis Dosing

For post-exposure prophylaxis in adults and adolescents ≥13 years, administer 75 mg once daily for 10 days following close contact with an infected individual, or up to 6 weeks during a community outbreak. 1, 2, 3

Adults and Adolescents (≥13 years)

• 75 mg orally once daily 1, 2, 3
• Duration: 10 days for post-exposure prophylaxis 2, 3
• Duration: Up to 6 weeks for seasonal prophylaxis during community outbreak 2, 3
• Immunocompromised patients: May continue up to 12 weeks 3

Pediatric Patients (≥1 year to 12 years)

Use the same weight-based doses as treatment, but administered once daily instead of twice daily: 1, 2, 3

• ≤15 kg: 30 mg once daily for 10 days 2, 3

• 15-23 kg: 45 mg once daily for 10 days 2, 3

• 23-40 kg: 60 mg once daily for 10 days 2, 3

• 40 kg: 75 mg once daily for 10 days 2, 3

Infants (3-11 months)

• 3 mg/kg once daily for 10 days 1, 2
• Prophylaxis is not recommended for infants <3 months unless the situation is judged critical due to limited safety data 1

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Renal Impairment Adjustments

Dose reduction is mandatory for patients with moderate to severe renal impairment to prevent drug accumulation: 1, 2

Creatinine Clearance 10-30 mL/min

• Treatment: 75 mg once daily for 5 days (instead of twice daily) 1, 2, 4
• Prophylaxis: 30 mg once daily for 10 days OR 75 mg every other day for 10 days (5 total doses) 1, 2, 4

End-Stage Renal Disease

• Oseltamivir is not recommended for patients with end-stage renal disease not undergoing dialysis 3

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Formulation and Administration

Oseltamivir is available as capsules (30 mg, 45 mg, 75 mg) and oral suspension (6 mg/mL when reconstituted), with the oral suspension being the preferred formulation for patients who cannot swallow capsules. 1, 2, 3

Key Administration Points

• Can be taken with or without food, though taking with food improves gastrointestinal tolerability 1, 2, 4
• Nausea and vomiting are the most common adverse effects, occurring in approximately 1 in 7 patients 5
• Capsules can be opened and contents mixed with liquid if needed 1
• If commercial suspension unavailable, pharmacies can compound a 6 mg/mL suspension per package instructions 1

Oral Suspension Dosing Volumes (6 mg/mL concentration)

• 30 mg dose = 5 mL 1, 2, 3
• 45 mg dose = 7.5 mL 1, 2, 3
• 60 mg dose = 10 mL 1, 2, 3
• 75 mg dose = 12.5 mL 1, 2, 3

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Critical Clinical Considerations

Treatment efficacy is time-dependent and significantly diminished if not initiated within 48 hours of symptom onset. 1, 4

Drug Interactions

• Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir administration 1, 2
• Do not use oseltamivir for 14 days after LAIV vaccination 1, 2

Common Pitfalls to Avoid

• Do not use adult dosing in children—weight-based dosing is essential to achieve therapeutic drug levels 6
• Do not forget renal dose adjustments—failure to adjust can lead to drug accumulation and toxicity 1
• Do not use for prophylaxis in infants <3 months except in critical situations 1
• Do not rely on oseltamivir as a substitute for annual influenza vaccination 3