Recommended Dosage of Tamiflu (Oseltamivir) for Treating Influenza
The recommended dose of Tamiflu (oseltamivir) for treating influenza in adults is 75 mg twice daily for 5 days, while dosing for children varies by weight and age. 1, 2
Adult Dosing
- Adults and adolescents (≥13 years): 75 mg twice daily for 5 days 2, 1
- Administration can be with or without food, though taking with food may improve gastrointestinal tolerability 2, 3
- For patients with renal insufficiency (creatinine clearance 10-30 mL/min): 75 mg once daily for 5 days 2, 3
Pediatric Dosing
Weight-based dosing for children ≥12 months:
Age-based dosing for infants:
- Infants 9-11 months: 3.5 mg/kg per dose twice daily for 5 days 2
- Term infants 0-8 months: 3 mg/kg per dose twice daily for 5 days 2
- Preterm infants: Dosing based on postmenstrual age (gestational age + chronological age) 2, 3
Formulation Information
- Available as Tamiflu in 30 mg, 45 mg, and 75 mg capsules 2, 1
- Also available as powder for oral suspension (6 mg/mL when reconstituted) 2, 1
- If commercial suspension is unavailable, capsules can be opened and mixed with sweetened liquid or a suspension can be compounded by pharmacists 2
Clinical Considerations
- Treatment should be initiated within 48 hours of symptom onset for maximum effectiveness 3, 4
- Early initiation of therapy is associated with faster resolution of symptoms 4
- Standard dosing is effective for both influenza A and B strains, though higher doses may improve virologic response specifically in influenza B infections 5
- No significant benefit has been demonstrated for double-dose oseltamivir therapy in most patient populations 6
- Treatment beyond 48 hours after symptom onset may still be beneficial in critically ill patients with H1N1 influenza requiring ICU admission 6
Common Side Effects
- Gastrointestinal effects (nausea, vomiting, diarrhea) are the most common adverse events 3, 4
- These side effects are typically mild and transient 4
- Taking oseltamivir with food can reduce gastrointestinal side effects 3, 4
The most recent guidelines consistently recommend the standard 75 mg twice daily dose for adults and appropriate weight-based dosing for children, with treatment duration of 5 days for uncomplicated influenza 2, 1. This dosing regimen has been shown to effectively reduce the duration of illness by up to 1.5 days and decrease the severity of symptoms when initiated promptly 4.