What are the types of bronchodilators?

Types of Bronchodilators

Bronchodilators are classified into three major categories: beta-2 agonists, anticholinergics (muscarinic antagonists), and methylxanthines, each with different mechanisms of action and duration of effect. 1, 2, 3

Beta-2 Agonists

Short-Acting Beta-2 Agonists (SABAs)

• Examples include albuterol, levalbuterol, and pirbuterol 1
• Primary treatment for quick relief of acute symptoms and prevention of exercise-induced bronchoconstriction (EIB) 1
• Onset of action within minutes, duration 4-6 hours 1
• Increasing use of SABA treatment or use >2 days/week for symptom relief generally indicates inadequate asthma control 1
• Regular scheduled daily use is not recommended 1

Long-Acting Beta-2 Agonists (LABAs)

• Examples include salmeterol, formoterol, indacaterol, olodaterol, and vilanterol 1, 3
• Provide bronchodilation for at least 12 hours after a single dose 1
• Used in combination with inhaled corticosteroids (ICS) for long-term control in moderate or severe persistent asthma 1, 4
• Should never be used as monotherapy for long-term asthma control due to safety concerns 1, 4
• May be used before exercise to prevent EIB, but duration does not exceed 5 hours with chronic use 1
• In COPD, LABAs can be used as maintenance therapy 1

Anticholinergics (Muscarinic Antagonists)

Short-Acting Muscarinic Antagonists (SAMAs)

• Primary example is ipratropium bromide 1
• Inhibit muscarinic cholinergic receptors and reduce intrinsic vagal tone of the airway 1
• Provide additive benefit to SABAs in moderate or severe exacerbations in emergency settings 1
• May be used as alternative bronchodilators for patients who do not tolerate SABAs 1
• Typically administered every 6 hours during moderate or severe asthma exacerbations 1

Long-Acting Muscarinic Antagonists (LAMAs)

• Examples include tiotropium, aclidinium, umeclidinium, and glycopyrronium 1, 3
• May be beneficial in patients with symptoms of breathlessness in bronchiectasis 1
• In COPD, LAMAs are recommended as maintenance therapy 1
• Limited evidence for use in asthma, but may provide benefit when added to ICS 1

Methylxanthines

• Primary example is theophylline 1, 5
• Sustained-release theophylline is a mild to moderate bronchodilator 1
• Used as alternative (not preferred) therapy for step 2 care in mild persistent asthma or as adjunctive therapy with ICS 1
• May have mild anti-inflammatory effects 1
• Monitoring of serum theophylline concentration is essential due to narrow therapeutic window 1, 5
• Dosing is weight-based and should be calculated on ideal body weight 5
• Therapeutic serum concentration range is 10-14.9 mcg/mL for optimal effect 5

Combination Therapy

• Combination of bronchodilators from different classes can provide additive effects 6, 7
• LABA/ICS combinations (e.g., salmeterol/fluticasone, formoterol/budesonide) are preferred for asthma control 4, 8
• LAMA/LABA combinations provide optimal bronchodilation by affecting both arms of the autonomic nervous system 7
• In COPD, a SAMA plus SABA is more effective than SABA alone for preventing acute exacerbations 1
• Triple therapy (LAMA/LABA/ICS) in a single inhaler is now available for severe asthma and COPD 7

Clinical Considerations

• Inhaled route is preferred to minimize systemic effects 3
• Fast- and short-acting agents are best for symptom rescue, while long-acting agents are preferred for maintenance therapy 3
• Once-daily dosing improves adherence to treatment regimens 3
• Reversibility testing to bronchodilators may help identify patients with co-existing asthma but is not required to benefit from bronchodilator therapy 1
• For patients with bronchiectasis and co-existing COPD or asthma, bronchodilator treatment should follow the respective guideline recommendations 1

Emerging Bronchodilator Classes

• Novel PDE inhibitors 2, 9
• Natural phytotherapeutics 2
• Bitter taste receptor ligands 2
• Chloride channel modulators 2
• Bifunctional drugs with dual pharmacological actions in a single molecule 7

These emerging classes have the potential to be used alone or in combination with existing bronchodilators to improve management of airway disorders 2, 9, 7.