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

Treatment for Community-Acquired Pneumonia (CAP)

For outpatient CAP in previously healthy adults, amoxicillin 1g three times daily is the preferred first-line therapy, with doxycycline 100mg twice daily as an acceptable alternative. 1

Outpatient Treatment

Previously Healthy Adults (No Comorbidities)

First-line therapy:

• Amoxicillin 1g orally three times daily is the preferred agent based on moderate quality evidence supporting effectiveness against common CAP pathogens 1, 2
• Doxycycline 100mg orally twice daily serves as an acceptable alternative, though with lower quality evidence 1, 2

Macrolide considerations:

• Azithromycin (500mg day 1, then 250mg daily) or clarithromycin (500mg twice daily) should only be used when local pneumococcal macrolide resistance is documented <25% 1, 2
• In areas with resistance >25%, macrolide monotherapy leads to treatment failure and should be avoided 1

Adults with Comorbidities (COPD, diabetes, renal/heart failure, malignancy)

Two equally effective options:

1. Combination therapy: β-lactam (amoxicillin-clavulanate 2g twice daily, cefpodoxime, or cefuroxime) PLUS macrolide (azithromycin or clarithromycin) OR doxycycline 1, 2

2. Respiratory fluoroquinolone monotherapy: Levofloxacin 750mg daily, moxifloxacin 400mg daily, or gemifloxacin 320mg daily 1, 2

Critical caveat: Avoid indiscriminate fluoroquinolone use in uncomplicated cases due to FDA warnings about serious adverse events and resistance concerns 1

Inpatient Non-ICU Treatment

Two regimens with strong recommendations and high-quality evidence:

1. β-lactam plus macrolide combination (preferred):

   • Ceftriaxone 1-2g IV daily PLUS azithromycin 500mg daily 1, 2, 3
   • Alternative β-lactams: cefotaxime 1-2g IV every 8 hours or ampicillin-sulbactam 3g IV every 6 hours 1

2. Respiratory fluoroquinolone monotherapy:

   • Levofloxacin 750mg IV daily OR moxifloxacin 400mg IV daily 1, 2
   • Systematic reviews show fewer clinical failures with fluoroquinolones compared to β-lactam/macrolide combinations 1

For penicillin-allergic patients: Use respiratory fluoroquinolone as the preferred alternative 1, 2

Critical timing: Administer the first antibiotic dose in the emergency department—delayed administration beyond 8 hours increases 30-day mortality by 20-30% 1, 3

ICU/Severe CAP Treatment

Mandatory combination therapy for all ICU patients:

Standard regimen (no Pseudomonas risk):

• 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, 3

For Pseudomonas aeruginosa 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 or levofloxacin PLUS aminoglycoside (gentamicin 5-7mg/kg IV daily or tobramycin 5-7mg/kg IV daily) PLUS azithromycin 1, 2

For MRSA risk factors (prior MRSA infection/colonization, recent hospitalization with IV antibiotics, post-influenza pneumonia, cavitary infiltrates):

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

For penicillin-allergic ICU patients:

• Respiratory fluoroquinolone PLUS aztreonam 2g IV every 8 hours 1

Duration of Therapy

Standard duration:

• Minimum 5 days and until afebrile for 48-72 hours with no more than one sign of clinical instability 4, 1, 2, 3
• Typical duration for uncomplicated CAP: 5-7 days 1, 2

Extended duration (14-21 days) required for:

• Legionella pneumophila 1, 2
• Staphylococcus aureus 1, 2
• Gram-negative enteric bacilli 1, 2

Critical pitfall: Avoid extending therapy beyond 7 days in responding patients without specific indications, as this increases antimicrobial resistance risk 1

Transition from IV to Oral Therapy

Switch criteria (all must be met):

• Hemodynamically stable 4, 1, 2
• Clinically improving 4, 1, 2
• Able to ingest medications 4, 1, 2
• Normally functioning gastrointestinal tract 4, 1, 2
• Typically achieved by day 2-3 of hospitalization 1, 2

Recommended oral step-down regimens:

• Amoxicillin 1g orally three times daily PLUS azithromycin 500mg orally daily 1
• Alternative macrolide: clarithromycin 500mg orally twice daily 1

Discharge criteria: Patients should be discharged as soon as clinically stable with no other active medical problems and a safe environment for continued care—inpatient observation while receiving oral therapy is unnecessary 4

Special Considerations

Obtain blood and sputum cultures before initiating antibiotics in all hospitalized patients to allow pathogen-directed therapy 1, 2

Avoid these common errors:

• Never use macrolide monotherapy in hospitalized patients—provides inadequate coverage for typical bacterial pathogens like S. pneumoniae 1
• Never use cefuroxime, cefepime, piperacillin-tazobactam, or carbapenems as first-line empiric therapy unless specific risk factors for Pseudomonas or MRSA are present 1
• Never delay antibiotic administration beyond 8 hours in hospitalized patients 1, 3

For patients with recent antibiotic exposure: Select an alternative regimen from a different antibiotic class to minimize resistance risk 1, 2

Systemic corticosteroids: Consider administration within 24 hours of severe CAP development, as this may reduce 28-day mortality 3

Follow-Up

Clinical review at 6 weeks for all hospitalized patients 1, 2

Chest radiograph at 6 weeks reserved for patients with:

• Persistent symptoms 1, 2
• Physical signs 1, 2
• High risk for underlying malignancy (smokers, age >50 years) 1, 2

Chest radiograph not required before hospital discharge in patients with satisfactory clinical recovery 1, 2