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

Recommended Antibiotic Regimens for Community-Acquired Pneumonia (CAP)

For community-acquired pneumonia, the recommended antibiotic regimens vary based on patient setting, comorbidities, and risk factors, with combination therapy of a β-lactam plus macrolide or respiratory fluoroquinolone monotherapy being strongly recommended for hospitalized patients. 1, 2

Outpatient Treatment

Healthy Adults Without Comorbidities

• Macrolide (azithromycin 500 mg on day 1, then 250 mg daily for days 2-5, or clarithromycin 500 mg twice daily) 1, 3
• Doxycycline 100 mg twice daily as an alternative option 1, 2
• Note: Macrolides should only be used in areas where pneumococcal resistance to macrolides is <25% 2

Adults With Comorbidities or Risk Factors for DRSP

• Respiratory fluoroquinolone (moxifloxacin, gemifloxacin, or levofloxacin 750 mg) 1, 4
• β-lactam plus a macrolide (high-dose amoxicillin 1g three times daily or amoxicillin-clavulanate 2g twice daily preferred; alternatives include ceftriaxone, cefpodoxime, and cefuroxime) 1, 2
• If patient has received antibiotics within the previous 3 months, select an agent from a different class 1, 2

Inpatient Treatment (Non-ICU)

• β-lactam (ampicillin + sulbactam 1.5-3g every 6h, cefotaxime 1-2g every 8h, ceftriaxone 1-2g daily, or ceftaroline 600mg every 12h) plus a macrolide (azithromycin 500mg daily or clarithromycin 500mg twice daily) 1, 2
• Respiratory fluoroquinolone monotherapy (levofloxacin 750mg daily or moxifloxacin 400mg daily) 1, 2
• For penicillin-allergic patients: respiratory fluoroquinolone 1, 2
• Alternative option: β-lactam plus doxycycline 100mg twice daily 1

Inpatient Treatment (ICU)

• β-lactam (cefotaxime, ceftriaxone, or ampicillin-sulbactam) plus either azithromycin or a respiratory fluoroquinolone 1, 2
• For penicillin-allergic patients: respiratory fluoroquinolone plus aztreonam 1, 2

Special Considerations

Pseudomonas Risk

• Antipseudomonal β-lactam (piperacillin-tazobactam, cefepime, imipenem, or meropenem) plus either ciprofloxacin/levofloxacin or an aminoglycoside and azithromycin 1, 2

MRSA Risk

• Add vancomycin or linezolid to the standard regimen 1, 2

Duration of Therapy

• Standard duration of 5-7 days for most uncomplicated CAP 2, 5
• Shorter durations (3 days) may be effective for some patients, even when hospitalized 5
• Longer courses may be needed for more severe infections or specific pathogens 2

Clinical Considerations and Potential Pitfalls

• Administer the first antibiotic dose while still in the emergency department for hospitalized patients to reduce mortality risk 2
• Switch from IV to oral therapy when patients are hemodynamically stable, clinically improving, able to take oral medications, and have normal GI function 2
• Avoid macrolide monotherapy in areas with high resistance rates (>25%) to prevent treatment failure 1, 2
• Recent antibiotic exposure increases risk of resistant organisms and should guide therapy selection 1, 2
• The addition of a macrolide to a β-lactam has been associated with decreased mortality and reduced length of stay in observational studies 6, 7
• Adjust therapy when culture results become available to ensure appropriate coverage 2, 4

Regional Variations in Guidelines

• North American guidelines (IDSA/ATS) favor macrolides and doxycycline for outpatient treatment 1
• British and European guidelines traditionally recommend amoxicillin as first-line therapy for outpatient CAP, with macrolides reserved for penicillin-allergic patients 1
• This difference reflects varying approaches to balancing coverage of atypical pathogens against concerns about antibiotic resistance 1, 8