What is the first line treatment for influenza?

First-Line Treatment for Influenza

Oral oseltamivir (Tamiflu) is the first-line treatment for influenza in both adults and children, with treatment ideally initiated within 48 hours of symptom onset. 1, 2

Recommended Antiviral Medications

Oseltamivir (First-Line)

• Adults: 75 mg twice daily for 5 days 1
• Children ≥12 months (weight-based dosing):
  • ≤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 2

• Infants 9-11 months: 3.5 mg/kg twice daily 2
• Term infants 0-8 months: 3 mg/kg twice daily 2

Alternative Options

• Zanamivir (Relenza): For patients ≥7 years without chronic respiratory disease
  • 10 mg (two 5-mg inhalations) twice daily for 5 days 2
• Peramivir (Rapivab): For patients ≥2 years who cannot take oral medication
  • Single IV dose for patients with uncomplicated influenza 2
• Baloxavir (Xofluza): For patients ≥12 years weighing >40 kg 1

Treatment Indications and Timing

Priority Populations for Treatment

1. Hospitalized patients with confirmed or suspected influenza 2
2. Patients with severe, complicated, or progressive illness 2
3. High-risk patients including:
   • Children <2 years
   • Adults ≥65 years
   • Pregnant women
   • Individuals with chronic medical conditions 2

Timing of Treatment

• Optimal timing: Within 48 hours of symptom onset 2
• Earlier treatment provides better outcomes: Treatment within 12 hours can reduce illness duration by up to 74.6 hours compared to starting at 48 hours 3
• Treatment after 48 hours: Still beneficial for hospitalized patients or those with severe/progressive disease 2

Evidence on Effectiveness

The most recent evidence shows that oseltamivir treatment:

• Reduces illness duration by approximately 17.6-29.9 hours in children with laboratory-confirmed influenza 2
• Reduces the risk of otitis media by 34% in children 2
• May reduce the risk of hospitalization 2

A meta-analysis of randomized controlled trials showed that treatment with oseltamivir significantly reduced the duration of illness, with greater benefit when children with asthma were excluded (29.9 hours reduction vs. 17.6 hours) 2.

Common Side Effects and Management

• Oseltamivir: Nausea and vomiting (occurs in approximately 5% of treated patients) 2
  • Taking with food can reduce gastrointestinal side effects 4
• Zanamivir: Bronchospasm (contraindicated in patients with underlying respiratory disease) 1

Common Pitfalls to Avoid

1. Delaying treatment while waiting for test results: Treatment should be initiated based on clinical suspicion during influenza season 1
2. Missing the optimal treatment window: Starting treatment after 48 hours significantly reduces effectiveness 4, 3
3. Inappropriate use of antibiotics: Reserve antibiotics for patients with suspected bacterial complications 1
4. Overlooking high-risk patients: These individuals benefit most from antiviral therapy and should be prioritized 2

Testing Considerations

Testing should be performed when results will impact clinical management:

• To inform antiviral treatment decisions
• To avoid unnecessary antibiotic use
• To initiate infection control measures 2

Molecular assays with high sensitivity and specificity are preferred for hospitalized patients 2.

While influenza vaccination remains the best preventive measure, prompt antiviral treatment is essential for reducing morbidity, mortality, and complications in patients with influenza.