What is the initial treatment for pneumonia?

Initial Treatment for Pneumonia

For previously healthy outpatients with community-acquired pneumonia, start with amoxicillin 1g every 8 hours or a macrolide (azithromycin preferred); for hospitalized non-ICU patients, use a β-lactam (ceftriaxone) plus a macrolide (azithromycin); and for ICU patients without Pseudomonas risk, use a β-lactam plus either a macrolide or respiratory fluoroquinolone. 1, 2

Outpatient Treatment Algorithm

Previously Healthy Patients (No Comorbidities)

• First-line therapy: Amoxicillin 1g every 8 hours is the preferred initial treatment 2
• Alternative first-line: Azithromycin or doxycycline 100mg twice daily (first dose 200mg for rapid serum levels) 3, 2
• These patients can be treated entirely with oral antibiotics from the start 3

Patients with Comorbidities or Recent Antibiotic Use

• Comorbidities include: COPD, diabetes, renal failure, congestive heart failure, or malignancy 3
• If no recent antibiotic exposure: Respiratory fluoroquinolone (levofloxacin or moxifloxacin) OR advanced macrolide (azithromycin, clarithromycin) 3, 1
• If recent antibiotic exposure: Use a different antibiotic class than previously prescribed due to resistance risk—options include respiratory fluoroquinolone alone OR advanced macrolide plus high-dose amoxicillin (or amoxicillin-clavulanate) 3, 2

Critical pitfall: Patients recently exposed to one antibiotic class must receive a different class to avoid treatment failure from resistant organisms 2

Hospitalized Non-ICU Patients

Standard regimen options:

• Preferred: β-lactam (ceftriaxone or cefotaxime) PLUS macrolide (azithromycin or clarithromycin) 1, 2, 4
• Alternative: Respiratory fluoroquinolone alone (levofloxacin 750mg daily or moxifloxacin) 3, 1
• Another option: Penicillin G plus macrolide 3

The combination of ceftriaxone plus azithromycin is supported by the most recent high-quality evidence for hospitalized patients 4

Severe CAP/ICU Patients

Without Pseudomonas Risk Factors

• Regimen: Non-antipseudomonal third-generation cephalosporin (ceftriaxone or cefotaxime) PLUS macrolide 3, 1
• Alternative: Moxifloxacin or levofloxacin with or without a non-antipseudomonal cephalosporin 3, 1

With Pseudomonas Risk Factors

Risk factors include: structural lung disease (bronchiectasis), recent hospitalization, recent broad-spectrum antibiotic use, or severe immunosuppression 1

Regimen options:

• Antipseudomonal cephalosporin (ceftazidime, cefepime) OR antipseudomonal penicillin/β-lactamase inhibitor OR carbapenem (meropenem preferred, up to 6g daily) 3, 1
• PLUS ciprofloxacin 3, 1
• OR PLUS macrolide PLUS aminoglycoside (gentamicin, tobramycin, or amikacin) 3, 1

Important caveat: Ceftazidime must be combined with penicillin G for adequate Streptococcus pneumoniae coverage 3

Special Pathogen Considerations

Legionella Species

• Preferred: Levofloxacin or moxifloxacin (most data available for levofloxacin) 3, 1
• Alternative: Azithromycin with or without rifampin 3, 1

Atypical Pathogens (Mycoplasma, Chlamydophila)

• Macrolides, doxycycline, or respiratory fluoroquinolones provide adequate coverage 1, 5

Suspected MRSA

• Add vancomycin or linezolid when community-acquired MRSA is suspected based on prior MRSA infection, recent hospitalization, or recent antibiotic use 2

Duration and Timing

• Initiate antibiotics immediately after diagnosis—delays are associated with increased mortality 1, 2
• First dose timing: For hospitalized patients, administer the first antibiotic dose while still in the emergency department 2
• Minimum duration: 5 days for most patients, provided they are afebrile for 48-72 hours and have no more than one sign of clinical instability 1, 2
• Maximum duration: Generally should not exceed 8 days in responding patients 3, 1
• Extended duration (14-21 days): Required for severe pneumonia or specific pathogens like Legionella, Staphylococcus aureus, or Gram-negative enteric bacilli 2

Transition to Oral Therapy

• Switch criteria: When clinical improvement occurs, temperature has been normal for 24 hours, and patient demonstrates clinical stability 3, 2
• Sequential therapy using the same drug class is safe and effective, even in severe pneumonia 3
• Most patients do not require continued hospitalization after switching to oral antibiotics 3

Common Pitfalls to Avoid

Fluoroquinolone overuse: Reserve fluoroquinolones for patients with β-lactam allergies or specific indications, as overreliance leads to resistance 2. However, the FDA has issued warnings about increasing adverse events with fluoroquinolones, including QT prolongation, tendon rupture, and neurological effects 6

Inadequate atypical coverage: Always ensure coverage for Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila in empiric regimens—this is why macrolides or fluoroquinolones are included 1, 2

Failure to adjust therapy: Once culture results identify a specific pathogen, narrow antimicrobial therapy to target that organism specifically 1, 2

Azithromycin safety concerns: Be aware that azithromycin can cause QT prolongation, hepatotoxicity, and Clostridium difficile-associated diarrhea; use caution in patients with cardiac risk factors 6