Recommended Use and Dosage of Oseltamivir (Tamiflu) for Influenza
Oseltamivir is recommended for treatment of influenza in patients when started within 48 hours of symptom onset, with a standard adult dosage of 75 mg twice daily for 5 days, and weight-based dosing for children. 1, 2
Adult Dosing
- For treatment of influenza: 75 mg twice daily for 5 days 1, 2
- For prophylaxis of influenza: 75 mg once daily for at least 10 days following close contact with an infected individual, and up to 6 weeks during a community outbreak 1, 2
- No dosage adjustment needed based on age alone for elderly patients 1
Pediatric Dosing
Children ≥1 year (treatment for 5 days):
- ≤15 kg: 30 mg twice daily 1
15-23 kg: 45 mg twice daily 1
23-40 kg: 60 mg twice daily 1
40 kg: 75 mg twice daily 1
Children ≥1 year (prophylaxis):
- Same weight-based dosing as treatment, but administered once daily instead of twice daily 1
Infants <1 year:
- 3 mg/kg twice daily for treatment 1
- Not recommended for prophylaxis in infants <3 months unless situation is critical 1
- For infants 3-11 months: 3 mg/kg once daily for prophylaxis 1
Special Populations
Renal Impairment
- For patients with creatinine clearance 10-30 mL/min: reduce treatment dosage to 75 mg once daily and prophylaxis dosage to 75 mg every other day 1, 3
- Not recommended for patients with end-stage renal disease not undergoing dialysis 2
Timing of Administration
- Treatment should be initiated within 48 hours of symptom onset for maximum effectiveness 1, 4
- Earlier initiation (within 24 hours) results in greater reduction of symptom duration 4
Clinical Benefits
- Reduces duration of influenza symptoms by approximately 29-36 hours (25-30%) in otherwise healthy adults 5, 4
- In high-risk populations (those with chronic respiratory or cardiac diseases), oseltamivir reduces symptom duration by 36.8% and severity by 43.1% 6
- Reduces incidence of secondary complications and antibiotic use in both healthy and high-risk patients 5, 6
Formulations and Administration
- Available as capsules (30 mg, 45 mg, and 75 mg) and oral suspension (6 mg/mL) 3, 2
- Can be taken with or without food, though taking with food may improve gastrointestinal tolerability 3, 2
- If commercial oral suspension is unavailable, capsules can be opened and mixed with sweetened liquid 1
Common Side Effects and Precautions
- Most common adverse events are nausea and vomiting, which are generally mild and transient 5, 7
- Gastrointestinal events are less likely when oseltamivir is taken with food 5
- No benefit has been demonstrated for double-dose oseltamivir (150 mg twice daily) compared to standard dose in patients with severe influenza 8
Prophylaxis Considerations
- Protective efficacy of 74-87% when used for seasonal prophylaxis 7
- For institutional outbreaks, chemoprophylaxis should be administered to all eligible residents for a minimum of 2 weeks, and continued until approximately 7-10 days after illness onset in the last patient 1
Oseltamivir remains a key antiviral medication for both treatment and prophylaxis of influenza, with established efficacy in reducing symptom duration and complications when initiated promptly after symptom onset.