How should chronic cough be evaluated and managed in an adult patient?

Management of Chronic Cough in Adults

Chronic cough (>8 weeks duration) should be managed using a systematic, stepwise algorithmic approach that first excludes red flags, identifies and treats common treatable causes (upper airway cough syndrome, asthma, GERD, eosinophilic bronchitis), and reserves neuromodulators and speech therapy for refractory cases. 1

Initial Assessment and Red Flag Exclusion

Begin by immediately evaluating for life-threatening symptoms, particularly hemoptysis, which requires urgent investigation 1. The initial workup should be focused and include:

• Detailed history: Smoking status, ACE inhibitor use, environmental/occupational exposures, and symptoms suggesting asthma, rhinosinusitis, or GERD 1, 2
• Physical examination: Focus on upper airway and respiratory findings
• Chest X-ray: To exclude masses, interstitial lung disease, or bronchiectasis 3
• Spirometry with bronchodilator testing 2, 3
• Exhaled nitric oxide and blood eosinophil count: To assess for eosinophilic inflammation 2
• Validated cough severity tool: Use instruments like the Leicester Cough Questionnaire to objectively measure impact on quality of life 1

Critical pitfall: Do not pursue extensive diagnostic testing before addressing high-risk factors and attempting empiric treatment for the most common causes 2.

Immediate Actions

If the patient is taking an ACE inhibitor (or sitagliptin), discontinue it immediately and reassess in 4-6 weeks, as drug-induced cough is a common and reversible cause 1, 3. Address smoking cessation if applicable and eliminate environmental/occupational triggers 1.

Common Treatable Causes (The "Big Four")

The most common causes of chronic cough are 1:

1. Upper Airway Cough Syndrome (UACS) - 33% of cases
2. Asthma/Cough Variant Asthma - 16% of cases
3. Gastroesophageal Reflux Disease (GERD)
4. Nonasthmatic Eosinophilic Bronchitis (NAEB) - 5% of cases

Treatment Algorithm for Common Causes

For suspected UACS: Treat empirically with first-generation antihistamines and decongestants for 4-6 weeks 1.

For asthma/eosinophilic inflammation: If spirometry shows obstruction, bronchial hyperresponsiveness is present, or eosinophils are elevated (sputum or blood), initiate inhaled corticosteroids 4. However, if tests for bronchial hyperresponsiveness and eosinophilia are negative, do NOT prescribe inhaled corticosteroids 4.

For GERD: Implement lifestyle modifications (elevate head of bed, avoid late meals, weight loss). Important update: Acid suppression with proton pump inhibitors alone is no longer recommended for cough management 1. If workup is negative for acid reflux, do NOT prescribe PPIs 4. Consider promotility agents for non-acid reflux if appropriate 5.

Follow-up: Reassess patients in 4-6 weeks after initiating treatment 1. Use validated cough tools to objectively measure response.

Unexplained/Refractory Chronic Cough

If cough persists after 4-6 weeks of appropriate treatment for identified causes, the patient has unexplained chronic cough (UCC), which represents cough hypersensitivity syndrome 4, 5. This occurs in 5-10% of patients seeking care for chronic cough 4.

Recognition of Cough Hypersensitivity

Look for characteristic features 5, 6:

• Allotussia: Cough triggered by non-tussive stimuli (perfumes, cold air, talking, laughing)
• Hypertussia: Exaggerated cough response to normal stimuli
• Laryngeal paresthesia: Throat tickle, irritation, or globus sensation

Treatment of Refractory Chronic Cough

The cornerstone of UCC management is multimodal speech pathology therapy 4. This should be offered as first-line treatment for refractory cough when performed by competent practitioners 4, 5.

Neuromodulator Therapy

When speech therapy alone is insufficient or while awaiting access to specialized therapy, consider neuromodulators:

Gabapentin is suggested as a therapeutic trial 4:

• Start at 300 mg once daily
• Titrate upward daily as tolerated
• Maximum dose: 1,800 mg/day in two divided doses
• Critical requirement: Discuss side effects and risk-benefit profile before initiating
• Reassess risk-benefit at 6 months before continuing 4

Low-dose morphine is highly effective in a subset of treatment-resistant patients and may be preferred over gabapentin 5, 7. Pregabalin and amitriptyline are alternatives 7.

Important caveat: The evidence notes that gabapentin and pregabalin are limited by adverse events in clinical practice, despite showing benefit in trials 5.

Emerging Therapies

P2X3 receptor antagonists (gefapixant, eliapixant) represent promising future treatments that target neuronal hypersensitivity by blocking afferent nerve excitability 5, 2, 7. These are currently under investigation.

When to Refer

Consider referral to a specialized cough clinic for 1:

• Refractory unexplained chronic cough despite appropriate trials
• Presence of red flags requiring subspecialty evaluation
• Need for advanced diagnostic testing (bronchoscopy, high-resolution CT)
• Access to specialized speech pathology services

The evidence consistently shows that systematic, protocol-based assessment following these algorithms leads to diagnosis and successful treatment in the majority of patients, with only 5-10% remaining truly refractory 1, 4.