What are the initial treatment recommendations for Community-Acquired Pneumonia (CAP)?

Community-Acquired Pneumonia Treatment Recommendations

For hospitalized non-ICU patients with CAP, use combination therapy with a β-lactam (ceftriaxone 1-2g IV daily) plus azithromycin (500mg daily), or alternatively, respiratory fluoroquinolone monotherapy (levofloxacin 750mg daily or moxifloxacin 400mg daily). 1, 2

Treatment Algorithm by Clinical Setting

Outpatient Treatment (Previously Healthy, No Comorbidities)

• Amoxicillin 1g three times daily is the preferred first-line therapy for healthy adults without comorbidities, based on strong recommendation and moderate quality evidence 1, 2
• Doxycycline 100mg twice daily serves as an acceptable alternative (conditional recommendation, low quality evidence) 1, 2
• Avoid macrolide monotherapy (azithromycin or clarithromycin) unless local pneumococcal macrolide resistance is documented to be <25%, as resistance rates commonly range 30-40% and often co-exist with β-lactam resistance 1, 2

Outpatient Treatment (With Comorbidities or Recent Antibiotic Use)

• Use combination therapy with a β-lactam (amoxicillin-clavulanate, cefpodoxime, or cefuroxime) plus either a macrolide (azithromycin or clarithromycin) or doxycycline 1, 2
• Alternatively, use respiratory fluoroquinolone monotherapy (levofloxacin 750mg daily, moxifloxacin 400mg daily, or gemifloxacin) 1, 2
• Patients with recent exposure to one antibiotic class should receive treatment from a different class due to increased bacterial resistance risk 1

Hospitalized Non-ICU Patients

• The standard regimen is ceftriaxone 1-2g IV daily plus azithromycin 500mg daily (strong recommendation, high quality evidence) 1, 2, 3
• Respiratory fluoroquinolone monotherapy (levofloxacin 750mg IV daily or moxifloxacin 400mg IV daily) is equally effective as an alternative (strong recommendation, high quality evidence) 1, 2
• β-lactam plus doxycycline can be used as an alternative but carries lower quality evidence (conditional recommendation) 1, 2
• Administer the first antibiotic dose while still in the emergency department, as delayed administration beyond 8 hours increases 30-day mortality by 20-30% 1, 2

Severe CAP Requiring ICU Admission

• Mandatory combination therapy with β-lactam (ceftriaxone 2g IV daily, cefotaxime 1-2g IV every 8 hours, or ampicillin-sulbactam 3g IV every 6 hours) plus either azithromycin 500mg daily or respiratory fluoroquinolone (levofloxacin 750mg IV daily or moxifloxacin 400mg IV daily) 1, 2
• This provides coverage against both typical and atypical pathogens with strong recommendation and level II evidence 1, 2

Special Considerations for Resistant Pathogens

Pseudomonas aeruginosa Risk Factors

• Add antipseudomonal coverage if the patient has: structural lung disease, recent hospitalization with IV antibiotics within 90 days, or prior respiratory isolation of P. aeruginosa 1, 2
• Use antipseudomonal β-lactam (piperacillin-tazobactam, cefepime, imipenem, or meropenem) plus either ciprofloxacin 400mg IV every 8 hours or levofloxacin 750mg IV daily 1, 2
• Alternative: antipseudomonal β-lactam plus aminoglycoside (gentamicin 5-7mg/kg IV daily or tobramycin 5-7mg/kg IV daily) plus azithromycin 1, 2

MRSA Risk Factors

• Add vancomycin 15mg/kg IV every 8-12 hours (target trough 15-20 mg/mL) or linezolid 600mg IV every 12 hours when MRSA is suspected 1, 2
• Risk factors include: post-influenza pneumonia, cavitary infiltrates on imaging, prior MRSA infection/colonization, or recent hospitalization with IV antibiotics 1, 2

Duration of Therapy

• Treat for a minimum of 5 days and until the patient is afebrile for 48-72 hours with no more than one sign of clinical instability 1, 2
• Standard duration is 5-7 days for uncomplicated CAP once clinical stability is achieved 1, 2
• Extend duration to 14-21 days for Legionella pneumophila, Staphylococcus aureus, or Gram-negative enteric bacilli 1, 2
• Treatment should generally not exceed 8 days in a responding patient without specific indications 1

Transition to Oral Therapy

• Switch from IV to oral therapy when the patient is hemodynamically stable, clinically improving, able to ingest medications, and has normal GI function—typically by day 2-3 of hospitalization 1, 2
• Oral step-down options include: amoxicillin 1g three times daily plus azithromycin 500mg daily, or respiratory fluoroquinolone monotherapy 1, 2

Penicillin-Allergic Patients

• For non-ICU hospitalized patients: use respiratory fluoroquinolone monotherapy (levofloxacin 750mg IV daily or moxifloxacin 400mg IV daily) 1, 2
• For ICU patients: use respiratory fluoroquinolone plus aztreonam 2g IV every 8 hours 2

Critical Pitfalls to Avoid

• Do not use macrolide monotherapy for hospitalized patients, as this provides inadequate coverage for typical bacterial pathogens like S. pneumoniae 1, 2
• Reserve fluoroquinolones for patients with β-lactam allergies or specific indications to prevent resistance development 1
• Do not automatically escalate to broad-spectrum antibiotics based solely on comorbidities without documented risk factors for resistant organisms 2
• Avoid extending therapy beyond 7 days in responding patients without specific indications, as this increases antimicrobial resistance risk 1, 2
• Do not use cefuroxime, cefepime, piperacillin-tazobactam, or carbapenems as first-line empiric therapy unless specific risk factors for Pseudomonas or MRSA are present 2

Diagnostic Testing

• Obtain blood cultures and sputum cultures before initiating antibiotics in all hospitalized patients to allow pathogen-directed therapy 1, 2
• Test all patients for COVID-19 and influenza when these viruses are common in the community 3
• Chest radiograph is not required before hospital discharge in patients with satisfactory clinical recovery 1
• Schedule clinical review at 6 weeks for all hospitalized patients, with chest radiograph reserved for those with persistent symptoms or high risk for underlying malignancy (smokers, age >50 years) 1