Recommended Antibiotics for Community-Acquired Pneumonia (CAP)
For outpatients with CAP, the recommended first-line treatment is amoxicillin 1 g every 8 hours or doxycycline 100 mg twice daily for patients without comorbidities, while patients with comorbidities should receive either a respiratory fluoroquinolone (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) or a combination of a β-lactam plus a macrolide. 1, 2
Outpatient Treatment
Patients without comorbidities:
- Amoxicillin 1 g every 8 hours 1
- OR Doxycycline 100 mg twice daily (some experts recommend an initial dose of 200 mg) 1
Patients with comorbidities:
- Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) 1, 3, 4
- OR Combination therapy with a β-lactam plus a macrolide (azithromycin 500 mg daily or clarithromycin 500 mg twice daily) 1, 2, 5
Inpatient Treatment (Non-ICU)
- Combination therapy with a β-lactam (ampicillin + sulbactam 1.5–3 g every 6 h, cefotaxime 1–2 g every 8 h, ceftriaxone 1–2 g daily, or ceftaroline 600 mg every 12 h) plus a macrolide (azithromycin 500 mg daily or clarithromycin 500 mg twice daily) (strong recommendation, high quality evidence) 1
- OR Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) (strong recommendation, high quality evidence) 1
- For patients with contraindications to both macrolides and fluoroquinolones: β-lactam plus doxycycline 100 mg twice daily (conditional recommendation, low quality evidence) 1
Severe CAP (ICU Treatment)
- β-lactam (cefotaxime, ceftriaxone, or ampicillin-sulbactam) plus either azithromycin or a respiratory fluoroquinolone 2
Special Considerations
- If a patient has received antibiotics within the previous 3 months, select an antibiotic from a different class due to increased risk of bacterial resistance 1, 2
- For regions with high rates (>25%) of macrolide-resistant S. pneumoniae, consider alternative regimens even for patients without comorbidities 2
- Fluoroquinolones provide coverage for both typical and atypical pathogens with high lung penetration and low resistance rates, but carry risk of adverse events 1, 6
- For patients with risk factors for MRSA or P. aeruginosa, specific coverage for these pathogens may be required 1
Pathogens and Coverage
- Common bacterial pathogens in CAP include Streptococcus pneumoniae, Haemophilus influenzae, Chlamydia pneumoniae, and Staphylococcus aureus 1, 3
- Atypical pathogens include Mycoplasma pneumoniae, Legionella pneumophila, and Chlamydophila pneumoniae 1, 7
- Respiratory fluoroquinolones provide coverage against both typical and atypical pathogens, including multi-drug resistant S. pneumoniae (MDRSP) 3, 4
- Macrolides are effective against atypical pathogens but increasing resistance in S. pneumoniae is concerning 5, 8
Duration of Treatment
- Treatment duration should generally not exceed 8 days in responding patients 2
- Short-course regimens with azithromycin, fluoroquinolones, or telithromycin have shown efficacy and may improve compliance 6
Common Pitfalls and Caveats
- Differentiating between "typical" and "atypical" pneumonia based on clinical presentation alone is difficult and unreliable 9
- Initial empiric therapy should cover both typical and atypical pathogens, especially in hospitalized patients 9
- Despite the concern regarding adverse events with fluoroquinolones (tendon rupture, peripheral neuropathy, CNS effects), they remain justified for adults with comorbidities due to their efficacy, coverage spectrum, and convenience of monotherapy 1
- A systematic review found no significant mortality benefit with atypical coverage compared to typical coverage only, but this mainly compared quinolone monotherapy to β-lactams 10
- Newer antibiotics including lefamulin and omadacycline show promise for CAP treatment, especially against resistant pathogens, but require further validation in outpatient settings 1, 8