What treatment options are available for an adult patient with a persistent cough and no known underlying medical conditions?

Management of Persistent Cough in Adults Without Known Underlying Conditions

Initial Approach: Systematic Evaluation Before Treatment

A systematic diagnostic approach targeting the most common causes is essential before initiating symptomatic treatment, as chronic cough typically results from specific treatable conditions rather than requiring empiric cough suppression. 1

Mandatory Initial Workup

• Chest radiograph and spirometry are mandatory for all patients presenting with persistent cough 1
• Detailed history must include occupational exposures, medication use (especially ACE inhibitors), smoking status, and timing/character of cough 1
• Physical examination should concentrate on upper airway (pharyngeal cobblestoning, nasal discharge), chest auscultation, and signs of gastroesophageal reflux 1

Most Common Causes and Treatment Algorithm

First Priority: Upper Airway Cough Syndrome (UACS)

UACS, previously termed postnasal drip, is the most common cause of chronic cough in adults and should be treated first-line with first-generation antihistamine/decongestant combinations. 1, 2

• Start immediately with first-generation antihistamine/decongestant combination (e.g., dexbrompheniramine plus sustained-release pseudoephedrine or azatadine plus sustained-release pseudoephedrine) 2
• Improvement typically occurs within days to 2 weeks 2
• Add intranasal corticosteroids (fluticasone 100-200 mcg daily) for a 1-month trial if no response after 1-2 weeks 1, 2, 3
• Approximately 20% of patients have "silent" UACS with no obvious postnasal drip symptoms yet still respond to treatment 1, 2

Critical caveat: To minimize sedation from first-generation antihistamines, start with once-daily dosing at bedtime for a few days before increasing to twice-daily therapy 2

Second Priority: Asthma/Eosinophilic Bronchitis

If cough persists despite adequate upper airway treatment for 2 weeks, proceed with evaluation for asthma or non-asthmatic eosinophilic bronchitis 4, 2:

• Bronchial provocation testing should be performed in patients with chronic cough and normal spirometry 1
• A 2-week oral corticosteroid trial is recommended - cough is unlikely due to eosinophilic airway inflammation if there is no response 1
• Inhaled corticosteroids are the definitive treatment if eosinophilic inflammation is confirmed 5

Third Priority: Gastroesophageal Reflux Disease (GERD)

Failure to consider GERD as a cause for cough is a common reason for treatment failure, and reflux-associated cough may occur in the absence of gastrointestinal symptoms. 1

• Intensive acid suppression with proton pump inhibitors (omeprazole 20-40 mg twice daily before meals) and alginates should be undertaken for a minimum of 3 months 1, 2
• Improvement in cough from GERD treatment may take up to 3 months 2
• Dietary modifications should accompany pharmacologic therapy 2

Critical Medication Review

In patients with chronic cough taking ACE inhibitors, discontinue therapy with the drug because it is the only uniformly effective treatment for ACE inhibitor-induced cough. 1

• Switch to an angiotensin receptor blocker when indicated, as the incidence of associated cough is similar to control drugs 1
• Cough resolution may be delayed up to 3 months after ACE inhibitor cessation 1

Smoking Cessation

Smoking cessation should be encouraged as it is accompanied by significant remission in cough symptoms - smoking is one of the commonest causes of persistent cough and appears dose-related 1

Symptomatic Treatment Options

For symptomatic relief while pursuing diagnostic evaluation:

• Dextromethorphan is recommended as first-line symptomatic treatment with maximum cough reflex suppression at 60 mg 6, 7
• Simple home remedies like honey and lemon can provide initial relief 1, 6
• Menthol lozenges or vapor may help through cold and menthol-sensitive receptors 6

Important limitation: There are no effective treatments controlling the cough response per se with an acceptable therapeutic ratio - treatment must target the underlying cause 1

When Multiple Causes Coexist

Maintain all partially effective treatments rather than discontinuing them prematurely, as UACS, asthma, and GERD together account for approximately 90% of chronic cough cases. 2

Truly Unexplained Chronic Cough

Only after extensive evaluation ruling out common causes 4:

• Multimodality speech pathology therapy is suggested as a therapeutic trial (Grade 2C) 4
• Gabapentin may be considered, starting at 300 mg once daily up to maximum 1,800 mg daily in divided doses, after discussing potential side effects 4
• Reassess risk-benefit profile at 6 months before continuing gabapentin 4

Red Flags Requiring Urgent Evaluation

Patients should seek immediate medical attention if experiencing 1:

• Coughing up blood
• Breathlessness
• Prolonged fever and feeling unwell
• Symptoms persisting beyond 3 weeks without improvement

Common Pitfalls to Avoid

• Do not diagnose idiopathic cough without thorough specialist evaluation including objective testing for bronchial hyperresponsiveness and eosinophilic bronchitis 4
• Do not use antibiotics for viral upper respiratory infections even when phlegm is present 6
• Do not rely solely on physical examination findings - absence of typical UACS findings doesn't rule out the diagnosis 2
• Do not use topical nasal decongestants for more than 3-5 consecutive days due to risk of rhinitis medicamentosa 2