What is the recommended dosing for oseltamivir (Tamiflu) in adults and children for the treatment and prophylaxis of influenza?

Oseltamivir Dosing Chart

For treatment of influenza, adults and adolescents ≥13 years should receive oseltamivir 75 mg orally twice daily for 5 days, while pediatric patients require weight-based dosing ranging from 30-75 mg twice daily, and infants need age-specific or postmenstrual age-based dosing starting at 3 mg/kg twice daily. 1, 2, 3

Treatment Dosing

Adults and Adolescents (≥13 years)

• 75 mg orally twice daily for 5 days 1, 2, 3
• Initiate within 48 hours of symptom onset for maximum effectiveness 1, 4
• Can be taken with or without food, though taking with meals reduces gastrointestinal side effects 1, 3

Pediatric Patients (1-12 years) - Weight-Based Dosing

• ≤15 kg (≤33 lb): 30 mg twice daily for 5 days 1, 2, 3
• >15-23 kg (>33-51 lb): 45 mg twice daily for 5 days 1, 2, 3
• >23-40 kg (>51-88 lb): 60 mg twice daily for 5 days 1, 2, 3
• >40 kg (>88 lb): 75 mg twice daily for 5 days 1, 2, 3

Infants (2 weeks to <12 months)

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

Preterm Infants - Postmenstrual Age-Based Dosing

• <38 weeks postmenstrual age: 1.0 mg/kg twice daily for 5 days 1, 2
• 38-40 weeks postmenstrual age: 1.5 mg/kg twice daily for 5 days 1, 2
• >40 weeks postmenstrual age: 3.0 mg/kg twice daily for 5 days 1, 2

Prophylaxis Dosing

Adults and Adolescents (≥13 years)

• 75 mg orally once daily for at least 10 days (post-exposure prophylaxis) 2, 5, 3
• Can be continued up to 6 weeks during community outbreak 2, 3
• In immunocompromised patients, may continue up to 12 weeks 3

Pediatric Patients (1-12 years)

• Use same weight-based doses as treatment, but once daily instead of twice daily for 10 days 2, 3
• ≤15 kg: 30 mg once daily 2

• 15-23 kg: 45 mg once daily 2

• 23-40 kg: 60 mg once daily 2

• 40 kg: 75 mg once daily 2

Infants (3-11 months)

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

Renal Impairment Adjustments

Treatment Dosing

• Creatinine clearance 10-30 mL/min: 75 mg once daily for 5 days 1, 2

Prophylaxis Dosing

• 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, 5

End-Stage Renal Disease

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

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

Oral 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

• Capsules can be opened and contents mixed with liquid if patient cannot swallow whole 1
• If commercial suspension unavailable, pharmacies can compound using capsule contents mixed with simple syrup or Ora-Sweet SF to achieve 6 mg/mL concentration 1
• Taking with food improves gastrointestinal tolerability, as nausea and vomiting occur in approximately 5-15% of patients 1, 4, 6

Special Populations

Pregnancy

• Pregnant women receive the same dosing as nonpregnant persons: 75 mg twice daily for 5 days 2
• No contraindication exists for use during pregnancy, and oseltamivir is preferred over zanamivir 1, 2

Breastfeeding

• Breastfeeding mothers requiring antivirals should receive oseltamivir, and it is not a reason to discontinue breastfeeding 2

Critical Timing Considerations

Treatment must be initiated within 48 hours of symptom onset for clinical benefit. 1, 3, 4 Earlier initiation provides greater benefit: treatment within 12 hours reduces illness duration by an additional 74.6 hours compared to treatment at 48 hours, while treatment within 24 hours provides an additional 53.9 hours of benefit. 4

Common Pitfalls to Avoid

• Do not confuse prophylaxis dosing (once daily) with treatment dosing (twice daily) - this is a common prescribing error 5
• Do not delay treatment waiting for laboratory confirmation in high-risk patients with suspected influenza 1
• Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir, and do not use oseltamivir for 14 days after LAIV vaccination 1, 2
• Do not withhold oseltamivir due to mild illness or fever alone - minor febrile illnesses are not contraindications 1