What is the recommended treatment for influenza A?

Treatment for Influenza A

First-Line Treatment

Oseltamivir (Tamiflu) 75 mg orally twice daily for 5 days is the recommended treatment for adults and adolescents ≥13 years with influenza A, initiated as soon as possible and ideally within 48 hours of symptom onset. 1, 2

Timing of Treatment Initiation

• Start treatment immediately for hospitalized patients, those with severe/progressive illness, and high-risk patients, regardless of illness duration 1, 3
• Greatest benefit occurs when initiated within 48 hours of symptom onset, reducing illness duration by approximately 24 hours 1, 4
• Treatment may still be considered beyond 48 hours for hospitalized patients or those with severe illness 3

Pediatric Dosing (≥12 months)

Weight-based dosing for children treated twice daily for 5 days: 5, 1

• ≤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

Infant Dosing (<12 months)

• 9-11 months: 3.5 mg/kg per dose twice daily 5, 1
• 0-8 months: 3 mg/kg per dose twice daily 5, 1
• Preterm infants: Dose adjusted by postmenstrual age (1.0-3.0 mg/kg twice daily) 1

Alternative Antiviral Agents

Zanamivir (Inhaled)

• 10 mg (two 5-mg inhalations) twice daily for 5 days for patients ≥7 years 1, 6
• Acceptable alternative but more difficult to administer 5, 7
• Not recommended for patients with underlying airways disease (asthma, COPD) due to risk of serious bronchospasm 6

Peramivir (IV)

• Recommended for severely ill patients with concerns about oral absorption 1
• Approved for children ≥2 years who are not hospitalized and symptomatic ≤2 days 7

Amantadine and Rimantadine

• Not recommended due to high resistance rates among current influenza A strains 5, 1, 3

Patient Groups Requiring Immediate Treatment

Treatment should be initiated immediately for: 1, 3

• All hospitalized patients with confirmed or suspected influenza
• Patients with severe, progressive, or complicated illness (pneumonia, respiratory failure)
• High-risk patients including:
  • Children <2 years
  • Adults ≥65 years
  • Pregnant and postpartum women
  • Immunocompromised patients
  • Patients with chronic medical conditions

Duration of Treatment

• Standard duration: 5 days 1, 2
• Extended duration may be considered for patients with persistent fever after 6 days, immunocompromised patients, or critically ill patients 1

Renal Dose Adjustment

• For creatinine clearance <30 mL/min, reduce oseltamivir dose by 50% to 75 mg once daily 1
• Not recommended for end-stage renal disease patients not undergoing dialysis 2

Common Side Effects and Management

• Nausea and vomiting occur in 10-15% of patients taking oseltamivir 1, 8
• Taking oseltamivir with food reduces gastrointestinal side effects 1, 2
• Diarrhea may occur in infants <1 year 1, 7
• Neuropsychiatric events have not been definitively linked to oseltamivir 1, 7

Managing Influenza Complications

Secondary Bacterial Pneumonia

• High-risk patients with lower respiratory features should receive antibiotics (co-amoxiclav or tetracycline) 1
• For non-severe influenza-related pneumonia: oral co-amoxiclav or tetracycline, administered within 4 hours of admission 1
• For severe influenza-related pneumonia: IV combination therapy with broad-spectrum β-lactamase stable antibiotic plus macrolide 1

Post-Exposure Prophylaxis

• 75 mg once daily for 10 days, initiated within 48 hours of exposure 1
• Seasonal prophylaxis: 75 mg once daily for up to 6 weeks during community outbreaks 1

Important Clinical Considerations

• Do not delay treatment while awaiting confirmatory test results 7, 3
• Oseltamivir reduces hospitalization rates and subsequent antibiotic use 1, 8
• The drug is generally well tolerated with minimal clinically significant drug interactions 9
• No evidence supports double-dose oseltamivir (150 mg twice daily) for improved outcomes in influenza A 10
• Continuous monitoring of resistance patterns is essential, though most current strains remain susceptible to oseltamivir 5, 7