Recommended Treatment for Influenza
Oral oseltamivir (Tamiflu) remains the antiviral drug of choice for the management of illness caused by influenza virus infections. 1 Inhaled zanamivir (Relenza) is an equally acceptable alternative for patients who do not have chronic respiratory disease.
First-Line Treatment Options
Oseltamivir (Tamiflu)
- Dosing for adults: 75 mg twice daily for 5 days
- Dosing for children ≥12 months (based on weight):
- ≤15 kg: 30 mg twice daily
15-23 kg: 45 mg twice daily
23-40 kg: 60 mg twice daily
40 kg: 75 mg twice daily
- Infants 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: Dosing varies by postmenstrual age 1
Zanamivir (Relenza)
- Adults and children ≥7 years: 10 mg (two 5-mg inhalations) twice daily for 5 days 1, 2
- Important limitation: Not recommended for individuals with underlying airways disease (such as asthma or COPD) due to risk of serious bronchospasm 2
Timing of Treatment
Treatment should be initiated as soon as possible after symptom onset, ideally within 48 hours, as this maximizes effectiveness:
- When administered within 2 days of illness onset, these antivirals can reduce the duration of uncomplicated influenza illness by approximately 1 day 1
- Earlier initiation of therapy is associated with faster resolution of symptoms 3
- For patients with severe, complicated, or progressive illness, treatment should be offered regardless of time since symptom onset 1
Special Populations
High-Risk Patients
Treatment should be offered as early as possible, regardless of influenza immunization status and whether onset of illness has been <48 hours, for:
- Any hospitalized patient with presumed influenza
- Patients with severe, complicated, or progressive illness
- Patients at high risk of complications (including those with chronic medical conditions) 1
Children
- Oseltamivir is approved for treatment in children ≥1 year old
- Zanamivir is approved for treatment in children ≥7 years old 1
- For children who cannot tolerate oral medication, IV peramivir is approved for children ≥2 years old 1
Clinical Benefits and Limitations
Established Benefits
- Reduction in duration of symptoms and fever by approximately 1 day 1, 4
- Reduction in severity of illness by up to 38% compared with placebo 3
- Reduced incidence of secondary complications and antibiotic use 3, 5
Important Limitations
- None of these agents has been definitively demonstrated to prevent serious influenza-related complications such as bacterial pneumonia or exacerbation of chronic diseases in randomized controlled trials 1
- The effectiveness in preventing serious outcomes is supported primarily by observational data 1
- Treatment efficacy is best established in otherwise healthy adults with uncomplicated influenza 1
Common Pitfalls to Avoid
Delayed treatment: Effectiveness decreases significantly when treatment is delayed beyond 48 hours after symptom onset, though patients with severe disease may still benefit from later treatment 1, 6
Inappropriate use in patients with respiratory disease: Zanamivir can cause bronchospasm in patients with underlying respiratory conditions such as asthma or COPD 2
Overreliance on antivirals: Antiviral agents should be considered an adjunct to, not a substitute for, vaccination 1
Gastrointestinal side effects: Nausea and vomiting are common with oseltamivir but can be minimized by taking the medication with food 3
Premature discontinuation: Treatment should be continued for the full 5-day course to maximize effectiveness and reduce the risk of viral resistance 1
Prophylaxis Considerations
For prevention of influenza in exposed individuals:
- Oseltamivir: 75 mg once daily for 10 days
- Zanamivir: 10 mg (two 5-mg inhalations) once daily for 10 days 1
Prophylaxis should be considered for high-risk individuals with significant exposure to influenza, but should not replace vaccination as the primary preventive strategy 1.