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

Initial Treatment for Community-Acquired Pneumonia (CAP)

The initial empiric antibiotic therapy for community-acquired pneumonia should be based on the patient's risk factors, severity of illness, and treatment setting, with a combination of a β-lactam plus a macrolide being the recommended regimen for hospitalized non-ICU patients. 1

Outpatient Treatment (Non-Severe CAP)

• For previously healthy outpatients with no risk factors for drug-resistant pathogens, a macrolide (such as azithromycin) is recommended as first-line therapy 1
• Azithromycin dosing for adults with CAP: 500 mg as a single dose on Day 1, followed by 250 mg once daily on Days 2 through 5 2
• Doxycycline 100 mg twice daily is an alternative first-line option for outpatients without comorbidities 1
• For outpatients with comorbidities or recent antibiotic use, a respiratory fluoroquinolone or a β-lactam plus a macrolide is recommended 1, 3
• Most outpatients can be adequately treated with oral antibiotics 4

Hospitalized Non-ICU Patients

• Combined oral therapy with amoxicillin and a macrolide (erythromycin or clarithromycin) is preferred for patients who require hospital admission for clinical reasons 4
• When oral treatment is contraindicated, recommended parenteral choices include intravenous ampicillin or benzylpenicillin, together with erythromycin or clarithromycin 4
• A respiratory fluoroquinolone alone (levofloxacin or moxifloxacin) can be used as an alternative treatment option 1
• For hospitalized patients, the first antibiotic dose should be administered while still in the emergency department, with early administration associated with improved outcomes 1

Severe CAP/ICU Treatment

• Patients with severe pneumonia should be treated immediately after diagnosis with parenteral antibiotics 4
• An intravenous combination of a broad spectrum β-lactamase stable antibiotic such as co-amoxiclav or a second generation (e.g., cefuroxime) or third generation (e.g., cefotaxime or ceftriaxone) cephalosporin together with a macrolide (e.g., clarithromycin or erythromycin) is preferred 4
• For patients with risk factors for Pseudomonas, an antipseudomonal β-lactam plus either ciprofloxacin or levofloxacin, an aminoglycoside plus azithromycin, or an aminoglycoside plus an antipneumococcal fluoroquinolone is recommended 1

Duration of Therapy

• Patients with CAP should be treated for a minimum of 5 days 4
• Patients should be afebrile for 48–72 hours and have no more than one CAP-associated sign of clinical instability before discontinuation of therapy 4, 1
• For patients with severe microbiologically undefined pneumonia, 10 days of treatment is proposed 4
• Treatment should be extended to 14–21 days where legionella, staphylococcal, or Gram negative enteric bacilli pneumonia are suspected or confirmed 4

Special Considerations

• Once the etiology of CAP has been identified on the basis of reliable microbiological methods, antimicrobial therapy should be directed at that pathogen 4, 1
• For patients who fail to improve as expected, there should be a careful review of the clinical history, examination, prescription chart, and results of all available investigation results 4
• Add vancomycin or linezolid when community-acquired MRSA is suspected, with risk factors including prior MRSA infection, recent hospitalization, or recent antibiotic use 1
• Patients initially treated with parenteral antibiotics should be transferred to an oral regimen as soon as clinical improvement occurs and temperature has been normal for 24 hours 1

Common Pitfalls and Caveats

• Overreliance on fluoroquinolones can lead to resistance, and they should be reserved for patients with β-lactam allergies or when specifically indicated 1
• Inadequate coverage for atypical pathogens should be avoided, ensuring coverage for Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila 1
• Recent studies show increasing multidrug resistance in bacteria causing CAP, particularly concerning for S. pneumoniae, K. pneumoniae, and P. aeruginosa 5
• Delaying antibiotic administration is associated with increased mortality, particularly in severe pneumonia 1, 6
• Failure to adjust therapy based on culture results can lead to unnecessary prolonged therapy 1