What is the recommended treatment for influenza?

Influenza Treatment

For suspected or confirmed influenza, initiate oseltamivir 75 mg orally twice daily for 5 days as soon as possible, ideally within 48 hours of symptom onset, for all high-risk patients and hospitalized patients regardless of illness duration. 1, 2

Who Should Receive Antiviral Treatment

Immediate Treatment Required (Do Not Delay)

• Any hospitalized patient with suspected or confirmed influenza, regardless of how long symptoms have been present 3, 4
• Patients with severe, progressive, or complicated illness including pneumonia or respiratory failure 3, 4
• All high-risk patients including:
  • Children under 2 years of age 3
  • Adults 65 years and older 3
  • Pregnant women and postpartum women (within 2 weeks of delivery) 3
  • Immunocompromised patients 3
  • Patients with chronic conditions: pulmonary (including asthma), cardiovascular (except hypertension alone), renal, hepatic, hematological, metabolic (including diabetes), or neurologic disorders 3
  • Morbidly obese patients (BMI ≥40) 3
  • Nursing home residents 3

Treatment May Be Considered

• Previously healthy outpatients with uncomplicated influenza if treatment can start within 48 hours of symptom onset 3, 5
• Children whose household contacts are under 6 months or have high-risk conditions 5

Antiviral Medication Dosing

Oseltamivir (First-Line Treatment)

Adults and adolescents ≥13 years: 75 mg orally twice daily for 5 days 1, 2, 6

Pediatric dosing (weight-based): 1, 2, 6

• ≤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 <12 months: 2, 6

• 9-11 months: 3.5 mg/kg twice daily
• 0-8 months: 3 mg/kg twice daily
• Preterm infants: dose varies by postmenstrual age (1.0-3.0 mg/kg twice daily)

Renal impairment (CrCl <30 mL/min): Reduce dose to 75 mg once daily 1, 2

Alternative Agents

Zanamivir (inhaled): 10 mg (two 5-mg inhalations) twice daily for 5 days, approved for ages ≥7 years 2, 7

• Contraindicated in patients with airway disease (asthma, COPD) due to risk of severe bronchospasm 1

Peramivir (IV): For severely ill patients with concerns about oral absorption 2

Critical Timing Considerations

• Start treatment immediately without waiting for laboratory confirmation 3, 4
• Greatest benefit within 24 hours of symptom onset, but still effective within 48 hours 3, 1
• Treatment beyond 48 hours is still recommended for hospitalized patients, severe disease, or high-risk patients 3
• Do not delay for diagnostic testing - empiric treatment is appropriate when influenza is suspected 3, 4

Duration of Treatment

• Standard duration: 5 days for most patients 1, 2, 6
• Consider longer duration for immunocompromised patients, critically ill patients, or those with persistent fever after 6 days 2, 4

Managing Complications with Antibiotics

When to Add Antibiotics

Add antibiotics when bacterial coinfection is suspected: 3, 2, 4

• Severe initial presentation
• Clinical deterioration after initial improvement
• Failure to improve after 3-5 days of antiviral treatment
• Worsening symptoms (recrudescent fever or increasing dyspnea) 3

Antibiotic Selection

Non-severe influenza-related pneumonia: 3, 2

• Oral co-amoxiclav or tetracycline preferred
• Macrolide (clarithromycin) or fluoroquinolone as alternative

Severe influenza-related pneumonia: 3, 2, 4

• IV combination therapy: broad-spectrum β-lactamase stable antibiotic (co-amoxiclav or cephalosporin) PLUS macrolide
• Administer within 4 hours of admission 3
• Target likely pathogens: S. pneumoniae, S. aureus (including MRSA), S. pyogenes 3

Previously healthy adults with acute bronchitis: Do not routinely require antibiotics unless worsening symptoms develop 3, 2

Common Pitfalls and Adverse Effects

• Nausea and vomiting occur in 10-15% of patients taking oseltamivir; taking with food reduces gastrointestinal side effects 1, 2
• Do not use adamantanes (amantadine, rimantadine) due to high resistance rates 2
• Avoid corticosteroids for influenza treatment unless indicated for other reasons, as they increase mortality risk and bacterial superinfection 4, 8
• Do not use zanamivir dry powder via nebulization in intubated patients - associated with ventilator malfunction 8

Prophylaxis Dosing

Post-exposure prophylaxis: Oseltamivir 75 mg once daily for 10 days, initiated within 48 hours of exposure 1, 2, 6

Seasonal prophylaxis: Oseltamivir 75 mg once daily for up to 6 weeks during community outbreaks 1, 2, 6

Immunocompromised patients: May continue prophylaxis for up to 12 weeks 6

Monitoring for Resistance

Monitor for antiviral resistance in: 4

• Patients developing influenza while on or immediately after prophylaxis
• Immunocompromised patients with persistent viral replication
• Patients with severe influenza not improving with treatment