What is the recommended treatment guideline for community-acquired pneumonia (CAP) in adults?

Community-Acquired Pneumonia Treatment Guidelines

Outpatient Treatment (Non-Hospitalized Patients)

For healthy adults without comorbidities, amoxicillin 1 g three times daily is the preferred first-line therapy, with doxycycline 100 mg twice daily as an acceptable alternative. 1

• Macrolides (azithromycin 500 mg on day 1, then 250 mg daily; or clarithromycin 500 mg twice daily) should only be used in areas where pneumococcal macrolide resistance is <25% 1
• For patients with comorbidities (diabetes, heart disease, COPD, chronic kidney disease), combination therapy is required: β-lactam (amoxicillin/clavulanate, cefpodoxime, or cefuroxime) plus macrolide (azithromycin or clarithromycin) or doxycycline 1
• Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) is an alternative for patients with comorbidities 1, 2
• Patients with recent antibiotic exposure within the past 3 months should receive a different antibiotic class to prevent resistance 2

Inpatient Treatment (Non-ICU Hospitalized Patients)

The standard regimen for hospitalized patients is β-lactam (ceftriaxone 1-2 g IV daily, cefotaxime 1-2 g IV every 8 hours, or ampicillin-sulbactam 3 g IV every 6 hours) plus azithromycin 500 mg daily, with strong recommendation and high-quality evidence. 1

• Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg IV daily or moxifloxacin 400 mg IV daily) is equally effective as an alternative regimen 1, 3, 4
• The first antibiotic dose must be administered in the emergency department before hospital admission, as delayed administration increases 30-day mortality by 20-30% 1
• Blood and sputum cultures should be obtained before initiating antibiotics in all hospitalized patients 1
• Transition from IV to oral therapy when patients are hemodynamically stable, clinically improving, able to take oral medications, and have normal GI function, typically by day 2-3 1

ICU Treatment (Severe CAP)

For severe CAP requiring ICU admission, mandatory combination therapy consists of β-lactam (ceftriaxone 2 g IV daily, cefotaxime 1-2 g IV every 8 hours, or ampicillin-sulbactam 3 g IV every 6 hours) plus either azithromycin 500 mg daily or respiratory fluoroquinolone (levofloxacin 750 mg IV daily or moxifloxacin 400 mg IV daily). 1

• For penicillin-allergic ICU patients, use respiratory fluoroquinolone plus aztreonam 2 g IV every 8 hours 1
• For suspected Pseudomonas infection (structural lung disease, recent hospitalization with IV antibiotics, prior Pseudomonas isolation), use antipseudomonal β-lactam (piperacillin-tazobactam 4.5 g IV every 6 hours, cefepime 2 g IV every 8 hours, imipenem 500 mg IV every 6 hours, or meropenem 1 g IV every 8 hours) plus ciprofloxacin 400 mg IV every 8 hours or levofloxacin 750 mg IV daily, plus aminoglycoside (gentamicin 5-7 mg/kg IV daily or tobramycin 5-7 mg/kg IV daily) 1
• For suspected MRSA (post-influenza pneumonia, cavitary infiltrates, prior MRSA infection, recent hospitalization with IV antibiotics), add vancomycin 15 mg/kg IV every 8-12 hours (target trough 15-20 mg/mL) or linezolid 600 mg IV every 12 hours 1

Duration of Therapy

Treat for a minimum of 5-7 days for uncomplicated CAP once clinical stability is achieved (afebrile for 48-72 hours with no more than one sign of clinical instability). 1

• Extend treatment to 14-21 days for Legionella, Staphylococcus aureus, or Gram-negative enteric bacilli pneumonia 5, 1
• Levofloxacin 750 mg daily for 5 days is as effective as 500 mg daily for 10 days for mild to severe CAP 3

Failure to Improve

If no clinical improvement by day 2-3, conduct a careful review of clinical history, examination, prescription chart, and all investigation results. 5

• Obtain repeat chest radiograph, CRP, white cell count, and additional microbiological specimens 5
• For non-severe pneumonia on amoxicillin monotherapy, substitute or add a macrolide 5
• For non-severe pneumonia on combination therapy, consider switching to a respiratory fluoroquinolone 5
• For severe pneumonia not responding to combination therapy, consider adding rifampicin 5

Critical Pitfalls to Avoid

• Never use macrolide monotherapy in areas with >25% pneumococcal macrolide resistance 1
• Avoid cefuroxime, cefepime, piperacillin-tazobactam, or carbapenems as first-line empiric therapy unless specific risk factors for Pseudomonas or MRSA are present 1
• Do not automatically escalate to broad-spectrum antibiotics based solely on immunosuppression without documented risk factors 1
• Never delay antibiotic administration beyond 8 hours in hospitalized patients 1
• Avoid extending therapy beyond 7 days in responding patients without specific indications, as this increases resistance risk 1