What is the recommended treatment for a patient with left lung infiltrate indicative of pneumonia who is allergic to penicillin (PCN)?

Treatment of Pneumonia in Patients with Penicillin Allergy

For patients with left lung infiltrate (pneumonia) who are allergic to penicillin, a respiratory fluoroquinolone such as levofloxacin 750 mg daily is the recommended first-line treatment. 1

Initial Assessment and Treatment Selection

When treating pneumonia in a patient with penicillin allergy, consider:

• Severity of pneumonia (outpatient vs. hospitalized vs. ICU)
• Type of penicillin allergy (immediate-type hypersensitivity vs. non-immediate)
• Likely pathogens based on clinical presentation

Outpatient Treatment Options

For mild to moderate community-acquired pneumonia in penicillin-allergic patients:

• First choice: Respiratory fluoroquinolone monotherapy

  • Levofloxacin 750 mg once daily for 5 days
  • Moxifloxacin 400 mg once daily for 7 days 1

• Alternative options:

  • Doxycycline 100 mg twice daily
  • For atypical pathogens: Azithromycin 500 mg on day 1, then 250 mg daily for 4 days 1

Hospitalized Non-ICU Patients

For hospitalized patients with moderate to severe pneumonia:

• Preferred regimen: Levofloxacin 750 mg IV/PO daily 1
• Duration: 5-7 days (minimum 5 days, should be afebrile for 48-72 hours with no more than one sign of clinical instability)

ICU Patients

For critically ill patients with severe pneumonia:

• Preferred regimen: Aztreonam plus either azithromycin 500 mg IV daily or a respiratory fluoroquinolone 1
• If gram-negative coverage is needed: Aztreonam 2 g IV every 8 hours plus levofloxacin 750 mg IV daily 1

Special Considerations

Immediate-Type Hypersensitivity to Penicillin

Patients with history of immediate-type hypersensitivity reactions (hives, bronchospasm) should avoid all β-lactams and carbapenems. Use:

• Fluoroquinolone monotherapy (levofloxacin or moxifloxacin) 2, 1
• Alternative: Aztreonam plus a macrolide or fluoroquinolone 2

Suspected Atypical Pathogens

If clinical presentation suggests atypical pathogens (Mycoplasma, Chlamydophila, Legionella):

• Levofloxacin 750 mg daily is particularly effective against these organisms 1, 3

Suspected Pseudomonas Infection

For patients at risk for Pseudomonas aeruginosa:

• Aztreonam 2 g IV every 8 hours plus levofloxacin 750 mg IV daily 1

Duration of Therapy

• Standard duration: 5-7 days for most patients 1
• Minimum treatment duration: 5 days, with criteria for discontinuing including:
  • Afebrile for 48-72 hours
  • No more than one sign of clinical instability
  • Improvement in cough and dyspnea 1

Potential Pitfalls and Caveats

1. Fluoroquinolone resistance: Although uncommon, fluoroquinolone-resistant S. pneumoniae has been reported. Consider alternative therapy if patient has received multiple courses of fluoroquinolones in the past 4, 5.

2. Avoid fluoroquinolone prophylaxis: Patients receiving fluoroquinolone prophylaxis should not receive empirical therapy with a fluoroquinolone 2.

3. Switching from IV to oral: Patients can be switched from IV to oral antibiotics when they are hemodynamically stable, clinically improving, able to take oral medications, and afebrile for 48-72 hours 1.

4. Anaerobic coverage: For suspected aspiration pneumonia, consider adding anaerobic coverage with clindamycin or metronidazole if using a fluoroquinolone that lacks anaerobic activity 1.

5. MRSA consideration: If MRSA is suspected, add vancomycin or linezolid to the treatment regimen 1.

Levofloxacin has demonstrated excellent clinical efficacy in community-acquired pneumonia with a convenient once-daily dosing schedule and good safety profile, making it an ideal choice for penicillin-allergic patients 3, 6.