What are the recommended antibiotic regimens for community-acquired pneumonia (CAP) in adults?

Antibiotic Regimen Recommendations for Community-Acquired Pneumonia in Adults

For community-acquired pneumonia (CAP) in adults, the recommended antibiotic regimens should be stratified based on treatment setting, severity of illness, and patient risk factors to ensure optimal outcomes for morbidity and mortality.

Outpatient Treatment

Healthy Adults Without Comorbidities

• Amoxicillin 1 g three times daily is the preferred first-line therapy due to its effectiveness against common CAP pathogens and moderate quality evidence supporting its use 1
• Doxycycline 100 mg twice daily is an acceptable alternative (conditional recommendation) 1
• Macrolides (azithromycin 500 mg on first day then 250 mg daily, or clarithromycin 500 mg twice daily) should only be used in areas where pneumococcal resistance to macrolides is <25% 1

Adults With Comorbidities

Comorbidities include: chronic heart, lung, liver, or renal disease; diabetes mellitus; alcoholism; malignancy; asplenia; or recent antibiotic use within 3 months 1

Recommended options (no particular order of preference):

• Combination therapy:

  • β-lactam (amoxicillin/clavulanate 500/125 mg three times daily, 875/125 mg twice daily, or 2000/125 mg twice daily, OR cefpodoxime 200 mg twice daily, OR cefuroxime 500 mg twice daily) PLUS
  • Macrolide (azithromycin or clarithromycin) or doxycycline 1

• Monotherapy:

  • Respiratory fluoroquinolone (levofloxacin 750 mg daily, moxifloxacin 400 mg daily, or gemifloxacin 320 mg daily) 1, 2

Inpatient Treatment (Non-ICU)

• β-lactam (ampicillin + sulbactam, cefotaxime, ceftriaxone, or ceftaroline) plus a macrolide (strong recommendation, high quality evidence) 1
• Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) (strong recommendation, high quality evidence) 1
• For penicillin-allergic patients, use a respiratory fluoroquinolone 1
• Alternative: β-lactam plus doxycycline (conditional recommendation, low quality evidence) 1

Inpatient Treatment (ICU)

• β-lactam (cefotaxime, ceftriaxone, or ampicillin-sulbactam) plus either azithromycin or a respiratory fluoroquinolone (strong recommendation) 1
• For penicillin-allergic patients, use a respiratory fluoroquinolone plus aztreonam 1

Special Considerations for ICU Patients

• For suspected Pseudomonas infection: Antipseudomonal β-lactam (piperacillin-tazobactam, cefepime, imipenem, or meropenem) plus either ciprofloxacin/levofloxacin OR an aminoglycoside plus azithromycin OR an aminoglycoside plus an antipneumococcal fluoroquinolone 1
• For suspected community-acquired MRSA: Add vancomycin or linezolid to the regimen 1, 3

Duration of Therapy

• Standard duration for most patients is 5-7 days for uncomplicated CAP 1
• For more severe infections or specific pathogens, longer courses may be needed 1

Key Clinical Considerations

• Administer first antibiotic dose while still in the emergency department for hospitalized patients 1
• Switch from IV to oral therapy when patients are hemodynamically stable, clinically improving, able to take oral medications, and have normal GI function 1
• In areas with high rates (>25%) of macrolide-resistant S. pneumoniae, avoid macrolide monotherapy 1
• Recent studies show doxycycline may be a cost-effective alternative to levofloxacin with similar efficacy in non-severe CAP 4
• Fluoroquinolones are associated with higher rates of adverse events compared to macrolides but may have lower retreatment rates 5
• The combination of a third-generation cephalosporin and a macrolide has shown excellent efficacy against S. pneumoniae, including resistant strains 6

Pitfalls to Avoid

• Using macrolide monotherapy in areas with high resistance rates can lead to treatment failure 1, 7
• Delaying antibiotic administration in hospitalized patients increases mortality risk 1
• Failing to consider patient-specific factors such as recent antibiotic exposure, which may increase risk of resistant organisms 1
• Not adjusting therapy when culture results become available 1
• Overlooking the potential for Pseudomonas or MRSA in patients with specific risk factors 1

The most recent guidelines emphasize the importance of early, appropriate antibiotic therapy based on local resistance patterns and patient risk factors to reduce morbidity and mortality in community-acquired pneumonia 1.