Tamiflu (Oseltamivir) Indications
Tamiflu (oseltamivir) is indicated for the treatment of acute, uncomplicated influenza A and B in patients 2 weeks of age and older who have been symptomatic for no more than 48 hours, and for prophylaxis of influenza A and B in patients 1 year and older. 1
Treatment Indications
Primary Treatment Indications
- Treatment of acute, uncomplicated influenza A and B infection in:
Clinical Benefits of Treatment
- Reduces duration of uncomplicated influenza illness by approximately 1 day compared to placebo 3
- Decreases severity of symptoms by up to 38% 4
- Reduces risk of secondary complications such as otitis media in children 3
- May reduce risk of pneumonia by approximately 50% among influenza-infected patients 3
- May reduce hospital admissions, particularly in high-risk patients 3
Prophylaxis Indications
Primary Prophylaxis Indications
- Post-exposure prophylaxis following close contact with infected individuals 1
- Seasonal prophylaxis during community outbreaks 1
- Prophylaxis in institutional settings during outbreaks 3
Specific Prophylaxis Scenarios
- For unvaccinated individuals during influenza season 5
- For vaccinated high-risk patients as adjunctive protection 5
- For household contacts of infected persons when administered within 48 hours of symptom onset in the index case 4
- During institutional outbreaks (nursing homes, hospitals) 3
Dosing Considerations
Treatment Dosing
- Adults and adolescents (≥13 years): 75 mg twice daily for 5 days
- Children (by weight):
- ≤15 kg: 30 mg twice daily for 5 days
15-23 kg: 45 mg twice daily for 5 days
23-40 kg: 60 mg twice daily for 5 days
40 kg: 75 mg twice daily for 5 days
- Infants 9-11 months: 3.5 mg/kg twice daily for 5 days
- Infants 0-8 months: 3 mg/kg twice daily for 5 days 3, 2
Prophylaxis Dosing
- Adults and adolescents: 75 mg once daily
- Duration: 7 days after last known exposure or 10 days for household prophylaxis
- For institutional outbreaks: minimum of 14 days and up to 6 weeks during community outbreaks 3, 1
Special Populations
Renal Impairment
- Dose adjustment required for patients with renal insufficiency:
- Creatinine clearance 30-60 mL/min: 30 mg twice daily for treatment
- Creatinine clearance 10-30 mL/min: 30 mg once daily for treatment 1
- Not recommended for patients with end-stage renal disease not undergoing dialysis 1
Preterm Infants
- Dosing based on postmenstrual age:
- <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 3
Important Clinical Considerations
Timing of Treatment
- Earlier treatment provides greater benefit - ideally within 12 hours of symptom onset 6
- Treatment initiated within first 24 hours can significantly reduce duration and severity of symptoms 2
- Benefits still observed when treatment is started within 48 hours of symptom onset 3
- Some benefit may still be seen in hospitalized elderly patients even when started >48 hours after symptom onset 3
Limitations and Precautions
- Not a substitute for annual influenza vaccination 1
- Consider current influenza drug susceptibility patterns when deciding whether to use 1
- Take with food to reduce gastrointestinal side effects 2
- Most common adverse events are nausea and vomiting 1
- Monitor for neuropsychiatric events, particularly in pediatric patients 1
Viral Resistance Considerations
- Resistance to oseltamivir can develop but appears less frequent than with older antivirals like amantadine 3
- Development of resistance during treatment has been identified but is uncommon in immunocompetent patients 3
- Higher frequency of resistance has been reported in some pediatric studies 3
By initiating treatment early and following appropriate dosing guidelines, oseltamivir can effectively reduce the duration and severity of influenza illness while potentially preventing serious complications that could lead to increased morbidity and mortality.