What is the recommended dose and frequency of Tamiflu (oseltamivir) for influenza treatment?

Tamiflu (Oseltamivir) Dosing and Frequency

For adults and adolescents ≥13 years, the standard treatment dose is 75 mg orally twice daily for 5 days, and for prophylaxis, 75 mg once daily for 10 days post-exposure or up to 6 weeks during community outbreaks. 1, 2, 3

Adult and Adolescent Dosing (≥13 years)

Treatment Dosing

• 75 mg orally twice daily for 5 days 1, 2, 3
• Initiate treatment within 48 hours of symptom onset for maximum effectiveness 1, 2
• Treatment should not be delayed while waiting for laboratory confirmation in high-risk patients 2

Prophylaxis Dosing

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

Pediatric Dosing (≥12 months to 12 years)

Treatment Dosing (Twice Daily for 5 Days)

Weight-based dosing is essential for children: 1, 2, 3

• ≤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 administered once daily instead of twice daily: 1, 2, 3

• ≤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

Infant Dosing (<12 months)

Treatment Dosing (Twice Daily for 5 Days)

• 9-11 months: 3.5 mg/kg per dose twice daily 1, 2
• Term infants 0-8 months: 3.0 mg/kg per dose twice daily 1, 2
• Infants ≥2 weeks: Approved for treatment 1, 3

Prophylaxis Dosing

• 3-11 months: 3.0 mg/kg once daily for 10 days 1, 2
• <3 months: Not recommended unless situation is judged critical due to limited safety data 1

Preterm Infant Dosing

Dosing based on postmenstrual age (gestational age + chronological age) 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

Renal Impairment Adjustments

For Creatinine Clearance 10-30 mL/min:

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

Formulation and Administration

Available Formulations

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

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

• Can be taken with or without food, though taking with food may improve gastrointestinal tolerability 1, 3
• Capsules can be opened and contents mixed with liquid if patient cannot swallow capsules 1
• If commercial suspension unavailable, pharmacies can compound using capsule contents to achieve 6 mg/mL concentration 1

Critical Timing Considerations

• Treatment should be initiated within 48 hours of symptom onset for maximum benefit 1, 2, 3
• Earlier initiation (within 24 hours) provides even greater benefit, reducing illness duration by up to 40% 4
• Do not withhold treatment in high-risk or hospitalized patients even when presenting beyond 48 hours, as mortality benefit persists 2
• Prophylaxis should be initiated within 48 hours following close contact with infected individual 1, 3

Special Populations

Pregnancy

• Pregnant women receive the same dosing as non-pregnant persons: 75 mg twice daily for 5 days 2
• Oseltamivir is preferred over zanamivir in pregnancy 2
• Safe throughout all trimesters and postpartum period 2

Immunocompromised Patients

• Should receive treatment regardless of time since symptom onset 2
• May require extended treatment duration beyond 5 days if illness is prolonged 2
• Prophylaxis may be continued for up to 12 weeks 3

Common Pitfalls to Avoid

• Do not delay treatment waiting for laboratory confirmation in high-risk patients, as rapid antigen tests have poor sensitivity 2
• Do not withhold treatment due to presentation beyond 48 hours in hospitalized or high-risk patients, as mortality benefit persists 2
• Do not use live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir, and avoid oseltamivir for 14 days after LAIV vaccination 1, 2
• Do not underdose preterm infants - use postmenstrual age-based dosing to avoid toxicity from immature renal function 1

Adverse Effects

• Nausea and vomiting are most common (5-15% of patients), typically mild and transient 1
• Gastrointestinal effects occur in approximately 1 in 7 oseltamivir-treated patients versus 1 in 12 placebo recipients 5
• Taking with food significantly reduces gastrointestinal adverse effects 1, 3