Treatment for Community-Acquired Pneumonia
Outpatient Treatment (Non-Hospitalized Patients)
For previously healthy outpatients under 40 years old without comorbidities or recent antibiotic use, start with a macrolide (azithromycin 500 mg Day 1, then 250 mg Days 2-5) as first-line monotherapy 1, 2, 3.
For outpatients over 40 years old or those with comorbidities (diabetes, heart disease, COPD, chronic kidney disease), use either:
Patients with recent antibiotic exposure (within 3 months) should receive antibiotics from a different class to avoid resistance 2
Doxycycline 100 mg twice daily (with first dose of 200 mg) is an acceptable alternative for outpatients without comorbidities 2
Critical Outpatient Pitfall
Reserve fluoroquinolones for patients with true β-lactam allergies or specific indications, as overuse drives resistance development 2. The FDA has issued warnings about increasing adverse events with fluoroquinolones, including tendon rupture, peripheral neuropathy, and CNS effects 2, 4.
Hospitalized Non-ICU Patients
For hospitalized non-ICU patients, the standard regimen is a β-lactam (ceftriaxone 1-2 g every 24 hours) PLUS a macrolide (azithromycin or clarithromycin) 1, 2, 5.
Alternative monotherapy: respiratory fluoroquinolone alone (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) 1, 2
The first antibiotic dose must be administered in the emergency department before hospital admission, as delays are associated with increased mortality 2
Administer the initial dose within 4-6 hours of presentation for optimal outcomes 2, 5
Severe CAP/ICU Patients
For ICU patients without Pseudomonas risk factors, use a β-lactam (ceftriaxone, cefotaxime, or ampicillin-sulbactam) PLUS either azithromycin OR a respiratory fluoroquinolone 1, 2.
Pseudomonas Coverage Required When:
- Structural lung disease (bronchiectasis)
- Recent hospitalization with IV antibiotics in past 90 days
- Severe COPD requiring chronic steroids or frequent antibiotics 2
For patients with Pseudomonas risk factors, use an antipseudomonal β-lactam (piperacillin-tazobactam, cefepime, imipenem, or meropenem) PLUS either:
- Ciprofloxacin 400 mg IV every 8-12 hours OR levofloxacin 750 mg daily, OR
- An aminoglycoside (gentamicin, tobramycin, or amikacin) PLUS azithromycin 1, 2
MRSA Coverage
Add vancomycin 15-20 mg/kg every 8-12 hours OR linezolid 600 mg every 12 hours when community-acquired MRSA is suspected 2, particularly with:
- Prior MRSA infection or colonization
- Recent hospitalization (within 90 days)
- IV drug use
- Necrotizing or cavitary pneumonia on imaging 2
Duration of Therapy
Treat for a minimum of 5 days, ensuring the patient is afebrile for 48-72 hours and has no more than 1 sign of clinical instability before discontinuation 1, 2.
For uncomplicated Streptococcus pneumoniae pneumonia: 7-10 days is typically sufficient 2
For severe pneumonia or specific pathogens (Legionella, Staphylococcus aureus, Gram-negative enteric bacilli): extend treatment to 14-21 days 2
Treatment generally should not exceed 8 days in a responding patient without complications 2
Switching from IV to Oral Therapy
Switch from intravenous to oral antibiotics when the patient is hemodynamically stable, clinically improving, able to take oral medications, and has been afebrile for 24 hours 1, 2.
This typically occurs around Day 3 of hospitalization 2
Switching to oral therapy does not mandate immediate discharge; complete the antibiotic course as clinically appropriate 2
Pathogen-Directed Therapy
Once a specific pathogen is identified through reliable microbiological methods (blood cultures, sputum cultures, urinary antigen tests), narrow antimicrobial therapy to target that organism 1, 2.
Only 38% of hospitalized CAP patients have a pathogen identified 5
Of those with identified pathogens, up to 40% are viral (influenza, COVID-19, RSV), and approximately 15% are Streptococcus pneumoniae 5
All patients should be tested for COVID-19 and influenza when these viruses are circulating in the community, as positive results may change management to include antiviral therapy 5
Special Considerations
Macrolide Resistance
Streptococcus pneumoniae resistance to macrolides ranges 30-40% and often co-exists with β-lactam resistance 2. This is why combination therapy (β-lactam plus macrolide) is preferred over macrolide monotherapy in hospitalized patients, as the β-lactam provides pneumococcal coverage while the macrolide covers atypical pathogens 2, 5.
Atypical Pathogen Coverage
While mortality benefit from empirical atypical coverage is not definitively proven, clinical success is significantly higher when atypical antibiotics are used for Legionella, Mycoplasma pneumoniae, and Chlamydophila pneumoniae 2. The macrolide or fluoroquinolone component of combination therapy addresses these organisms 1, 2.
Corticosteroids in Severe CAP
Systemic corticosteroid administration within 24 hours of severe CAP development may reduce 28-day mortality 5. Consider methylprednisolone 0.5 mg/kg every 12 hours for 5 days in patients with severe CAP requiring ICU admission 5.
Follow-Up
Clinical review should be arranged for all patients at approximately 6 weeks post-discharge, either with their primary care physician or in a hospital clinic 1, to ensure complete resolution and identify any complications or alternative diagnoses.