What is the recommended dosing for Tamiflu (oseltamivir) in patients with influenza?

Tamiflu (Oseltamivir) Dosing

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

Treatment Dosing by Age Group

Adults and Adolescents (≥13 years)

• 75 mg orally twice daily for 5 days 1, 2
• Initiate treatment within 48 hours of symptom onset 1
• Can be taken with or without food, though taking with meals reduces gastrointestinal side effects 1, 2

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

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

Infants (0-11 months)

• 9-11 months: 3.5 mg/kg per dose twice daily for 5 days 1
• Term infants 0-8 months: 3 mg/kg per dose twice daily for 5 days 1, 2

Preterm Infants (Postmenstrual Age-Based)

• <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

Prophylaxis Dosing

Adults and Adolescents (≥13 years)

• 75 mg orally once daily 1, 3, 2
• Post-exposure prophylaxis: Continue for at least 10 days following close contact with infected individual 1, 2
• Seasonal/community outbreak prophylaxis: Continue up to 6 weeks 1, 3, 2
• Immunocompromised patients: May continue up to 12 weeks 2

Pediatric Patients (1-12 years)

• Use the same weight-based doses as treatment, but once daily instead of twice daily 1, 2
• Duration: 10 days post-exposure or up to 6 weeks during community outbreak 2

Infants (3-11 months)

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

Renal Impairment Adjustments

For creatinine clearance 10-30 mL/min: 1

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

Not recommended for end-stage renal disease patients not undergoing dialysis 2

Formulations and Administration

Available Forms

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

Oral Suspension Dosing Volumes

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

Administration Tips

• Capsules can be opened and mixed with liquid if patient cannot swallow whole 1
• Taking with food significantly improves gastrointestinal tolerability and reduces nausea/vomiting, which occur in 5-15% of patients 1, 3
• If commercial suspension unavailable, pharmacies can compound using capsule contents mixed with simple syrup or Ora-Sweet SF to achieve 6 mg/mL concentration 1

Critical Clinical Pearls

Timing Considerations

• Treatment must be initiated within 48 hours of symptom onset for maximum effectiveness 1
• For high-risk patients, initiate empiric treatment without waiting for laboratory confirmation 1

Drug Interactions

• Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir use 1, 3
• Do not use oseltamivir for 14 days after LAIV vaccination 1, 3

Common Pitfalls

• Gastrointestinal effects (nausea, vomiting, diarrhea) are the most common adverse events 1
• These effects are mild, transient, and significantly reduced when taken with food 1, 4
• Preterm infants require postmenstrual age-based dosing due to immature renal function—using standard pediatric dosing risks toxicity 1

Special Populations

• Safe in pregnancy with no contraindications 1
• Can be used in patients with asthma, chronic pulmonary disease, cardiovascular disease, diabetes, and immunodeficiency 1
• Approved for use in children as young as 2 weeks of age with appropriate dosing adjustments 1, 2