What is the recommended dosing for Tamiflu (Oseltamivir) in the treatment of influenza?

Tamiflu (Oseltamivir) Dosing Recommendations

For adults and adolescents ≥13 years, the standard treatment dose is 75 mg orally twice daily for 5 days, and treatment must be initiated within 48 hours of symptom onset for maximum effectiveness. 1, 2, 3

Adult and Adolescent Dosing (≥13 years)

Treatment of Influenza

• 75 mg orally twice daily for 5 days 1, 2, 3
• Initiate therapy within 48 hours of symptom onset 2, 4
• Earlier initiation provides greater benefit—starting within 12 hours of fever onset reduces illness duration by 3.1 days more than starting at 48 hours 4

Prophylaxis of Influenza

• 75 mg orally once daily 3
• Duration: At least 10 days following close contact with infected individual 3
• Up to 6 weeks during community outbreak 3
• Up to 12 weeks in immunocompromised patients 3

Pediatric Dosing (Weight-Based for Children ≥12 months)

Treatment Dosing (Twice Daily for 5 Days)

• ≤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

Prophylaxis Dosing (Once Daily for 10 Days)

• Same weight-based doses as treatment, but given once daily instead of twice daily 3

Infant Dosing (<12 months)

Term Infants

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

Preterm Infants (Based on Postmenstrual Age)

• <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

Renal Impairment Dosing Adjustments

Treatment in Renal Impairment

• Creatinine clearance 10-30 mL/min: 75 mg once daily for 5 days (instead of twice daily) 1, 2, 3

Prophylaxis in Renal Impairment

• Creatinine clearance 10-30 mL/min: 30 mg once daily for 10 days OR 75 mg every other day for 10 days (5 total doses) 1, 2

End-Stage Renal Disease

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

Formulations and Administration

Available Formulations

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

Oral Suspension Volume Conversions

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

Administration Tips

• Can be taken with or without food, but taking with food improves gastrointestinal tolerability 1, 2, 3
• This is particularly important as nausea and vomiting are the most common adverse events 1, 5

Critical Clinical Pearls

Timing of Initiation

• Maximum benefit occurs when treatment starts within 48 hours of symptom onset 2, 6
• Earlier is better—each 12-hour delay reduces therapeutic benefit proportionally 4

Common Adverse Events

• Gastrointestinal effects (nausea, vomiting, diarrhea) are most common 1, 5
• These are typically mild, transient, and occur mainly with first dosing 5, 4
• Taking with food significantly reduces GI side effects 1, 2

Drug Interaction Warning

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

Limitations

• Oseltamivir is not a substitute for annual influenza vaccination 3
• Effectiveness may be reduced by viral resistance or changes in viral virulence 3