Why are bronchodilators given for cough?

Why Bronchodilators Are Given for Cough

Bronchodilators are prescribed for cough primarily when the cough is caused by underlying airway diseases with bronchospasm or airflow obstruction—specifically cough-variant asthma, chronic bronchitis, COPD, and bronchiectasis—where they relieve bronchospasm, reduce airway hyperresponsiveness, and improve mucociliary clearance, thereby reducing cough frequency and severity. 1

Mechanism-Based Rationale

Bronchodilators work through direct relaxation of airway smooth muscle cells, which addresses the pathophysiology underlying cough in obstructive airway diseases. 2, 3 The key mechanisms include:

• Reduction of bronchial hyperresponsiveness: In cough-variant asthma, bronchial hyperresponsiveness is a central feature, and bronchodilators directly address this by relaxing constricted airways. 1
• Improved airway caliber: Experimental studies suggest that increased airway caliber may decrease the sensitivity of cough reflex afferents, though this effect is inconsistent in clinical practice. 4
• Enhanced mucociliary clearance: By opening airways, bronchodilators facilitate secretion mobilization in conditions like chronic bronchitis and bronchiectasis. 1

Disease-Specific Applications

Cough-Variant Asthma (CVA)

Inhaled bronchodilators combined with inhaled corticosteroids are the standard treatment for CVA, with partial improvement often seen after 1 week of bronchodilator therapy alone. 1 However, complete cough resolution typically requires up to 8 weeks of inhaled corticosteroid treatment. 1

• The American College of Chest Physicians gives a Grade A recommendation for treating CVA patients with a standard antiasthmatic regimen of inhaled bronchodilators and inhaled corticosteroids. 1
• A definitive diagnosis of CVA requires documented resolution of cough with specific antiasthmatic therapy, not just the presence of bronchial hyperresponsiveness. 1

Chronic Bronchitis and COPD

Ipratropium bromide (an anticholinergic bronchodilator) receives a Grade A recommendation from the American College of Chest Physicians for improving cough in stable chronic bronchitis, demonstrating more reliable effects than short-acting β-agonists. 5, 6

• Ipratropium bromide at 36 μg (2 inhalations) four times daily reduces cough frequency, cough severity, and sputum volume. 5, 6
• Short-acting β-agonists should be used to control bronchospasm and relieve dyspnea; in some patients, they may also reduce chronic cough (Grade A). 5
• If response to ipratropium is inadequate after 2 weeks, adding a short-acting β-agonist provides additional bronchodilation and potential cough relief. 5, 7

Acute Bronchitis

In most patients with acute bronchitis, β2-agonist bronchodilators should NOT be routinely used to alleviate cough (Grade D recommendation). 1 However, there is an important exception:

• In select adult patients with acute bronchitis who have wheezing accompanying the cough, treatment with β2-agonist bronchodilators may be useful (Grade C). 1
• This distinction is critical: bronchodilators are only beneficial when there is evidence of bronchospasm (wheezing), not for uncomplicated acute bronchitis. 1

Bronchiectasis

In patients with bronchiectasis who have airflow obstruction and/or bronchial hyperreactivity, bronchodilator therapy may be beneficial, though this is based on expert opinion rather than randomized trials. 1

Treatment Algorithm

For patients presenting with chronic cough:

1. Identify the underlying cause through history, physical examination, chest radiograph, and spirometry. 1

2. If cough-variant asthma is suspected:

   • Start inhaled bronchodilators (short-acting β-agonist) for immediate symptom relief. 1
   • Add inhaled corticosteroids for definitive treatment, as bronchodilators alone provide only partial improvement. 1
   • Expect partial improvement within 1 week, complete resolution may take up to 8 weeks. 1

3. If chronic bronchitis/COPD is diagnosed:

   • Initiate ipratropium bromide 36 μg (2 inhalations) four times daily as first-line therapy. 5, 6
   • Add short-acting β-agonist if response is inadequate after 2 weeks. 5
   • For severe airflow obstruction (FEV₁ <50% predicted) or frequent exacerbations, consider LABA/ICS combination. 5

4. If acute bronchitis with wheezing:

   • Trial of β2-agonist bronchodilators is reasonable. 1
   • If no wheezing, bronchodilators are not indicated. 1

Critical Pitfalls and Caveats

The most common mistake is prescribing bronchodilators for cough without evidence of airway obstruction or bronchospasm. 4 Key considerations:

• Bronchodilators are NOT effective for uncomplicated acute bronchitis without wheezing. 1 A Cochrane review found no significant benefit on daily cough scores in patients without baseline airflow obstruction. 1

• In cough-variant asthma, bronchodilators alone are insufficient—inhaled corticosteroids are essential for complete cough resolution. 1

• Inhaled corticosteroids themselves can paradoxically induce or exacerbate cough due to aerosol constituents, particularly with beclomethasone dipropionate compared to triamcinolone acetonide. 1 Consider switching formulations if this occurs. 1

• The evidence for bronchodilators specifically treating cough is inconsistent in humans, and their effects are more reliably demonstrated for dyspnea and airflow obstruction than for cough per se. 4

• Long-term monotherapy with inhaled corticosteroids is not recommended for chronic bronchitis; bronchodilators should be the foundation of therapy. 5

When Bronchodilators Should NOT Be Used for Cough

• Uncomplicated acute bronchitis without wheezing (Grade D recommendation). 1
• Cough due to gastroesophageal reflux, rhinitis, or other non-bronchospastic causes—these require different targeted therapies. 1
• Postinfectious cough may mimic asthma with transient bronchial hyperresponsiveness, but this is self-limited and does not represent true asthma. 1