What is the first-line antibiotic for a patient with bronchitis?

First-Line Antibiotic for Bronchitis

For acute bronchitis in previously healthy adults, antibiotics are NOT routinely recommended as this is primarily a viral illness. 1

When Antibiotics Are NOT Indicated

• Previously well adults with acute bronchitis do not require antibiotics in the absence of pneumonia, as acute bronchitis is predominantly viral in etiology 1
• Routine antibiotic treatment is not justified and should not be offered for uncomplicated acute bronchitis 1
• The decision not to prescribe antibiotics should be explained to patients, as many expect antibiotics based on prior experiences 1

When Antibiotics ARE Indicated

Antibiotics should be considered in specific circumstances:

For Acute Exacerbations of Chronic Bronchitis (COPD)

Co-amoxiclav (amoxicillin-clavulanate) 625 mg three times daily orally is the preferred first-line antibiotic for patients with chronic lung disease (particularly COPD) experiencing bacterial exacerbations requiring hospital admission 1

Alternative first-line options include:

• Doxycycline 200 mg loading dose, then 100 mg once daily 1
• Azithromycin 500 mg once daily for 3 days 2, 3, 4

Rationale for Antibiotic Selection

The preferred antibiotics must cover the most likely bacterial pathogens:

• Streptococcus pneumoniae 1
• Haemophilus influenzae 1
• Moraxella catarrhalis 1
• Staphylococcus aureus 1

Co-amoxiclav is preferred because:

• It is a beta-lactamase stable agent effective against all common respiratory pathogens 1
• It provides reliable coverage for H. influenzae, which produces beta-lactamase 1

Doxycycline is an effective alternative:

• Particularly useful for patients with beta-lactam allergies 1
• Provides adequate coverage for typical respiratory pathogens 1

Azithromycin advantages:

• Single daily dosing improves compliance 5, 4
• Short 3-day course (500 mg daily) is as effective as 10-day courses of other antibiotics 3, 4
• Clinical cure rates of 86-92% in acute exacerbations of chronic bronchitis 2, 3
• Better tolerated with fewer gastrointestinal side effects than co-amoxiclav 4

Alternative Antibiotics for Specific Situations

For patients intolerant of first-line options:

• Macrolides: Clarithromycin 500 mg twice daily (preferred over erythromycin for better H. influenzae activity and twice-daily dosing) 1
• Fluoroquinolones: Levofloxacin 500 mg once daily or moxifloxacin 400 mg once daily (reserved for increased likelihood of resistance or local resistance patterns) 1, 6

Important Caveats

Pertussis (Whooping Cough) Exception

If pertussis is suspected or confirmed, a macrolide antibiotic (erythromycin or azithromycin) is mandatory 1

• Treatment must be initiated early (within first few weeks) to reduce coughing paroxysms and prevent disease spread 1
• Patient isolation for 5 days from start of treatment is required 1

Pediatric Considerations

• In children under 3 years with bronchitis requiring antibiotics: amoxicillin 80-100 mg/kg/day in three divided doses 1
• In children over 3 years: macrolides may be considered if atypical pathogens (Mycoplasma or Chlamydia) are suspected 1

Common Pitfalls to Avoid

• Do not prescribe fluoroquinolones as first-line therapy unless there are specific resistance concerns or contraindications to preferred agents 1
• Avoid aminoglycosides in patients with renal impairment due to nephrotoxicity risk 7
• Remember that in vitro resistance may not correlate with clinical failure, particularly for macrolides in chronic suppressive therapy 1
• Bronchodilators are not routinely recommended for acute bronchitis unless wheezing is present 1

Treatment Duration

• Standard antibiotic courses should be at least 7 days for bacterial exacerbations 8
• Azithromycin: 3 days (500 mg daily) is sufficient 2, 3, 4
• Fever should resolve within 2-3 days; persistence beyond 3 days suggests bacterial pneumonia requiring reevaluation 8