What is the evaluation and treatment approach for a persistent dry cough lasting more than one month?

Evaluation and Management of Persistent Dry Cough Lasting More Than One Month

For a dry cough persisting beyond one month, systematically evaluate and treat the three most common causes in sequence: upper airway cough syndrome (UACS), asthma, and gastroesophageal reflux disease (GERD), which together account for approximately 90% of chronic cough cases. 1

Initial Assessment and Red Flags

Obtain a chest radiograph immediately to exclude pneumonia, structural abnormalities, masses, interstitial disease, or congestive heart failure. 1 This is mandatory in the evaluation of chronic cough. 2

Critical historical elements to assess:

• ACE inhibitor use: Stop the medication regardless of temporal relationship, as cough may resolve within days to 2 weeks (median 26 days). 2
• Smoking status: Chronic bronchitis from smoking typically resolves within 4 weeks of cessation in most patients. 2
• Systemic symptoms: Fever, night sweats, weight loss, or history of tuberculosis, cancer, or AIDS require expanded differential diagnosis. 2
• Duration classification: Cough lasting >8 weeks qualifies as chronic cough in adults. 2, 1

Systematic Treatment Algorithm

Step 1: Treat Upper Airway Cough Syndrome (UACS)

Initiate empiric therapy with a first-generation antihistamine-decongestant combination (e.g., chlorpheniramine with pseudoephedrine) for 1-2 weeks. 1, 3

Look for these clinical pointers:

• Nasal discharge, throat clearing, or postnasal drip sensation 1
• Nasal congestion or rhinorrhea 3

Step 2: Evaluate and Treat Asthma

If UACS treatment fails after 1-2 weeks, proceed to asthma evaluation. 1, 3

Perform spirometry with bronchodilator response or bronchoprovocation challenge. 1 If testing is unavailable, initiate an empiric trial of inhaled bronchodilators and/or inhaled corticosteroids. 1

Suspect asthma when:

• Cough worsens at night, with cold air exposure, or with exercise 2, 1
• Response to bronchodilators occurs within 1 week, with complete resolution potentially taking up to 8 weeks 3

Step 3: Treat Gastroesophageal Reflux Disease (GERD)

If both UACS and asthma treatments fail, initiate intensive GERD therapy even without typical heartburn symptoms, as up to 75% of patients with GERD-related cough lack classic reflux symptoms. 3

Comprehensive anti-reflux regimen includes: 1, 3

• High-dose PPI therapy: Omeprazole 40mg once daily (or equivalent) taken before meals 3
• Dietary modifications: Limit fat to <45g/24 hours; eliminate coffee, tea, soda, chocolate, mints, citrus (including tomatoes), and alcohol 3
• Lifestyle changes: Avoid eating 2-3 hours before bedtime, elevate head of bed, weight management, smoking cessation 3

GERD therapy requires patience: Response may take 2 weeks to several months, with some patients requiring 8-12 weeks before improvement. 3, 4 This contrasts with UACS or asthma, which typically respond within 1-2 weeks. 3

If minimal improvement after 4-8 weeks:

• Escalate to twice-daily PPI dosing (e.g., omeprazole 20-40mg twice daily) 3, 4
• Add prokinetic agent such as metoclopramide 3, 4

Advanced Diagnostic Testing

Proceed to advanced testing only after adequate therapeutic trials of the above three conditions have failed. 1

Order these investigations: 1

• High-resolution CT (HRCT) chest: Evaluate for bronchiectasis, interstitial lung disease, or occult masses
• 24-hour esophageal pH monitoring: Most sensitive and specific test for GERD-related cough if empiric therapy failed
• Bronchoscopy: Evaluate for endobronchial lesions, sarcoidosis, eosinophilic bronchitis, or occult infection

Treatment of Refractory Chronic Cough

Only diagnose unexplained cough after completing systematic evaluation and adequate therapeutic trials of all common causes. 2, 1

For truly refractory cough:

• Consider gabapentin trial starting at 300mg once daily, escalating as tolerated to maximum 1,800mg daily in divided doses. 1
• Multimodality speech pathology therapy is a reasonable alternative approach. 1
• Low-dose morphine may be considered but carries addiction risk. 2

Critical Pitfalls to Avoid

• Do not assume purulent sputum indicates bacterial infection requiring antibiotics in chronic cough—this is typically from airway inflammation, not infection. 1
• Do not stop therapy prematurely: UACS and asthma typically respond within 1-2 weeks, but GERD may require 2-3 months. 1, 3
• Recognize multiple simultaneous causes: Up to 25% of patients have more than one contributing condition requiring combined therapy. 1
• Do not prescribe inhaled corticosteroids if bronchial hyperresponsiveness and eosinophilia testing are negative. 1
• Do not continue PPIs indefinitely if objective testing for acid reflux is negative. 1

Special Consideration: Post-Infectious Cough

If cough began with an acute respiratory infection 3-8 weeks ago, consider post-infectious cough. 2

Treatment options include: 2

• Inhaled ipratropium as first-line therapy
• Inhaled corticosteroids if ipratropium fails and cough adversely affects quality of life
• Short course of oral prednisone (30-40mg daily) for severe paroxysms after ruling out other causes
• Central-acting antitussives (codeine or dextromethorphan) when other measures fail