When are antibiotics indicated for acute bronchitis and what are the recommended first‑line regimens, particularly in patients over 65 years or with chronic lung disease, heart failure, diabetes, immunosuppression, or recent antibiotic use?

Antibiotic Use in Acute Bronchitis

Antibiotics should NOT be prescribed for uncomplicated acute bronchitis in otherwise healthy adults, regardless of cough duration or sputum color, because the illness is viral in 89–95% of cases and antibiotics reduce cough by only half a day while significantly increasing adverse events. 1, 2, 3

Diagnostic Approach: Rule Out Pneumonia First

Before diagnosing acute bronchitis, you must exclude pneumonia by checking vital signs and performing a focused chest examination. 1, 3

Obtain a chest radiograph if ANY of the following are present: 1, 3

• Heart rate >100 beats/min
• Respiratory rate >24 breaths/min
• Oral temperature >38°C
• Abnormal lung findings (crackles, egophony, increased tactile fremitus)

If all four parameters are normal in adults <70 years without comorbidities, pneumonia is unlikely and chest X-ray is not needed. 1

Why Antibiotics Don't Work in Acute Bronchitis

The evidence against routine antibiotics is overwhelming: 1, 2

• Respiratory viruses cause 89–95% of cases
• Antibiotics shorten cough by only 0.5 days (approximately 12 hours)
• Adverse events increase significantly (RR 1.20; 95% CI 1.05–1.36)
• No difference in clinical improvement between antibiotic and placebo groups (RR 1.07; 95% CI 0.99–1.15)

Purulent (green/yellow) sputum occurs in 89–95% of VIRAL cases and does NOT indicate bacterial infection—it reflects inflammatory cells, not bacteria. 1, 2

Cough duration is NOT a marker of bacterial infection—viral bronchitis cough typically lasts 10–14 days and may persist up to 3 weeks. 1, 2, 3

The ONE Exception: Pertussis (Whooping Cough)

When pertussis is confirmed or strongly suspected, prescribe a macrolide antibiotic (azithromycin or erythromycin) immediately. 1, 2, 3

Suspect pertussis when: 1

• Paroxysmal cough
• Post-tussive vomiting
• Inspiratory "whoop"
• Cough lasting >2 weeks

Isolate the patient for 5 days from treatment start; early therapy reduces cough paroxysms and limits transmission. 1, 2

High-Risk Populations: When to Consider Antibiotics

These recommendations apply ONLY to otherwise healthy adults. Patients with the following conditions require a different approach and may need antibiotics: 1, 2, 4

Patients ≥65 Years with Comorbidities

Consider antibiotics in patients ≥65 years with: 1, 4, 5

• Chronic obstructive pulmonary disease (COPD)
• Heart failure
• Insulin-dependent diabetes
• Immunosuppression
• Recent antibiotic use (within 3 months)

Acute Exacerbation of Chronic Bronchitis (AECB)

Prescribe antibiotics when the patient meets ≥2 of the 3 Anthonisen criteria: 1, 5, 6

1. Increased dyspnea
2. Increased sputum volume
3. Increased sputum purulence

AND has ≥1 risk factor: 5, 6

• Age ≥65 years
• FEV₁ <50% predicted
• ≥4 exacerbations in 12 months
• Comorbidities (heart failure, diabetes, immunosuppression)

First-Line Antibiotic Regimens for High-Risk Patients

For moderate-severity AECB: 1, 5, 6

• Doxycycline 100 mg twice daily for 7–10 days, OR
• Amoxicillin/clavulanate 625 mg three times daily for 7–10 days, OR
• Azithromycin 500 mg on day 1, then 250 mg daily for 4 days

For severe AECB (FEV₁ <35%, frequent exacerbations, or risk of Pseudomonas): 1, 5, 6

• High-dose amoxicillin/clavulanate 875 mg twice daily for 10–14 days, OR
• Respiratory fluoroquinolone (levofloxacin 750 mg daily for 5 days)

Critical resistance patterns to remember: 1, 6

• 25% of H. influenzae and 50–70% of M. catarrhalis produce β-lactamase
• Avoid simple aminopenicillins (amoxicillin alone), older macrolides, first-generation cephalosporins, and cotrimoxazole due to increasing resistance

Symptomatic Management for Uncomplicated Acute Bronchitis

Recommended measures: 1, 2, 3

• Antitussives (codeine or dextromethorphan) for bothersome dry cough, especially if disrupting sleep
• Short-acting β₂-agonists (albuterol) ONLY when wheezing accompanies the cough
• Environmental measures: remove irritants (dust, smoke) and use humidified air

NOT recommended (no proven benefit): 1, 2

• Expectorants or mucolytics
• Antihistamines
• Inhaled or oral corticosteroids
• Oral NSAIDs at anti-inflammatory doses
• Routine β₂-agonists without wheezing

Patient Communication Strategy

Effective communication is MORE important for patient satisfaction than prescribing antibiotics. 1, 2, 3

Key points to discuss: 1, 2, 3

1. Expected duration: Cough typically lasts 10–14 days and may persist up to 3 weeks even without antibiotics
2. Viral etiology: The illness is caused by a virus in 89–95% of cases, making antibiotics ineffective
3. Antibiotic risks: Antibiotics cause diarrhea, rash, yeast infections, and contribute to resistance without meaningful benefit
4. Terminology: Refer to the condition as a "chest cold" rather than "bronchitis" to reduce antibiotic expectations

Red-Flag Criteria for Reassessment

Instruct patients to return if: 1, 2

• Fever persists >3 days (suggests bacterial superinfection or pneumonia)
• Cough persists >3 weeks (consider asthma, COPD, pertussis, GERD)
• Symptoms worsen rather than gradually improve

Common Pitfalls to Avoid

Do NOT prescribe antibiotics based on: 1, 2

• Purulent sputum color alone (occurs in 89–95% of viral cases)
• Cough duration alone (viral cough normally lasts 10–14 days)
• Early fever in first 1–3 days (only fever >3 days suggests bacterial superinfection)
• Patient expectation or demand

Approximately one-third of patients labeled with "recurrent acute bronchitis" actually have undiagnosed asthma or COPD—consider spirometry in smokers or those with recurrent episodes. 1

Special Consideration: Pregnancy

In pregnant women requiring antibiotics for bacterial bronchitis, amoxicillin is the preferred agent (FDA Category A, designated "Compatible"). 7

Avoid amoxicillin-clavulanate in women at risk for pre-term delivery due to a very low risk of necrotizing enterocolitis in the fetus. 7

However, remember that >90% of acute bronchitis is viral even in pregnancy, so antibiotics should still be avoided unless pneumonia is suspected or fever persists >3 days. 7