Community-Acquired Pneumonia Antibiotic Selection in Penicillin-Allergic Patients

Introduction to Antibiotic Selection

The American Thoracic Society and Infectious Diseases Society of America recommend a respiratory fluoroquinolone (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) as the preferred first-line monotherapy for penicillin-allergic patients with community-acquired pneumonia, with macrolides (azithromycin or clarithromycin) reserved only for outpatients without comorbidities in areas with macrolide resistance <25% 1, 2

For previously healthy patients without comorbidities, a respiratory fluoroquinolone is the preferred option: levofloxacin 750 mg once daily for 5 days or moxifloxacin 400 mg once daily for 7-10 days 1, 2
Macrolide monotherapy (azithromycin 500 mg day 1, then 250 mg daily for days 2-5) is acceptable only if there is no recent antibiotic use within 3 months, local macrolide-resistant S. pneumoniae prevalence is <25%, and no comorbidities 2, 3
Doxycycline 100 mg twice daily for 7-10 days is an alternative option 1

Respiratory fluoroquinolone monotherapy is the treatment of choice: levofloxacin 750 mg IV/PO daily or moxifloxacin 400 mg IV/PO daily 1, 2
The 2019 ATS/IDSA guidelines explicitly state that a respiratory fluoroquinolone should be used for penicillin-allergic patients in the hospital setting 2

For penicillin-allergic patients with severe CAP requiring ICU admission, a combination of respiratory fluoroquinolone (levofloxacin 750 mg IV daily or moxifloxacin 400 mg IV daily) and aztreonam (1-2 g IV every 8 hours) is recommended 2
If MRSA is suspected, add vancomycin 15-20 mg/kg IV every 8-12 hours or linezolid 600 mg IV every 12 hours 2

Azithromycin can be used in pediatric patients ≥5 years old: 10 mg/kg day 1 (max 500 mg), then 5 mg/kg daily days 2-5 (max 250 mg) 5
Clarithromycin can be used in pediatric patients ≥5 years old: 15 mg/kg/day in 2 divided doses (max 1 g/day) 5

Do not use azithromycin monotherapy if the patient received antibiotics in the past 3 months, as this selects for resistant organisms 3
In regions with macrolide-resistant S. pneumoniae ≥25%, macrolide monotherapy has unacceptably high failure rates 2, 3
Screen for cardiac risk factors and obtain ECG before initiating fluoroquinolones in patients with arrhythmia history 1

Clinical review at 48 hours or earlier if clinically indicated 6
Repeat chest radiograph at 6 weeks for patients with persistent symptoms, smokers, or those >50 years old 4, 6