What is the treatment guideline for outpatient community-acquired pneumonia (CAP)?

Treatment Guidelines for Outpatient Community-Acquired Pneumonia

For outpatient community-acquired pneumonia (CAP), treatment should be stratified based on patient comorbidities, with specific antibiotic regimens tailored to each category of patient. 1

Treatment Algorithm for Outpatient CAP

For Healthy Adults Without Comorbidities:

• First choice: Amoxicillin 1 g three times daily (strong recommendation, moderate quality evidence) 1
• Alternative options:
  • Doxycycline 100 mg twice daily (conditional recommendation, low quality evidence) 1
  • Macrolide (only in areas with pneumococcal resistance to macrolides <25%):
    • Azithromycin 500 mg on first day then 250 mg daily, or
    • Clarithromycin 500 mg twice daily, or
    • Clarithromycin extended release 1,000 mg daily 1

For Adults With Comorbidities:

Comorbidities include: chronic heart, lung, liver, or renal disease; diabetes mellitus; alcoholism; malignancy; or asplenia 1

Option 1: Combination therapy (strong recommendation, moderate quality evidence):

• β-lactam:
  • Amoxicillin/clavulanate (500/125 mg three times daily, 875/125 mg twice daily, or 2,000/125 mg twice daily), OR
  • Cephalosporin (cefpodoxime 200 mg twice daily or cefuroxime 500 mg twice daily)
• PLUS one of:
  • Macrolide (azithromycin 500 mg on first day then 250 mg daily, clarithromycin 500 mg twice daily, or clarithromycin extended release 1,000 mg daily), OR
  • Doxycycline 100 mg twice daily

Option 2: Monotherapy with respiratory fluoroquinolone (strong recommendation, moderate quality evidence):

• Levofloxacin 750 mg daily, OR
• Moxifloxacin 400 mg daily, OR
• Gemifloxacin 320 mg daily 1

Key Considerations

Pathogen Coverage

• Most outpatient CAP is caused by Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, and Chlamydophila pneumoniae 2, 3
• Macrolides provide coverage for atypical pathogens but should be used as monotherapy only in areas with low pneumococcal resistance 1

Duration of Therapy

• For most outpatients with CAP, a 5-day course is sufficient if clinical improvement occurs 1
• Azithromycin can be given as a 3-day course (500 mg once daily) due to its long half-life 2, 4

Special Considerations

1. Antibiotic Resistance:

   • Local resistance patterns should guide therapy
   • Macrolide monotherapy should be avoided in areas with pneumococcal resistance ≥25% 1
   • Reserve respiratory fluoroquinolones for patients with comorbidities to minimize resistance development 1

2. First Dose Considerations:

   • Some experts recommend that the first dose of oral doxycycline be 200 mg to achieve adequate serum levels more rapidly 1

3. Risk Stratification:

   • CRB-65 (confusion, respiratory rate, blood pressure, 65 years of age) is a validated tool for risk assessment in primary care settings 5
   • Patients with higher scores may need hospitalization rather than outpatient treatment

Common Pitfalls to Avoid

1. Overuse of fluoroquinolones:

   • Reserve for patients with comorbidities to prevent resistance development 1
   • Be aware of potential adverse effects including tendinopathy and QT prolongation

2. Inadequate coverage for likely pathogens:

   • Ensure coverage for both typical and atypical pathogens, especially in patients with comorbidities 1

3. Inappropriate macrolide monotherapy:

   • Avoid in areas with high pneumococcal resistance to macrolides 1

4. Treating viral pneumonia with antibiotics:

   • Consider testing for viral pathogens during influenza season or COVID-19 pandemic 6

5. Failure to recognize patients who require hospitalization:

   • Use severity assessment tools to identify patients who may need inpatient care 1

The evidence strongly supports a stratified approach to outpatient CAP treatment based on patient characteristics and local resistance patterns, with amoxicillin as first-line therapy for healthy adults and either combination therapy or respiratory fluoroquinolone monotherapy for those with comorbidities 1.