What is the recommended evaluation and treatment for a persistent dry cough?

Treatment for Persistent Dry Cough

The most effective treatment for persistent dry cough is to identify and treat the underlying cause systematically, starting with discontinuation of ACE inhibitors if present, followed by trials for upper airway cough syndrome (UACS), asthma/eosinophilic bronchitis, and gastroesophageal reflux disease (GERD) in that order. 1

Immediate Action: Medication Review

• Stop ACE inhibitors immediately if the patient is taking them, as this is the only uniformly effective treatment for ACE inhibitor-induced cough, which occurs in 5-35% of patients on these medications 1
• Cough typically resolves within 1-4 weeks after cessation, though it may persist up to 3 months in some cases 1
• Switch to an angiotensin receptor blocker (ARB), as most patients with ACE inhibitor-associated cough can tolerate ARBs without recurrence 1
• Do not try substituting with a different ACE inhibitor, as cough will almost always recur since this is a class effect 2

Systematic Diagnostic and Treatment Algorithm

First: Treat Upper Airway Cough Syndrome (UACS)

• Start a first-generation antihistamine-decongestant combination (such as brompheniramine/pseudoephedrine or chlorpheniramine/phenylephrine) 1
• Add an intranasal corticosteroid spray (fluticasone or mometasone) 1
• Expected response time: days to 1-2 weeks 1
• UACS is suggested by postnasal drip sensation, throat clearing, nasal discharge, or cough triggered by phonation (talking, laughing, singing) 1

Second: Treat Asthma or Eosinophilic Bronchitis

• Perform bronchial provocation testing (methacholine challenge) if available and spirometry is normal 1
• If testing unavailable or positive, initiate inhaled corticosteroids (fluticasone 220 mcg or budesonide 360 mcg twice daily) plus short-acting beta-agonists 1
• Consider adding a leukotriene inhibitor before escalating to oral steroids 1
• For patients not responding to inhaled therapy, prescribe oral prednisone 40 mg daily for 5-10 days 1
• Expected response time: up to 8 weeks for full effect 1
• Cough may be the only manifestation of asthma, with no wheezing or dyspnea 1

Third: Treat Gastroesophageal Reflux Disease (GERD)

• Initiate high-dose proton pump inhibitor therapy (omeprazole 40 mg twice daily or equivalent) 1
• Add prokinetic therapy if there is little or no response to PPI alone 1
• Implement dietary modifications: avoid late meals, elevate head of bed, reduce fatty foods, caffeine, alcohol, and chocolate 1
• Expected response time: 2 weeks to several months (highly variable) 1
• GERD can cause cough without any gastrointestinal symptoms in up to 75% of cases 3
• Cough triggered by eating, postprandial timing, or phonation suggests GERD 1

Symptomatic Treatment Options

For Older Adults or When Investigating Underlying Cause

• Dextromethorphan 60 mg combined with guaifenesin provides maximum cough reflex suppression and is superior to standard over-the-counter doses of 15-30 mg 4
• Benzonatate 100-200 mg three to four times daily acts peripherally to anesthetize stretch receptors in the lungs 4
• Honey with lemon may be effective for benign viral cough and should be considered before pharmacological treatments 4

For Chronic Idiopathic Cough (After All Causes Ruled Out)

• Low-dose morphine has been shown useful when other treatments fail 4
• This should only be considered after thorough evaluation at a specialist cough clinic 1

Critical Pitfalls to Avoid

• Do not assume timing rules out ACE inhibitors: Consider ACE inhibitors as causative regardless of temporal relationship between drug initiation and cough onset, as cough can begin hours to over a year after starting therapy 1
• Do not use second-generation antihistamines for UACS: First-generation sedating antihistamines are significantly more effective than newer non-sedating agents for non-histamine-mediated postnasal drip 3
• Do not stop treatments prematurely: Chronic cough is frequently multifactorial, and partial improvement with one treatment means continuing that therapy while adding the next intervention, not stopping and switching 1
• Do not prescribe antibiotics for persistent dry cough unless there is clear evidence of bacterial infection, as most cases are not infectious 1

When to Escalate Evaluation

• Order chest radiograph and spirometry as mandatory baseline tests 1
• Obtain high-resolution CT chest if all empiric therapies fail and chest X-ray is normal 1
• Consider bronchoscopy if complete workup fails, to evaluate for endobronchial lesions, sarcoidosis, or eosinophilic bronchitis 1
• Perform 24-hour esophageal pH monitoring if GERD is suspected but empiric therapy fails, though interpretation can be challenging 1, 3

Red Flags Requiring Urgent Evaluation

• Hemoptysis (coughing up blood) requires urgent evaluation 4
• Dyspnea (shortness of breath) requires urgent evaluation 4
• Prolonged fever and general malaise require urgent evaluation 4
• Weight loss or night sweats suggest serious underlying pathology 1

Expected Timeline for Treatment Response

• UACS treatment: days to 1-2 weeks 1
• Asthma treatment: up to 8 weeks 1
• GERD treatment: 2 weeks to several months 1
• ACE inhibitor cessation: 1-4 weeks (up to 3 months) 1

The key principle is that most persistent dry cough has an identifiable and treatable cause, and systematic evaluation with adequate treatment trials is more effective than symptomatic suppression alone. 1, 5, 6