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

Initial Treatment for Community-Acquired Pneumonia in Adults

The recommended initial empiric antibiotic therapy for community-acquired pneumonia (CAP) in adults 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, 2

Outpatient Treatment

• For previously healthy outpatients with no risk factors for drug-resistant pathogens, a macrolide (such as azithromycin) is recommended as first-line therapy 1, 2, 3
• Amoxicillin 1g every 8 hours is an alternative first-line therapy for outpatients without comorbidities 2, 3
• Doxycycline 100mg twice daily is another alternative first-line option for outpatients without comorbidities 2, 3
• For outpatients with comorbidities or recent antibiotic use, a respiratory fluoroquinolone or a β-lactam plus a macrolide is recommended 1, 2
• Most outpatients can be adequately treated with oral antibiotics 4, 2

Hospitalized Non-ICU Patients

• Combined therapy with amoxicillin and a macrolide (erythromycin or clarithromycin) is preferred for patients who require hospital admission for clinical reasons 4, 2
• A β-lactam (such as ceftriaxone) plus a macrolide (such as clarithromycin) is the preferred regimen for hospitalized non-ICU patients 1, 2
• A respiratory fluoroquinolone alone (levofloxacin or moxifloxacin) can be used as an alternative treatment option 1, 2
• When oral treatment is contraindicated, recommended parenteral choices include intravenous ampicillin or benzylpenicillin, together with erythromycin or clarithromycin 4, 2

Severe CAP/ICU Treatment

• Patients with severe pneumonia should be treated immediately after diagnosis with parenteral antibiotics 4, 2
• An intravenous combination of a broad-spectrum β-lactamase stable antibiotic (co-amoxiclav, cefuroxime, cefotaxime, or ceftriaxone) together with a macrolide (clarithromycin or erythromycin) is preferred 4, 2, 3
• 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, 3

Duration of Therapy

• The minimum duration of therapy is 5 days for most patients, with the patient required to be afebrile for 48-72 hours and have no more than one sign of clinical instability before discontinuing therapy 1, 2
• For patients with severe microbiologically undefined pneumonia, 10 days of treatment is proposed 4, 3
• Treatment should be extended to 14-21 days where legionella, staphylococcal, or Gram-negative enteric bacilli pneumonia are suspected or confirmed 4, 2

Special Considerations

• For hospitalized patients, the first antibiotic dose should be administered while still in the emergency department, with early administration associated with improved outcomes 1
• Add vancomycin or linezolid when community-acquired MRSA is suspected, with risk factors including prior MRSA infection, recent hospitalization, or recent antibiotic use 1, 2
• 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 2
• Once the etiology of CAP has been identified, antimicrobial therapy should be directed at that pathogen 2

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, 2, 3
• Inadequate coverage for atypical pathogens should be avoided, ensuring coverage for Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila 1, 3
• Delaying antibiotic administration is associated with increased mortality, particularly in severe pneumonia 2
• 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, 3
• When a change in empirical antibiotic treatment is considered necessary, a macrolide could be substituted for or added to the treatment for those with non-severe pneumonia treated with amoxicillin monotherapy 4, 3

Evidence Strength and Considerations

• Recent guidelines from the Infectious Diseases Society of America and the American Thoracic Society provide strong recommendations for the use of combination therapy with a β-lactam plus a macrolide for hospitalized patients 1, 2
• Clinical trials have shown that fluoroquinolone monotherapy is as efficacious as β-lactam-macrolide combination therapy in the treatment of CAP patients 5
• Recent studies suggest that a subset of patients may not require atypical coverage as part of their regimen, but this remains controversial 6
• The most recent comprehensive review in JAMA confirms that hospitalized patients without risk factors for resistant bacteria can be treated with β-lactam/macrolide combination therapy, such as ceftriaxone combined with azithromycin 7