What is the recommended treatment for influenza (flu)?

Treatment for Influenza

Oseltamivir 75 mg orally twice daily for 5 days is the first-line treatment for influenza and should be initiated within 48 hours of symptom onset, though treatment can still benefit patients with severe illness even beyond this window. 1, 2, 3

When to Initiate Antiviral Treatment

Mandatory treatment groups include: 2, 4

• All hospitalized patients with suspected or confirmed influenza
• Patients with severe, complicated, or progressive illness
• High-risk patients: children under 2 years, adults ≥65 years, pregnant/postpartum women (within 2 weeks of delivery), immunocompromised individuals, and those with chronic medical conditions (pulmonary, cardiac, renal, metabolic diseases) 1, 2

Optional treatment for previously healthy outpatients presenting within 48 hours of symptom onset, based on clinical judgment 4

Key timing principle: Treatment started within 24 hours provides maximum benefit, reducing symptom duration by approximately 1 day in healthy patients and potentially reducing complications and mortality in high-risk groups 1, 2, 5

Antiviral Medication Dosing

Oseltamivir (Preferred Agent)

Adults and adolescents ≥13 years: 75 mg orally twice daily for 5 days 1, 3

Pediatric dosing (weight-based): 1, 3

• ≤15 kg: 30 mg twice daily
• 15.1-23 kg: 45 mg twice daily
• 23.1-40 kg: 60 mg twice daily

• 40 kg: 75 mg twice daily

• Infants 0-8 months: 3 mg/kg per dose twice daily
• Infants 9-11 months: 3.5 mg/kg per dose twice daily

Renal adjustment: Reduce dose by 50% (75 mg once daily) if creatinine clearance <30 mL/min 1, 3

Alternative Agents

Zanamivir (inhaled): 10 mg (two 5-mg inhalations) twice daily for 5 days in patients ≥7 years; avoid in patients with asthma or chronic respiratory disease due to bronchospasm risk 1, 6

Peramivir (IV): Single 600 mg dose for adults or 12 mg/kg (max 600 mg) for children 2-12 years; limited to acute uncomplicated influenza in non-hospitalized patients symptomatic ≤2 days 1

Baloxavir: Single oral dose (40 mg for 40-80 kg, 80 mg for ≥80 kg) in patients ≥12 years 1

Treatment Beyond 48 Hours

Severely ill or hospitalized patients should receive oseltamivir regardless of symptom duration, as treatment initiated even after 48 hours may reduce mortality and complications, particularly when started within 5 days of symptom onset 1, 2, 4

Patients unable to mount adequate febrile response (immunocompromised, very elderly) remain eligible for treatment despite lack of documented fever 1

Antibiotic Management

Antibiotics are NOT routinely indicated for uncomplicated influenza, as this is a viral illness 1, 4

Consider antibiotics when: 1, 4

• Worsening symptoms develop (recrudescent fever, increasing dyspnea)
• Influenza-related pneumonia is present
• High-risk patients develop lower respiratory tract features

Antibiotic selection for influenza-related pneumonia: 1

• Non-severe pneumonia: Oral co-amoxiclav or doxycycline; macrolide (clarithromycin) or fluoroquinolone as alternative
• Severe pneumonia: IV co-amoxiclav or 2nd/3rd generation cephalosporin (cefuroxime, cefotaxime) PLUS macrolide (clarithromycin or erythromycin)
• Duration: 7 days for uncomplicated pneumonia, 10 days for severe pneumonia, 14-21 days if S. aureus or Gram-negative bacteria suspected

Prophylactic Use

Oseltamivir prophylaxis (75 mg once daily for 10 days) is indicated for: 1, 2, 3

• Unvaccinated high-risk individuals with close contact to infected persons (initiate within 48 hours of exposure)
• Household contacts of high-risk patients during outbreaks
• Institutional outbreak control (can extend up to 6 weeks during community outbreaks)
• Immunocompromised patients (may continue up to 12 weeks)

Prophylaxis does NOT replace vaccination and should be used as an adjunct only 1, 2

Common Pitfalls

• Vomiting occurs in approximately 15% of oseltamivir-treated children versus 9% with placebo; taking medication with food improves tolerability 1, 3
• Do not use double-dose oseltamivir as no benefit has been demonstrated over standard dosing 1
• Zanamivir contraindicated in patients with underlying airway disease due to severe bronchospasm risk 1, 6
• Peramivir efficacy not established for hospitalized patients with serious influenza 1