What is the recommended dose of Tamiflu (oseltamivir) for a patient with influenza, considering age and renal function?

Tamiflu (Oseltamivir) Dosing Recommendations

For adults and adolescents ≥13 years, the standard treatment dose is 75 mg orally twice daily for 5 days, with prophylaxis at 75 mg once daily for 10 days; dose adjustments are mandatory when creatinine clearance falls below 60 mL/min. 1

Adult and Adolescent Dosing (≥13 years)

Treatment Dosing

• The FDA-approved treatment regimen is 75 mg orally twice daily for 5 days, initiated within 48 hours of symptom onset. 1
• Treatment should be started as early as possible—initiation within 12 hours of symptom onset reduces illness duration by 3.1 days (41%) compared to starting at 48 hours. 2
• Administration with meals significantly reduces gastrointestinal side effects (nausea/vomiting), which occur in approximately 10-15% of patients. 3, 4, 5

Prophylaxis Dosing

• The FDA-approved prophylaxis dose is 75 mg orally once daily for at least 10 days following close contact with an infected individual, and up to 6 weeks during a community outbreak. 1
• In immunocompromised patients, prophylaxis may be continued for up to 12 weeks. 1
• Prophylaxis should be initiated within 48 hours of exposure to infected individuals. 3, 5

Pediatric Dosing (1-12 years)

Weight-based dosing is mandatory for children, with specific doses determined by body weight. 1

Treatment Dosing (5 days)

• ≤15 kg: 30 mg twice daily (5 mL of 6 mg/mL suspension) 1
• >15-23 kg: 45 mg twice daily (7.5 mL of suspension) 1
• >23-40 kg: 60 mg twice daily (10 mL of suspension) 1
• >40 kg: 75 mg twice daily (12.5 mL of suspension) 1

Prophylaxis Dosing (10 days)

• Same weight-based doses as treatment, but given once daily instead of twice daily. 1

Infant Dosing (<1 year)

For term infants 2 weeks to <1 year, the FDA-approved treatment dose is 3 mg/kg per dose twice daily for 5 days. 1

• The American Academy of Pediatrics recommends 3 mg/kg twice daily for infants 0-8 months and 3.5 mg/kg twice daily for 9-11 months. 6
• Prophylaxis is not FDA-approved for infants <1 year. 1
• The American Academy of Pediatrics does not recommend prophylaxis for infants <3 months due to limited safety data unless the situation is judged critical. 6, 4

Critical Caveat for Preterm Infants

Never use term infant dosing (3 mg/kg) for preterm infants—this leads to toxic drug concentrations due to immature renal function. 6, 3, 4, 5

• Preterm infants require lower doses based on postmenstrual age (PMA), as they have reduced clearance of oseltamivir. 6

Renal Impairment Dosing Adjustments

Dose adjustments are mandatory for patients with creatinine clearance <60 mL/min. 3, 4, 5

Treatment Dosing Adjustments

• CrCl 30-60 mL/min: 75 mg once daily for 5 days (instead of twice daily) 3, 4, 5
• CrCl 10-30 mL/min: 75 mg once daily for 5 days or 30 mg once daily for 5 days 3, 4, 5
• End-stage renal disease not on dialysis: Oseltamivir is not recommended. 1

Prophylaxis Dosing Adjustments

• CrCl 10-30 mL/min: 30 mg once daily or 75 mg every other day for 10 days (5 total doses) 3

Pediatric Renal Dosing

• Renal dosing for pediatric patients is not available in the FDA package insert. 6
• The CDC provides dosing tables for children who qualify for adult doses based on weight >40 kg. 6

Special Populations

Pregnancy and Breastfeeding

• Pregnant women receive the same dosing as non-pregnant adults: 75 mg twice daily for 5 days. 4, 5
• Breastfeeding is not a contraindication to oseltamivir use. 4, 5

Elderly Patients (≥65 years)

• Elderly patients with normal renal function should receive standard adult dosing (75 mg twice daily). 3
• Dose reductions are mandatory when creatinine clearance falls below 60 mL/min, regardless of age. 3

Formulation Details

• Oseltamivir is available as 30 mg, 45 mg, and 75 mg capsules. 6, 4
• Oral suspension is available at 6 mg/mL concentration when reconstituted from powder. 6, 4, 1
• The oral suspension is the preferred formulation for patients who cannot swallow capsules, particularly infants and young children. 4, 1
• For infants <1 year, use an appropriate measuring device (3 mL or 5 mL oral syringe) instead of the standard syringe supplied. 6

Critical Timing Considerations

Treatment should be initiated within 48 hours of symptom onset for maximum benefit, though should not be withheld in high-risk or hospitalized patients presenting beyond 48 hours. 5, 1

• Earlier initiation provides progressively greater benefit—starting within 12 hours reduces illness duration by 3.1 days compared to starting at 48 hours. 2
• Treatment reduces illness duration by 1-1.5 days when started within 48 hours. 3, 5
• Prophylaxis should be started within 48 hours of exposure to infected individuals. 3, 5

Common Pitfalls to Avoid

Do not confuse treatment dosing (twice daily) with prophylaxis dosing (once daily)—this leads to underdosing treatment or overdosing prophylaxis. 3, 4, 5

Never use term infant dosing for preterm infants due to risk of toxic drug concentrations from immature renal function. 6, 3, 4, 5

Always take oseltamivir with food to significantly reduce gastrointestinal side effects (nausea/vomiting). 3, 4, 5

Do not forget to adjust doses for renal impairment when creatinine clearance is <60 mL/min. 3, 4, 5