What is the first-line antibiotic for bronchitis?

First-Line Antibiotic for Bronchitis

Antibiotics should NOT be routinely prescribed for acute bronchitis in otherwise healthy adults, as clinical trials have not demonstrated benefit over placebo. 1, 2

When Antibiotics Are NOT Indicated

• Acute uncomplicated bronchitis in healthy adults does not require antibiotic therapy, as most cases are viral in origin and antibiotics provide no significant clinical benefit 1, 2
• Purulent sputum or change in sputum color (green or yellow) does NOT indicate bacterial infection and should not trigger antibiotic prescription 1, 2
• The presence of cough, nasal congestion, or upper respiratory symptoms suggests viral etiology and antibiotics should be avoided 1
• Meta-analyses of randomized controlled trials show no significant reduction in cough duration, illness duration, or work loss with antibiotic treatment 1

Exceptions: When to Consider Antibiotics

Suspected Pertussis

• Antibiotics are indicated during documented pertussis outbreaks to reduce transmission, though they do not hasten symptom resolution if started >7-10 days after illness onset 1
• This is primarily a public health measure rather than for individual clinical benefit 1

Chronic Obstructive Pulmonary Disease (COPD) Exacerbations

• For patients with underlying COPD (FEV1 35-80%), antibiotics are indicated when at least 2 of 3 Anthonisen criteria are present: increased sputum volume, increased sputum purulence, or increased dyspnea 3, 2
• For patients with severe COPD (FEV1 <35%), immediate antibiotic therapy is recommended during exacerbations 2
• Fever persisting >3 days (>38°C) suggests bacterial superinfection and warrants antibiotic consideration 3, 2

First-Line Antibiotic Choice (When Indicated)

Amoxicillin is the first-line antibiotic for acute bacterial bronchitis when treatment is deemed necessary. 2

Primary Options:

• Amoxicillin - reference standard for patients with FEV1 ≥35% and infrequent exacerbations 3, 2
• First-generation cephalosporins - alternative first-line option 3, 2

For Penicillin Allergy:

• Macrolides (azithromycin) 2, 4
• Doxycycline 3, 2
• Pristinamycin 3, 2

Important caveat: One study demonstrated that macrolides (azithromycin) caused significantly more adverse events than placebo in acute bronchitis patients, questioning their routine use 1

Second-Line Options (Treatment Failure)

• Amoxicillin-clavulanate - reference second-line therapy 2
• Second-generation cephalosporins (cefuroxime-axetil) or third-generation (cefpodoxime-proxetil, cefotiam-hexetil) 2
• Respiratory fluoroquinolones (levofloxacin, moxifloxacin) for patients with frequent exacerbations (≥4/year) or FEV1 <35% 2, 5

Target Pathogens

When bacterial infection is suspected, therapy should cover:

• Streptococcus pneumoniae 2
• Haemophilus influenzae 2, 4
• Moraxella catarrhalis 2, 4

Treatment Duration

• Standard antibiotic courses should be at least 7 days 3
• Azithromycin can be given as 500mg daily for 3 days 4, 6

Common Pitfalls to Avoid

• Do not prescribe antibiotics based solely on sputum color or purulence - this reflects inflammatory cells, not bacterial infection 1, 2
• Do not use fluoroquinolones inactive against pneumococci (ofloxacin, ciprofloxacin) or cefixime due to inadequate coverage 2
• Avoid cotrimoxazole due to inconsistent pneumococcal activity and poor benefit/risk ratio 2
• Distinguish acute bronchitis from pneumonia - pneumonia requires different management and is unlikely in immunocompetent adults <70 years without tachycardia (>100 bpm), tachypnea (>24 breaths/min), fever (>38°C), or abnormal chest examination findings 1

Monitoring

• Fever should resolve within 2-3 days of antibiotic initiation 3
• Persistence of fever >38°C after 3 days suggests bacterial pneumonia or treatment failure requiring reevaluation 3, 2
• Clinical reassessment should occur at 5-7 days 3