What is the recommended treatment for influenza A?

Treatment for Influenza A

The recommended first-line treatment for influenza A is oral oseltamivir (Tamiflu) 75 mg twice daily for 5 days in adults, with weight-based dosing for children, initiated as soon as possible and preferably within 48 hours of symptom onset. 1, 2, 3

Patient Selection for Antiviral Treatment

Antiviral treatment should be started as soon as possible for:

• Hospitalized patients with confirmed or suspected influenza, regardless of illness duration 1
• Patients with severe or progressive illness, regardless of illness duration 1
• High-risk patients including: 1, 2
  • Those with chronic medical conditions or immunocompromised status
  • Children younger than 2 years
  • Adults ≥65 years
  • Pregnant women and those within 2 weeks postpartum

Treatment can be considered for otherwise healthy patients who are not at high risk of complications 1.

First-Line Treatment: Oseltamivir

Dosing for Adults and Children

• Adults and children >40 kg: 75 mg twice daily for 5 days 2, 3
• Children by weight: 2
  • ≤15 kg: 30 mg twice daily

  • 15-23 kg: 45 mg twice daily

  • 23-40 kg: 60 mg twice daily

• Infants <1 year: 1
  • ≤3 months: 12 mg twice daily
  • 3-5 months: 20 mg twice daily
  • 6-11 months: 25 mg twice daily

Clinical Pearls for Oseltamivir

• Most effective when started within 24 hours of symptom onset 4
• Reduces illness duration by approximately 1-1.5 days 5, 6
• Reduces secondary complications (otitis media, bronchitis, pneumonia) 5, 7
• Take with food to reduce gastrointestinal side effects (nausea, vomiting) 7, 4

Alternative Treatments

When oseltamivir cannot be used, consider:

1. Zanamivir (Relenza): 10 mg (two 5-mg inhalations) twice daily for 5 days for patients ≥7 years 2, 8

   • Caution: Contraindicated in patients with underlying respiratory disease due to risk of bronchospasm 2, 8

2. Peramivir (Rapivab): Single IV dose for patients who cannot take oral medication 2

3. Baloxavir (Xofluza): Single oral dose for patients ≥12 years weighing >40 kg 2

Important Timing Considerations

The efficacy of antiviral treatment is time-dependent:

• Treatment within 12 hours of symptom onset reduces illness duration by 74.6 hours (3.1 days) 4
• Treatment within 24 hours reduces illness duration by 53.9 hours compared to starting at 48 hours 4
• Treatment after 48 hours may still be beneficial for hospitalized patients or those with severe disease 1, 9

Management of Complications

• Investigate and empirically treat bacterial coinfections in patients with severe disease (extensive pneumonia, respiratory failure, hypotension, fever) 1
• Consider bacterial coinfection in patients who deteriorate after initial improvement or fail to improve after 3-5 days of antiviral treatment 1
• Investigate other causes besides influenza in patients who fail to improve despite antiviral treatment 1

Special Considerations

• Longer treatment duration may be needed for immunocompromised patients or those hospitalized with severe lower respiratory disease 1
• Consider neuraminidase inhibitor resistance testing for patients who develop influenza while on prophylaxis or who show persistent viral replication despite treatment 1
• Avoid amantadine and rimantadine due to high rates of resistance among circulating influenza strains 1

Early diagnosis and prompt initiation of antiviral therapy are crucial for maximizing treatment benefits and reducing complications of influenza A infection.