What are the first line antibiotics for bacterial bronchitis?

First-Line Antibiotics for Bacterial Bronchitis

For acute bacterial bronchitis in otherwise healthy adults, antibiotics should NOT be prescribed, as they provide no proven benefit and cause more harm than good. 1

However, the term "bacterial bronchitis" requires careful clinical distinction, as treatment recommendations differ dramatically based on the specific condition:

Acute Bronchitis in Healthy Adults

No antibiotics are indicated. 2, 1

• The American Thoracic Society explicitly recommends against antibiotic use in acute bronchitis for otherwise healthy adults, as clinical trials have not confirmed benefit versus placebo 1
• Antibiotics should only be considered if fever >38°C persists beyond 3 days, which suggests bacterial superinfection or pneumonia rather than simple acute bronchitis 1
• Purulent or discolored sputum (green/yellow) does NOT indicate bacterial infection and is not an indication for antibiotics 1

Common pitfall: Prescribing antibiotics based on sputum color alone is inappropriate and contributes to antimicrobial resistance 1

Acute Exacerbation of Chronic Bronchitis (COPD Exacerbation)

This is where antibiotics ARE indicated, but only in specific circumstances:

When to Prescribe Antibiotics

Antibiotics are recommended when at least 2 of 3 Anthonisen criteria are present: 2, 3, 1

• Increased sputum volume
• Increased sputum purulence
• Increased dyspnea

Exception: In patients with severe COPD (FEV1 <35%) or respiratory insufficiency, immediate antibiotic therapy is recommended during any exacerbation 1

First-Line Antibiotic Choices

Amoxicillin is the first-choice antibiotic for uncomplicated exacerbations in patients without risk factors (FEV1 ≥35%). 2, 3, 1

• Dosing: 3 g/day in divided doses 2
• This recommendation is based on WHO guidelines, NICE, and multiple international societies 2

Alternative first-line options include: 2, 1

• Doxycycline - particularly useful in penicillin allergy 2
• Macrolides (azithromycin, clarithromycin) - especially for penicillin-allergic patients 2
• First-generation cephalosporins (cefalexin) - though note this is specifically for COPD exacerbations, NOT for other respiratory infections 2

Second-Line Antibiotic Choices

For complicated exacerbations or treatment failure, second-line options include: 2

• Amoxicillin-clavulanate - the reference second-line therapy 2, 1
• Second-generation cephalosporins (cefuroxime-axetil) 2, 1
• Third-generation cephalosporins (cefpodoxime-proxetil, cefotiam-hexetil, but NOT cefixime) 2, 1

Fluoroquinolones: Use with Extreme Caution

Fluoroquinolones (levofloxacin, moxifloxacin) should NOT be used as first-line therapy for bacterial bronchitis. 2

• The FDA issued a boxed warning in 2016 against using fluoroquinolones for acute bacterial exacerbation of chronic bronchitis due to disabling and potentially permanent side effects affecting tendons, muscles, joints, and peripheral/central nervous systems 2
• These agents should be reserved only for life-threatening infections where benefit outweighs risk 2
• The WHO Working Group explicitly excluded fluoroquinolones from recommendations due to side effects and resistance emergence 2

Treatment Duration

Standard treatment duration is 5-8 days for acute exacerbations. 2

• For COPD exacerbations specifically, at least 7 days of treatment is recommended 3
• Clinical reassessment should occur after 5-7 days 3
• Fever should resolve within 2-3 days; persistence beyond 3 days suggests treatment failure or incorrect diagnosis 3

Critical Clinical Algorithm

Step 1: Determine if this is acute bronchitis in a healthy adult or COPD exacerbation

• If healthy adult with acute bronchitis → No antibiotics 1
• If COPD patient → Proceed to Step 2

Step 2: Assess Anthonisen criteria (for COPD patients)

• If <2 criteria present → No antibiotics (unless FEV1 <35%) 2, 3
• If ≥2 criteria present → Proceed to Step 3

Step 3: Assess severity and risk factors

• If FEV1 ≥35%, no complications → Amoxicillin 3 g/day 2, 3
• If penicillin allergy → Doxycycline or macrolide 2
• If treatment failure or complicated → Amoxicillin-clavulanate 2

Step 4: Reassess at 2-3 days

• If fever persists → Consider pneumonia, obtain chest X-ray, consider hospitalization 3
• If improving → Complete 5-8 day course 2, 3