Tamiflu (Oseltamivir) Dosing and Administration
Treatment Dosing
For adults and adolescents ≥13 years, administer oseltamivir 75 mg orally twice daily for 5 days, initiated within 48 hours of symptom onset for maximum effectiveness. 1, 2
Adults and Adolescents (≥13 years)
- Standard dose: 75 mg orally twice daily for 5 days 1, 2
- Treatment must be started within 48 hours of symptom onset 3, 4
Pediatric Patients (≥12 months to 12 years)
Weight-based dosing twice daily for 5 days: 1, 2
- ≤15 kg (≤33 lb): 30 mg twice daily
15-23 kg (>33-51 lb): 45 mg twice daily
23-40 kg (>51-88 lb): 60 mg twice daily
40 kg (>88 lb): 75 mg twice daily
Infants (0-11 months)
Age-based dosing twice daily for 5 days: 1
- 9-11 months: 3.5 mg/kg per dose twice daily
- Term infants 0-8 months: 3 mg/kg per dose twice daily
Preterm Infants
Postmenstrual age-based dosing (gestational age + chronological age) twice daily for 5 days: 1, 3
- <38 weeks: 1.0 mg/kg twice daily
- 38-40 weeks: 1.5 mg/kg twice daily
40 weeks: 3.0 mg/kg twice daily
Prophylaxis Dosing
Post-Exposure Prophylaxis
Initiate within 48 hours of contact with infected individual: 1, 2
- Adults/adolescents ≥13 years: 75 mg once daily for 10 days 1
- Pediatric patients ≥1 year: Same weight-based doses as treatment, but once daily for 10 days 1
- Infants 3-11 months: 3 mg/kg once daily for 10 days 1
- Prophylaxis is NOT recommended for infants <3 months unless critical situation 3
Seasonal Prophylaxis
- Duration: Up to 6 weeks during community outbreak 2
- Immunocompromised patients: May continue up to 12 weeks 2
Renal Impairment Adjustments
For creatinine clearance 10-30 mL/min: 1, 3
- Treatment: 75 mg once daily for 5 days
- Prophylaxis: 30 mg once daily for 10 days OR 75 mg every other day for 10 days (5 total doses)
Not recommended for end-stage renal disease patients not on dialysis 2
Formulations and Administration
Available Forms
Suspension Dosing Volumes
- 30 mg dose = 5 mL
- 45 mg dose = 7.5 mL
- 60 mg dose = 10 mL
- 75 mg dose = 12.5 mL
Administration Instructions
- Can be taken with or without food 3, 4, 2
- Taking with food improves gastrointestinal tolerability and reduces nausea/vomiting 3, 4
- Capsules can be opened and mixed with liquid if patient cannot swallow whole 3
- If commercial suspension unavailable, pharmacies can compound from capsules to 6 mg/mL concentration 3
Special Populations
Pregnancy and Breastfeeding
- Pregnant women receive same dosing as non-pregnant adults: 75 mg twice daily for 5 days 1
- Safe throughout all trimesters and postpartum period (within 2 weeks after delivery) 1
- Breastfeeding mothers can receive oseltamivir; not a reason to discontinue breastfeeding 1
Critical Drug Interactions
Avoid live attenuated influenza vaccine (LAIV) within 48 hours before oseltamivir use 1, 3
Do not use oseltamivir for 14 days after LAIV vaccination 1, 3
Common Adverse Effects
- Nausea and vomiting (5-15% of patients) 3, 5
- Gastrointestinal effects including diarrhea 3
- Headache and skin reactions may occur 3
- Effects are typically mild and transient 5
Clinical Pearls
- Earlier initiation of therapy (within 48 hours) associated with faster symptom resolution 4, 5
- Treatment reduces illness duration by up to 1.5 days and severity by up to 38% 5
- Reduces secondary complications and antibiotic use 5
- Higher doses (150 mg twice daily) show no additional benefit for influenza A but may improve response in influenza B 6