Oseltamivir Treatment for Influenza A and B
Oseltamivir is recommended at a dosage of 75 mg twice daily for 5 days in adults for the treatment of influenza A and B, with weight-based dosing for children. 1, 2
Adult Dosing
- 75 mg twice daily for 5 days for treatment 1
- 75 mg once daily for 10 days for prophylaxis 1
- Treatment should be initiated within 48 hours of symptom onset for maximum efficacy 3, 4
Pediatric Dosing (Treatment)
For children ≥12 months (based on weight):
- ≤15 kg (≤33 lb): 30 mg twice daily for 5 days 1
15-23 kg (33-51 lb): 45 mg twice daily for 5 days 1
23-40 kg (51-88 lb): 60 mg twice daily for 5 days 1
40 kg (>88 lb): 75 mg twice daily for 5 days 1
Infant Dosing (Treatment)
- 9-11 months: 3.5 mg/kg per dose twice daily for 5 days 1
- 0-8 months: 3 mg/kg per dose twice daily for 5 days 1
Preterm Infant Dosing
Based on postmenstrual age:
- <38 weeks postmenstrual age: 1.0 mg/kg twice daily 1
- 38-40 weeks postmenstrual age: 1.5 mg/kg twice daily 1
40 weeks postmenstrual age: 3.0 mg/kg twice daily 1
- For extremely preterm infants (<28 weeks), consultation with a pediatric infectious disease specialist is recommended 1
Special Considerations
- Oseltamivir can be taken with or without food, though administration with food may improve gastrointestinal tolerability 1, 3
- For patients with renal impairment (creatinine clearance 10-30 mL/min): 75 mg once daily for 5 days for treatment 1
- Available as capsules (30 mg, 45 mg, and 75 mg) and as powder for oral suspension (6 mg/mL) 1, 3
Clinical Efficacy
- Oseltamivir reduces the duration of influenza illness by up to 1.5 days when started within 36 hours of symptom onset 5
- Earlier initiation of therapy (within 12-24 hours) is associated with greater reduction in illness duration 4
- Treatment significantly reduces the incidence of secondary complications such as otitis media, bronchitis, pneumonia, and sinusitis 5, 4
- A recent study showed 82% reduction in odds of in-patient death with standard oseltamivir treatment compared to no treatment in hospitalized patients with confirmed influenza 6
Antiviral Activity
- Effective against both influenza A and B viruses 1, 7
- Current circulating influenza A (H3N2) and B virus strains remain susceptible to oseltamivir with rare exceptions 1
- No significant differences in viral clearance rates between standard dose (75 mg) and higher dose (150 mg) regimens for influenza A, though higher doses may improve virologic response in influenza B 8
Key Clinical Pearls
- Treatment should be initiated as soon as possible after symptom onset, ideally within 48 hours 3, 4
- Earlier treatment (within 12-24 hours) provides significantly greater benefits than delayed treatment 4
- Resistance to oseltamivir remains rare and appears to have limited clinical impact due to reduced transmissibility of resistant strains 4
- For prophylaxis, oseltamivir is given as 75 mg once daily for 10 days following exposure 1