What are the dosing orders for Tamiflu (oseltamivir)?

Tamiflu (Oseltamivir) Dosing Orders

For adults and adolescents ≥13 years, prescribe oseltamivir 75 mg orally twice daily for 5 days for treatment, or 75 mg once daily for prophylaxis, with treatment initiated within 48 hours of symptom onset for maximum effectiveness. 1, 2

Treatment Dosing (5 Days)

Adults and Adolescents (≥13 years)

• 75 mg orally twice daily for 5 days 1, 2
• Equivalent to 12.5 mL of oral suspension (6 mg/mL) twice daily 1
• Must initiate within 48 hours of symptom onset 1, 3

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

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

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
• Preterm infants (postmenstrual age-based):
  • <38 weeks: 1.0 mg/kg twice daily 1
  • 38-40 weeks: 1.5 mg/kg twice daily 1

  • 40 weeks: 3.0 mg/kg twice daily 1

Prophylaxis Dosing (10 Days Post-Exposure)

Adults and Adolescents (≥13 years)

• 75 mg orally once daily for 10 days after exposure 1, 2
• For community outbreaks: continue up to 6 weeks 4, 2
• For immunocompromised patients: may extend up to 12 weeks 2
• Initiate within 48 hours of close contact with infected individual 1

Pediatric Patients (≥1 year to 12 years) - 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

Infants (3-11 months)

• 3 mg/kg once daily for 10 days 1, 2
• Prophylaxis NOT recommended for infants <3 months unless situation is critical 1

Renal Impairment Adjustments

Dose adjustments are mandatory when creatinine clearance falls below 60 mL/min. 1

Treatment Dosing

• CrCl >60-90 mL/min: 75 mg twice daily (no adjustment) 2
• CrCl >30-60 mL/min: 30 mg twice daily for 5 days 2
• CrCl 10-30 mL/min: 30 mg once daily for 5 days OR 75 mg once daily 1, 2
• Hemodialysis: 30 mg immediately, then 30 mg after each hemodialysis cycle (max 5 days) 2
• CAPD: Single 30 mg dose 2
• ESRD not on dialysis: NOT recommended 2

Prophylaxis Dosing

• CrCl 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
• Hemodialysis: 30 mg immediately, then 30 mg after alternate hemodialysis cycles 2

Formulations and Administration

Available Forms

• Capsules: 30 mg, 45 mg, 75 mg 1, 3
• Oral suspension: 6 mg/mL when reconstituted 1, 2
• Capsules can be opened and mixed with liquid if patient cannot swallow whole 1

Administration Pearls

• Take with food to improve gastrointestinal tolerability 1, 3, 5
• Nausea and vomiting occur in 5-15% of patients but are mild and transient 1, 5
• Oral suspension stable for 17 days refrigerated or 10 days at room temperature after reconstitution 2
• Use appropriate oral dosing dispenser that measures volume in mL 2

Critical Timing Considerations

Treatment efficacy is highly time-dependent—earlier initiation produces better outcomes. 5

• Treatment within 12 hours of symptom onset reduces illness duration by an additional 74.6 hours compared to treatment at 48 hours 5
• Treatment within 24 hours reduces illness duration by an additional 53.9 hours compared to treatment at 48 hours 5
• Maximum benefit requires initiation within 48 hours of symptom onset 1, 3, 5
• For prophylaxis, initiate within 48 hours of close contact with infected individual 1

Special Populations

Older Adults (≥65 years)

• Standard dosing (75 mg twice daily) for those with normal renal function 1
• Age itself does not require dose adjustment—only renal function matters 1
• Always assess creatinine clearance, as dose reductions are mandatory when CrCl <60 mL/min 1

Pregnancy

• No contraindication to oseltamivir use during pregnancy 1

Healthcare Workers During Outbreaks

• 75 mg once daily for minimum 2 weeks, up to 6 weeks during community outbreak 4
• Continue until approximately 1 week after outbreak ends 4

Drug Interactions

• Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir use 1
• Do not use oseltamivir for 14 days after LAIV vaccination 1
• Low potential for drug interactions overall 6

Common Pitfalls to Avoid

• Do not delay treatment waiting for laboratory confirmation in high-risk patients—initiate empirically 1
• Do not withhold oseltamivir due to mild illness or fever alone 1
• Do not forget renal dose adjustments—serum concentrations increase proportionally with declining renal function 1
• Do not use standard dosing in preterm infants—they require substantially lower doses due to immature renal function 1
• For infants <1 year, provide dosing device that can accurately measure small volumes 2