What are the guidelines for antiviral therapy in respiratory infections, including influenza, Respiratory Syncytial Virus (RSV) infection, and SARS-CoV-2 infection?

Guidelines for Antiviral Therapy in Respiratory Infections

Antiviral therapy should be initiated as early as possible for influenza, RSV, and SARS-CoV-2 infections, with specific agents selected based on the identified pathogen and patient risk factors.

Influenza Antiviral Therapy

Treatment Recommendations

• Oral oseltamivir is the antiviral drug of choice for influenza infections 1

  • Adults: 75 mg twice daily for 5 days
  • Children (based on weight):
    • ≤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

  • Reduce to 75 mg once daily if creatinine clearance <30 ml/min 2

• Inhaled zanamivir is an acceptable alternative for patients without chronic respiratory disease 1

• Intravenous peramivir is approved for acute uncomplicated influenza in children ≥2 years who are not hospitalized and symptomatic for ≤2 days 1

Timing and Indications

• Treatment should be offered as early as possible (ideally within 48 hours of symptom onset) for:

  • Any hospitalized patient with suspected influenza 1
  • Patients with severe, complicated, or progressive illness 1
  • Patients at high risk of complications (children <5 years, adults ≥65 years, pregnant women, immunocompromised, chronic medical conditions) 1, 2

• Treatment may be considered for otherwise healthy individuals with influenza-like illness 1

Prophylaxis

• Oseltamivir is approved for chemoprophylaxis in persons ≥13 years 1
• Consider prophylaxis for:
  • Unvaccinated healthcare personnel in contact with influenza patients 1
  • All healthcare personnel if outbreak is caused by a variant not well-matched by vaccine 1
  • High-risk patients exposed to influenza 1

COVID-19 (SARS-CoV-2) Antiviral Therapy

Treatment Recommendations

• Remdesivir is indicated for COVID-19 treatment in:
  • Hospitalized adults and pediatric patients (birth to <18 years weighing ≥1.5 kg) 3
  • Non-hospitalized patients with mild-to-moderate COVID-19 at high risk for progression to severe disease 3

Management Considerations

• Follow local health authority guidelines for vaccination and treatment 1
• Temporary discontinuation of ongoing therapies may be needed until clinical resolution and RT-PCR clearance 1
• Consider drug interactions when selecting therapy 1

RSV Antiviral Therapy

• Limited antiviral options are available for RSV
• Treatment is primarily supportive care
• For high-risk patients (immunocompromised, elderly, infants), consider early consultation with infectious disease specialists 4

Monitoring During Antiviral Therapy

Clinical Monitoring

• Monitor vital signs at least twice daily: temperature, respiratory rate, pulse, blood pressure, mental status, oxygen saturation 2
• Use Early Warning Score systems for efficient monitoring 2
• Failure to improve clinically within 48 hours should prompt reassessment 1
• Repeat chest radiograph if no improvement after 4 days 1

Laboratory Monitoring

• Perform diagnostic testing to confirm the specific viral pathogen:
  • Rapid influenza testing for suspected influenza 1
  • PCR testing of respiratory specimens for SARS-CoV-2 1
  • Viral cultures may be needed to determine influenza subtype 1

Special Considerations

Antiviral Resistance

• Monitor for emergence of resistant strains
• If local surveillance data indicate resistance patterns, adjust empiric therapy accordingly 1
• Amantadine and rimantadine should not be used for influenza due to high resistance levels 1

Hospitalized Patients

• For severe illness requiring hospitalization:
  • Consider higher doses or extended duration of antivirals 1
  • Immunocompromised patients may benefit from treatment started >48 hours from onset 1
  • Intravenous formulations may be preferred for patients unable to take oral medications 5

Infection Control Measures

• During outbreaks:
  • Restrict visitors with influenza-like illness 1
  • Consider curtailing elective admissions 1
  • Evaluate healthcare personnel with influenza-like illness for removal from direct patient contact 1

Common Pitfalls to Avoid

1. Delayed initiation of antiviral therapy - Effectiveness decreases significantly after 48 hours of symptom onset
2. Inappropriate antibiotic use - Antibiotics are not effective against viral infections unless bacterial co-infection is suspected
3. Failure to adjust dosing in renal impairment - Particularly important for oseltamivir
4. Overlooking high-risk patients - Early treatment is crucial for those at risk of complications
5. Relying solely on clinical diagnosis - Laboratory confirmation helps guide appropriate therapy

By following these guidelines, clinicians can optimize antiviral therapy for respiratory infections, potentially reducing morbidity, mortality, and complications in affected patients.