What to prescribe for a patient with chronic cough, considering inhaled corticosteroids and dextromethorphan?

Treatment of Chronic Cough with Inhaled Corticosteroids and Dextromethorphan

For chronic cough, inhaled corticosteroids should be prescribed as first-line therapy when asthma or eosinophilic bronchitis is identified, while dextromethorphan should be reserved as a symptomatic measure only after other treatments have failed. 1, 2

Diagnostic Framework Before Prescribing

Before initiating treatment, you must identify the underlying cause through systematic evaluation:

• Rule out common causes first: upper airway cough syndrome, asthma, gastroesophageal reflux disease, and ACE inhibitor use must be excluded or treated before attributing cough to other etiologies 1, 3
• Confirm airway hyperresponsiveness: bronchial challenge testing (methacholine) distinguishes cough variant asthma from non-asthmatic eosinophilic bronchitis 1, 2
• Assess eosinophilic inflammation: sputum eosinophil counts or fractional exhaled nitric oxide (FENO) predict corticosteroid responsiveness and guide therapy 1, 2
• Obtain chest radiography: exclude interstitial lung disease, sarcoidosis, or structural abnormalities 3

When to Prescribe Inhaled Corticosteroids

Cough Variant Asthma (First-Line Treatment)

Inhaled corticosteroids are the definitive first-line treatment for cough variant asthma and should be initiated immediately upon diagnosis. 1, 2

• Starting dose: beclomethasone 200-800 μg daily equivalent (or fluticasone 100-500 μg twice daily), using twice-daily dosing with proper inhaler technique 2, 4
• Treatment duration: continue for 4-8 weeks initially while monitoring symptom response 2
• Combination therapy: add a long-acting beta-agonist to inhaled corticosteroids for enhanced efficacy, as this combination provides superior improvements in cough symptoms, pulmonary function, and airway inflammation compared to beta-agonist alone 1, 5

Stepwise Escalation Algorithm

If cough persists after initial inhaled corticosteroid therapy:

1. Increase inhaled corticosteroid dose up to 2000 μg beclomethasone daily equivalent 1, 2
2. Add leukotriene receptor antagonist (montelukast) - this combination has specific evidence supporting efficacy in cough variant asthma 1, 2
3. Consider short-course oral corticosteroids (prednisone 30-40 mg daily for 1-2 weeks) only after maximizing inhaled therapy, then transition back to inhaled corticosteroids 1, 2

Non-Asthmatic Eosinophilic Bronchitis

• Inhaled corticosteroids are first-choice treatment with the same dosing strategy as cough variant asthma 1
• Escalation pathway: if response is incomplete, increase inhaled corticosteroid dose and add leukotriene receptor antagonist before considering oral steroids 1

Postinfectious Cough

Do not start with inhaled corticosteroids for postinfectious cough. 1

• First-line: trial of inhaled ipratropium bromide 1, 3
• Second-line: inhaled corticosteroids only if cough persists despite ipratropium and adversely affects quality of life 1
• Severe paroxysms: prednisone 30-40 mg daily for a short, finite period after ruling out upper airway cough syndrome, asthma, and GERD 1

When to Prescribe Dextromethorphan

Dextromethorphan should be considered only when other measures fail, as it provides symptomatic relief without addressing underlying inflammation. 1

Appropriate Clinical Scenarios

• Postinfectious cough: central acting antitussives such as dextromethorphan should be considered when inhaled ipratropium and inhaled corticosteroids fail 1
• Refractory chronic cough: after specific treatments for identified causes have been exhausted 6, 7
• Palliative care settings: for distressing cough in advanced illness when disease-directed treatment is not feasible 7

Dosing and Efficacy Considerations

• Standard dose: 20 mg dextromethorphan is similarly effective to 20 mg codeine in reducing cough frequency, but dextromethorphan lowers cough intensity to a greater degree 8
• Advantages over codeine: dextromethorphan has fewer side effects, greater safety in overdose, and non-narcotic status 8
• Limitations: high doses may be required for efficacy, and effectiveness in chronic cough is modest at best 6

Critical Pitfalls to Avoid

• Do not prescribe dextromethorphan as first-line therapy: it masks symptoms without treating underlying inflammation and delays appropriate diagnosis 1, 6
• Do not use oral corticosteroids before trying inhaled corticosteroids: this violates guideline-based stepwise therapy and exposes patients to unnecessary systemic side effects 2, 3
• Do not prescribe inhaled corticosteroids for unexplained chronic cough: if testing for bronchial hyperresponsiveness and eosinophilia is negative, steroids are not indicated 3
• Do not continue anti-inflammatory therapy intermittently: stopping or interrupting inhaled corticosteroids in cough variant asthma causes worsening of disease with return to baseline inflammation 5
• Ensure proper inhaler technique: apparent treatment failure is often due to poor technique or non-adherence rather than true medication ineffectiveness 2

Practical Treatment Algorithm

For chronic cough with suspected asthma or eosinophilic inflammation:

1. Confirm diagnosis with bronchial challenge testing and/or eosinophil assessment 1, 2
2. Start inhaled corticosteroids (beclomethasone 200-800 μg daily equivalent) for 4-8 weeks 2
3. If incomplete response, increase dose to 2000 μg daily equivalent and add leukotriene receptor antagonist 1, 2
4. If still refractory, consider short-course oral prednisone 30 mg daily for 1-2 weeks, then return to inhaled therapy 2
5. Reserve dextromethorphan for symptomatic relief only after above measures fail 1

For postinfectious cough:

1. Start inhaled ipratropium bromide 1, 3
2. Add inhaled corticosteroids if cough persists and affects quality of life 1
3. Consider dextromethorphan when other measures fail 1