What is the recommended treatment for a patient with community-acquired pneumonia (CAP)?

Community-Acquired Pneumonia Treatment

For outpatients without comorbidities, use amoxicillin 1g three times daily for 5-7 days; for hospitalized non-ICU patients, use ceftriaxone 1-2g IV daily plus azithromycin 500mg daily; for ICU patients, mandatory combination therapy with ceftriaxone 2g IV daily plus azithromycin 500mg IV daily or a respiratory fluoroquinolone is required. 1

Outpatient Treatment Algorithm

Previously Healthy Adults Without Comorbidities

• First-line: Amoxicillin 1g orally three times daily for 5-7 days provides optimal coverage against Streptococcus pneumoniae including drug-resistant strains 1, 2
• Alternative: Doxycycline 100mg orally twice daily if amoxicillin is not tolerated 1, 2
• Macrolides (azithromycin 500mg day 1, then 250mg daily for days 2-5) should ONLY be used when local pneumococcal macrolide resistance is documented <25% 1, 3

Adults With Comorbidities (COPD, diabetes, heart/liver/renal disease, malignancy)

• Combination therapy: Amoxicillin-clavulanate 875mg/125mg twice daily PLUS azithromycin 500mg day 1, then 250mg daily for 5-7 days total 1, 2
• Alternative monotherapy: Respiratory fluoroquinolone (levofloxacin 750mg daily OR moxifloxacin 400mg daily) for 5-7 days 1, 4

Critical pitfall: Never use macrolide monotherapy in patients with comorbidities—this provides inadequate coverage for typical bacterial pathogens and leads to treatment failure 1

Inpatient Non-ICU Treatment

Standard Regimen (Two Equally Effective Options)

• β-lactam plus macrolide: Ceftriaxone 1-2g IV daily PLUS azithromycin 500mg daily (strong recommendation, high-quality evidence) 1, 5, 6
• Fluoroquinolone monotherapy: Levofloxacin 750mg IV daily OR moxifloxacin 400mg IV daily 1, 4

Transition to Oral Therapy

• Switch when patient is hemodynamically stable, clinically improving, afebrile for 48-72 hours, able to take oral medications, and has normal GI function—typically by day 2-3 1, 2
• Oral step-down: Amoxicillin 1g three times daily PLUS azithromycin 500mg daily to complete 5-7 days total 1

Penicillin-Allergic Patients

• Respiratory fluoroquinolone (levofloxacin 750mg IV daily OR moxifloxacin 400mg IV daily) is the preferred alternative 1, 2

Critical timing: Administer the first antibiotic dose immediately in the emergency department—delayed administration beyond 8 hours increases 30-day mortality by 20-30% 1, 5

ICU/Severe CAP Treatment

Mandatory Combination Therapy

Monotherapy is NEVER adequate for severe CAP 1, 2

• Standard regimen: Ceftriaxone 2g IV daily PLUS azithromycin 500mg IV daily 1, 5
• Alternative: Ceftriaxone 2g IV daily PLUS levofloxacin 750mg IV daily OR moxifloxacin 400mg IV daily 1, 2

Special Populations Requiring Broader Coverage

Pseudomonas Risk Factors (structural lung disease, recent hospitalization with IV antibiotics within 90 days, prior P. aeruginosa isolation):

• Antipseudomonal β-lactam (piperacillin-tazobactam, cefepime, imipenem, or meropenem) PLUS ciprofloxacin 400mg IV every 8 hours OR levofloxacin 750mg IV daily PLUS aminoglycoside (gentamicin 5-7mg/kg IV daily) 1, 2

MRSA Risk Factors (prior MRSA infection, recent hospitalization with IV antibiotics, post-influenza pneumonia, cavitary infiltrates):

• ADD vancomycin 15mg/kg IV every 8-12 hours (target trough 15-20 mg/mL) OR linezolid 600mg IV every 12 hours to base regimen 1, 2

Duration of Therapy

• Uncomplicated CAP: Minimum 5 days and until afebrile for 48-72 hours with no more than one sign of clinical instability; typical duration 5-7 days 1, 2, 5
• Extended duration (14-21 days): Required for Legionella pneumophila, Staphylococcus aureus, or Gram-negative enteric bacilli 1, 2

Do NOT extend therapy beyond 7 days in responding patients without specific indications—this increases antimicrobial resistance risk without improving outcomes 1

Treatment Failure Management

If no clinical improvement by day 2-3:

• Obtain repeat chest radiograph, CRP, white cell count, and additional microbiological specimens 1, 2
• Consider chest CT to reveal unsuspected pleural effusions, lung abscess, or central airway obstruction 1
• For non-severe pneumonia on amoxicillin monotherapy: ADD or substitute a macrolide 1
• For severe pneumonia not responding to combination therapy: Consider adding rifampicin 1

Critical Pitfalls to Avoid

1. Never use macrolide monotherapy in hospitalized patients—provides inadequate coverage for S. pneumoniae 1, 3
2. Never use macrolides when local resistance exceeds 25%—leads to treatment failure 1, 3
3. Never delay antibiotics beyond 8 hours in hospitalized patients—increases mortality by 20-30% 1, 5
4. Never use fluoroquinolones indiscriminately in uncomplicated outpatient CAP—reserve for specific indications due to resistance concerns and serious adverse events including QT prolongation, tendon rupture, and CNS effects 1, 4, 3
5. Never add antipseudomonal or MRSA coverage without documented risk factors—promotes resistance 1, 2

Follow-Up

• Clinical review at 48 hours or sooner if clinically indicated for outpatients 1, 2
• Clinical review at 6 weeks for all hospitalized patients, with chest radiograph reserved for those with persistent symptoms, physical signs, or high risk for underlying malignancy (smokers, age >50 years) 1, 2