What are the recommended dosing regimens of oseltamivir (Tamiflu) for treatment and post‑exposure prophylaxis in adults, adolescents, children, infants, and patients with renal impairment?

Oseltamivir (Tamiflu) Dosing Guidelines

Treatment Dosing (5-day course)

For treatment of acute influenza, oseltamivir should be initiated within 48 hours of symptom onset and administered for 5 days regardless of symptom improvement. 1, 2

Adults and Adolescents (≥13 years)

• 75 mg orally twice daily for 5 days 1, 2, 3
• Administer with or without food, though taking with meals reduces nausea and vomiting (occurring in ~10% of patients) 1, 2

Pediatric Patients (≥12 months, weight-based)

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

Infants (term, <12 months)

• 9–11 months: 3.5 mg/kg per dose twice daily 1, 2, 4
• 0–8 months: 3 mg/kg per dose twice daily 1, 2
• FDA-approved for infants as young as 2 weeks of age 1, 3

Preterm Infants (postmenstrual age-based)

Critical: Preterm infants require substantially lower doses than term infants due to immature renal function. 1, 2

• <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
• For extremely preterm infants (<28 weeks), consult a pediatric infectious disease specialist 1, 2

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Prophylaxis Dosing (10-day course post-exposure)

Post-exposure prophylaxis should be initiated within 48 hours of close contact with a confirmed or suspected influenza case. 2

Adults and Adolescents (≥13 years)

• 75 mg orally once daily for 10 days 1, 2, 3
• During community outbreak: 75 mg once daily for up to 6 weeks 1, 3

Pediatric Patients (≥12 months, weight-based)

• ≤15 kg: 30 mg once daily 1, 2
• >15–23 kg: 45 mg once daily 1, 2
• >23–40 kg: 60 mg once daily 1, 2
• >40 kg: 75 mg once daily 1, 2
• During community outbreak: same weight-based dose once daily for up to 6 weeks 1, 3

Infants (3–11 months)

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

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Renal Impairment Dosing Adjustments

Dose adjustment is mandatory for patients with creatinine clearance <60 mL/min to prevent drug accumulation. 1, 2, 3

Creatinine Clearance 10–30 mL/min

Treatment:

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

Prophylaxis:

• 30 mg once daily for 10 days OR 75 mg every other day for 10 days (5 total doses) 1, 2, 3

End-Stage Renal Disease (ESRD)

On hemodialysis (treatment):

• 30 mg immediately, then 30 mg after every hemodialysis cycle (not to exceed 5 days) 3

On hemodialysis (prophylaxis):

• 30 mg immediately, then 30 mg after alternate hemodialysis cycles for recommended duration 3

On CAPD (treatment):

• Single 30 mg dose immediately 3

On CAPD (prophylaxis):

• 30 mg immediately, then 30 mg once weekly for recommended duration 3

Oseltamivir is NOT recommended for ESRD patients not undergoing dialysis. 3

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Formulation and Administration

Available Formulations

• Capsules: 30 mg, 45 mg, 75 mg 1, 2, 3
• Oral suspension: 6 mg/mL concentration after reconstitution 1, 2, 3

Suspension Volume Equivalents

• 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

Compounding Instructions

• If commercial suspension is unavailable, pharmacies can compound a 6 mg/mL suspension based on package insert instructions 1, 2
• Capsules can be opened and contents mixed with liquid for patients unable to swallow capsules 2

Administration Tips

• Administer with food to reduce gastrointestinal side effects (nausea, vomiting occur in 10–15% of patients) 1, 2, 5
• Use calibrated oral dosing devices (3 mL or 5 mL oral syringes) for infants—never use household spoons 2

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Critical Clinical Pitfalls to Avoid

Dosing Errors

• Never use weight-based categorical dosing (30 mg, 45 mg, etc.) for infants <12 months—these doses are too high; use mg/kg dosing instead 2, 4
• Never apply term infant dosing (3 mg/kg) to preterm infants—they require substantially lower postmenstrual age-based doses 1, 2
• Never round up to the next weight category—a child weighing 15.2 kg receives 30 mg, not 45 mg 6

Renal Function

• Do not confuse GFR with creatinine clearance when calculating renal dosing 4
• Elderly patients require renal function assessment, not just age-based dosing—dose reductions are based on creatinine clearance, not age 2

Treatment Duration

• Complete the full 5-day treatment course even if symptoms improve earlier—early discontinuation increases resistance risk 2
• The 5-day duration applies to all patients, including those with renal impairment (though dose frequency is reduced) 1, 2, 3

Drug Interactions

• Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir or for 14 days after oseltamivir use 2, 3

Measurement Accuracy

• For infants requiring mg/kg dosing, calculate the exact dose and measure the corresponding volume precisely—do not round inappropriately 2
• The syringe supplied with commercial product may be unsuitable for small infant volumes 2