What are the recommended empiric antibiotics for community-acquired pneumonia?

Empiric Antibiotics for Community-Acquired Pneumonia

For community-acquired pneumonia (CAP), empiric antibiotic selection should be based on severity of illness, with amoxicillin or amoxicillin-clavulanate plus a macrolide for mild-moderate cases, and a beta-lactam (ceftriaxone, cefotaxime, or ampicillin-sulbactam) plus a macrolide for severe cases requiring hospitalization. 1

Outpatient Treatment (Mild-Moderate CAP)

First-line options:

• Mild CAP without comorbidities:

  • Macrolide (clarithromycin preferred over azithromycin due to fewer cardiovascular adverse events) 2, 1
  • Doxycycline (alternative for patients ≥8 years old) 1

• Mild-moderate CAP with comorbidities:

  • Amoxicillin 500 mg-1g PO q8h or amoxicillin-clavulanate 875/125 mg PO BID 1
  • PLUS a macrolide (clarithromycin) to cover atypical pathogens 1

Key considerations:

• Amoxicillin provides excellent coverage against >93% of S. pneumoniae strains 1
• Clarithromycin is preferred over erythromycin due to fewer adverse events (OR 0.30; 95% CI 0.20-0.46) 2
• Azithromycin should be used cautiously due to increased risk of cardiovascular events 2
• Standard treatment duration: 5 days if afebrile for 48-72 hours and clinically stable 1

Inpatient Treatment (Moderate-Severe CAP)

Non-ICU hospitalized patients:

• Preferred regimen:
  • IV beta-lactam (ceftriaxone, cefotaxime, or ampicillin-sulbactam) PLUS a macrolide 1

ICU patients with severe CAP:

• Preferred regimen:
  • IV beta-lactam (ceftriaxone, cefotaxime, or ampicillin-sulbactam) PLUS a macrolide 2, 1
  • For suspected Pseudomonas: piperacillin-tazobactam or carbapenem PLUS ciprofloxacin/levofloxacin OR beta-lactam with aminoglycoside and azithromycin 2
  • For suspected MRSA: Add vancomycin or linezolid 2, 1

Respiratory fluoroquinolones (levofloxacin, moxifloxacin):

• Should be reserved for specific situations:
  • When first-line therapy has failed
  • Patient allergies to alternative agents
  • Documented highly drug-resistant pneumococci (penicillin MIC ≥4 μg/mL) 1, 3
• Use judiciously to prevent emergence of resistance 1

Pathogen Coverage Considerations

Common CAP pathogens:

• Typical: Streptococcus pneumoniae, Haemophilus influenzae
• Atypical: Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella pneumophila 1, 3

Special considerations:

• Recent data suggests only 37% of patients with Legionella, Mycoplasma, or Chlamydophila pneumonia receive appropriate coverage 4
• Consider local resistance patterns when selecting therapy
• For DRSP (drug-resistant S. pneumoniae), higher doses of beta-lactams may be necessary 1

Treatment Duration

• Minimum 5 days of antibiotic therapy 1
• Patient should be afebrile for 48-72 hours before discontinuing antibiotics 1
• Standard duration: 5-7 days for most patients 1
• Clinical response should be assessed within 48-72 hours of initiating therapy 1

Caveats and Pitfalls

• Avoid fluoroquinolone overuse: Despite excellent activity against DRSP, reserve for specific situations to prevent resistance development 1
• Macrolide monotherapy limitations: Not recommended for areas with high DRSP prevalence 1
• Vancomycin: Not routinely indicated for CAP or DRSP unless MRSA is suspected 5
• Narrow vs. broad-spectrum: Recent evidence suggests ampicillin plus macrolide may be comparable to ceftriaxone plus macrolide for hospitalized CAP patients, with lower rates of C. difficile infection 6
• Piperacillin-tazobactam overuse: Despite being commonly prescribed for CAP (32% in one study), this broad-spectrum agent should be reserved for specific situations like suspected Pseudomonas 4

By following these evidence-based recommendations, clinicians can provide effective empiric therapy for CAP while practicing antimicrobial stewardship.