What is the recommended treatment for Influenza A?

Treatment for Influenza A

Start oseltamivir 75 mg orally twice daily for 5 days immediately for any patient with confirmed or suspected influenza A who is hospitalized, severely ill, or at high risk for complications, regardless of symptom duration. 1, 2, 3

Who Requires Immediate Antiviral Treatment

Mandatory treatment groups where therapy should never be delayed:

• All hospitalized patients with confirmed or suspected influenza A 4, 1
• Patients with severe, progressive, or complicated illness (pneumonia, respiratory failure) at any point in their disease course 4, 2
• Patients requiring ICU admission 2

High-risk outpatients who should receive treatment when presenting within 48 hours of symptom onset:

• Children <2 years (especially infants <6 months who have highest mortality) 4, 1
• Adults ≥65 years 4, 2
• Pregnant women and postpartum women (within 2 weeks of delivery) 4, 2
• Immunocompromised patients (HIV, medications, transplant recipients) 4, 2
• Patients with chronic medical conditions (asthma, COPD, heart disease, diabetes, neurologic disorders, obesity) 4, 1

First-Line Treatment: Oseltamivir

Adult and adolescent dosing (≥13 years):

• 75 mg orally twice daily for 5 days 1, 3
• Take with food to reduce gastrointestinal side effects 1

Pediatric dosing (weight-based for ages 1-12 years):

• ≤15 kg: 30 mg twice daily 1, 3
• 15.1-23 kg: 45 mg twice daily 1, 3
• 23.1-40 kg: 60 mg twice daily 1, 3

• 40 kg: 75 mg twice daily 1, 3

Infant dosing (<12 months):

• 9-11 months: 3.5 mg/kg per dose twice daily 1
• 0-8 months: 3 mg/kg per dose twice daily 1
• Preterm infants require specialized dosing based on postmenstrual age 1

Alternative Antiviral Agents

Zanamivir (inhaled):

• 10 mg (two 5-mg inhalations) twice daily for 5 days 1, 5
• Approved for ages ≥7 years for treatment 5
• Critical contraindication: Do not use in patients with underlying airways disease (asthma, COPD) due to risk of serious bronchospasm 5

Peramivir (IV):

• Reserved for severely ill patients with concerns about oral or inhaled drug absorption 1

Amantadine and rimantadine:

• Not recommended due to high resistance rates (>99%) among current influenza A strains 1, 2

Critical Timing Considerations

The 48-hour window applies differently based on patient risk:

• For high-risk and hospitalized patients: Treat immediately regardless of time since symptom onset, even if >48 hours 4, 2
• For previously healthy outpatients: Greatest benefit when started within 48 hours, but can still consider treatment based on clinical judgment 4
• Do not delay treatment while awaiting laboratory confirmation in high-risk or severely ill patients 4

Expected Clinical Benefits

When started within 48 hours in outpatients:

• Reduces illness duration by approximately 24 hours 1, 6
• May decrease hospitalization rates 1
• May reduce need for subsequent antibiotics 1
• Reduces otitis media in children 7

In hospitalized patients:

• Early treatment associated with reduced mortality 7
• Earlier hospital discharge when initiated within 2 days of symptom onset 8

Managing Bacterial Coinfection

Add empiric antibiotics in addition to oseltamivir when patients present with:

• Initial severe disease at presentation 2
• Clinical deterioration after initial improvement 2
• Failure to improve after 3-5 days of antiviral treatment 2

Antibiotic selection should target common influenza-associated pathogens:

• Streptococcus pneumoniae, Streptococcus pyogenes, and Staphylococcus aureus (including MRSA) 4
• For non-severe pneumonia: oral co-amoxiclav or tetracycline 1
• For severe pneumonia: IV combination therapy with broad-spectrum β-lactamase stable antibiotic plus macrolide 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 on dialysis 3

Extended Treatment Duration

Consider treatment beyond 5 days for:

• Patients with persistent fever after 6 days 1
• Immunocompromised patients 1
• Critically ill patients 1

Common Pitfalls and Side Effects

Gastrointestinal effects:

• Nausea and vomiting occur in 10-15% of patients 1
• Taking oseltamivir with food significantly reduces these side effects 1
• Diarrhea may occur in infants <1 year 1

What NOT to do:

• Do not use corticosteroids as adjunctive therapy for seasonal influenza—associated with increased mortality and bacterial superinfection 2, 7
• Do not withhold treatment in severely ill patients presenting >48 hours after symptom onset 4, 2
• Do not delay treatment while awaiting test results in high-risk patients 4

Prophylaxis Dosing

Post-exposure prophylaxis (within 48 hours of exposure):

• 75 mg once daily for 10 days 1, 3

Seasonal prophylaxis during community outbreaks:

• 75 mg once daily for up to 6 weeks 1, 3
• May extend to 12 weeks in immunocompromised patients 3