What is the next step for a 3-week cough in an adult patient who has completed a course of amoxicillin (amoxicillin)?

Next Step for 3-Week Cough After Completing Amoxicillin

For an adult with a 3-week cough who has completed amoxicillin, initiate inhaled ipratropium bromide as first-line therapy while actively ruling out pertussis if any paroxysmal features are present. 1, 2

Immediate Assessment Required

Rule Out Pertussis First

• Actively screen for pertussis, which accounts for approximately 10% of chronic cough cases and is often underdiagnosed in adults 2
• Obtain nasopharyngeal culture or PCR immediately if the patient has any of these features: 1, 2
  • Paroxysmal coughing (sudden, uncontrollable coughing fits)
  • Post-tussive vomiting (vomiting after coughing episodes)
  • Inspiratory whooping sound
• If pertussis is confirmed or highly suspected, prescribe macrolide antibiotics immediately (azithromycin or clarithromycin) to reduce coughing severity and prevent transmission, and isolate the patient for 5 days from treatment start 1

Screen for Red Flags

Before proceeding with treatment, assess for concerning features that require urgent expanded workup: 2

• Hemoptysis
• Fever, night sweats, or significant weight loss
• History of tuberculosis, cancer, or immunosuppression
• In smokers: finger clubbing, which may suggest bronchogenic carcinoma 2

Primary Treatment Approach

First-Line Therapy: Inhaled Ipratropium Bromide

• Prescribe inhaled ipratropium bromide as the evidence-based first-line treatment for post-infectious cough at 3 weeks duration 1, 2
• This anticholinergic bronchodilator has demonstrated efficacy in controlled trials for subacute post-infectious cough 2
• Provide reassurance that post-infectious cough typically resolves spontaneously within 3-8 weeks total from symptom onset 2

What NOT to Do

• Do NOT prescribe additional antibiotics unless bacterial sinusitis or pertussis is confirmed—the amoxicillin course was appropriate initial therapy, and further antibiotics are not indicated for post-infectious cough 2, 3
• Purulent sputum does NOT indicate bacterial infection and should not prompt antibiotic prescription 1

Diagnostic Testing at This Stage

Obtain Chest Radiograph

• Order a chest X-ray to exclude pneumonia, malignancy, tuberculosis, bronchiectasis, and interstitial lung disease 2
• Approximately 31% of chest radiographs in persistent cough will be abnormal or yield a diagnosis 2

Consider Spirometry

• Perform spirometry with bronchodilator response testing to evaluate for asthma or airflow obstruction 2
• Measure FEV1 before and after short-acting β2-agonist 2
• Important caveat: Normal spirometry does NOT exclude asthma or eosinophilic bronchitis 2

Follow-Up Strategy

Reassess in 2 Weeks

• If ipratropium fails after 2 weeks, begin evaluation for: 1
  • Asthma or non-asthmatic eosinophilic bronchitis
  • Gastroesophageal reflux disease (GERD)
  • Upper airway cough syndrome (post-nasal drip)

Critical Timeline Threshold

• At 8 weeks total duration, the cough must be reclassified as chronic cough requiring different evaluation 4, 2
• Schedule follow-up in 4-6 weeks to reassess if cough persists 1, 4

Common Underlying Mechanisms at 3 Weeks

Post-infectious cough at this stage is associated with: 4

• Postviral airway inflammation (48.4% of cases)
• Upper airway cough syndrome (33.2% of cases)
• Cough-variant asthma (15.8% of cases)
• Nonasthmatic eosinophilic bronchitis (5.4% of cases)

Key Clinical Pitfalls to Avoid

• Failing to consider pertussis in adults with prolonged cough—this is frequently underdiagnosed 4, 2
• Inappropriately prescribing additional antibiotics for non-bacterial post-infectious cough 4, 2
• Failing to recognize the 8-week threshold where post-infectious cough becomes chronic cough requiring different evaluation 2
• Abandoning GERD therapy prematurely if initiated—it may require 8-12 weeks for response 2