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

Community-Acquired Pneumonia Treatment

For outpatient CAP without comorbidities, use amoxicillin 1g three times daily, doxycycline 100mg twice daily, or a macrolide (if local pneumococcal resistance is <25%). 1

Outpatient Treatment Algorithm

Patients WITHOUT Comorbidities or Risk Factors

• First-line options: 1
  • Amoxicillin 1g three times daily
  • Doxycycline 100mg twice daily
  • Macrolide (azithromycin 500mg day 1, then 250mg daily; OR clarithromycin 500mg twice daily) only if local pneumococcal resistance <25% 1

Patients WITH Comorbidities*

Choose one of these regimens: 1

• Combination therapy:

  • High-dose amoxicillin (1g three times daily) OR amoxicillin-clavulanate (2g twice daily) PLUS a macrolide 1
  • Alternative β-lactams: ceftriaxone, cefpodoxime 200mg twice daily, or cefuroxime 500mg twice daily PLUS macrolide 1
  • Doxycycline 100mg twice daily can substitute for the macrolide 1

• Monotherapy alternative:

  • Respiratory fluoroquinolone: levofloxacin 750mg daily, moxifloxacin 400mg daily, or gemifloxacin 320mg daily 1

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

Critical caveat: If antibiotics were used in the previous 3 months, select an agent from a different class to avoid resistance 1

Inpatient Non-ICU Treatment

Two equally effective options: 1

1. β-lactam PLUS macrolide (strong recommendation, high-quality evidence):

   • Ceftriaxone 1-2g daily OR cefotaxime 1-2g every 8 hours OR ampicillin-sulbactam 1.5-3g every 6 hours OR ceftaroline 600mg every 12 hours 1
   • PLUS azithromycin 500mg daily OR clarithromycin 500mg twice daily 1
   • Doxycycline 100mg twice daily is an alternative to macrolide (conditional recommendation, lower evidence) 1

2. Respiratory fluoroquinolone monotherapy (strong recommendation, high-quality evidence):

   • Levofloxacin 750mg daily OR moxifloxacin 400mg daily 1

Evidence note: Both regimens show similar mortality outcomes, though fluoroquinolone monotherapy had fewer treatment discontinuations and less diarrhea in systematic reviews 1. Recent research supports doxycycline as cost-effective with comparable efficacy to levofloxacin 2, 3.

Inpatient ICU Treatment (Severe CAP)

For severe CAP without MRSA/Pseudomonas risk factors: 1

• β-lactam (cefotaxime, ceftriaxone, or ampicillin-sulbactam) PLUS azithromycin (strong recommendation, moderate evidence) 1
• OR β-lactam PLUS respiratory fluoroquinolone (strong recommendation, level I evidence) 1

For Pseudomonas risk factors: 1

• Antipseudomonal β-lactam (piperacillin-tazobactam, cefepime, imipenem, or meropenem) 1
• PLUS ciprofloxacin OR levofloxacin 750mg 1
• OR antipseudomonal β-lactam PLUS aminoglycoside PLUS azithromycin 1

For MRSA risk factors: 1

• Add vancomycin OR linezolid to above regimens 1

Evidence note: Meta-analysis of nearly 10,000 critically ill CAP patients showed macrolide-containing regimens reduced mortality by 18% relative risk (3% absolute risk reduction) compared to non-macrolide regimens 1. Systemic corticosteroids within 24 hours may reduce 28-day mortality in severe CAP 4.

Treatment Duration & Monitoring

• Minimum 5 days of therapy (level I evidence) 1
• Patient must be afebrile for 48-72 hours 1
• No more than 1 sign of clinical instability before discontinuation 1
• Switch from IV to oral when hemodynamically stable, clinically improving, and able to tolerate oral medications (typically within first 3 days) 1, 4

Special Considerations

High macrolide resistance regions (≥25%): Use alternative agents (fluoroquinolone or β-lactam/macrolide combination) even in patients without comorbidities 1

Penicillin allergy: Use respiratory fluoroquinolone for inpatients; fluoroquinolone plus aztreonam for ICU patients 1

First antibiotic dose timing: Administer while still in emergency department for admitted patients 1