Pharmacology of anti-asthmatic drugs

Pharmacology of anti-asthmatic drugs

Pharmacology of Anti-Asthmatic Drugs explains mechanisms and actions of drugs used to relieve bronchoconstriction and airway inflammation.

Main Classes of Anti-Asthmatic Drugs

1. Bronchodilators

   • These drugs relieve bronchoconstriction and are primarily used in acute asthma attacks.

     1. β2-Adrenergic Agonists

        • Examples: Salbutamol (short-acting), Salmeterol (long-acting)
        • Mechanism: Stimulate β2-receptors in bronchial smooth muscle → ↑ cAMP → bronchodilation
        • Use:
          • Short-acting (SABA): Rescue inhaler in acute attack
          • Long-acting (LABA): Maintenance therapy (usually with corticosteroids)

     2. Anticholinergics (Muscarinic antagonists)

        • Examples: Ipratropium (short-acting), Tiotropium (long-acting)
        • Mechanism: Block M3 receptors → inhibit vagal-mediated bronchoconstriction
        • Use: More commonly used in COPD, but can be adjunct in asthma

     3. Methylxanthines

        • Example: Theophylline
        • Mechanism: Inhibits phosphodiesterase → ↑ cAMP → bronchodilation; also has anti-inflammatory effect
        • Use: Less commonly used due to narrow therapeutic index and side effects

2. Anti-inflammatory Agents

   • These control the underlying inflammation in chronic asthma.

     1. Corticosteroids

        • Examples: Beclomethasone (inhaled), Prednisolone (oral)
        • Mechanism: Inhibit inflammatory gene expression, reduce cytokine production
        • Use:
          • Inhaled: Maintenance therapy
          • Oral: For severe or uncontrolled asthma

     2. Leukotriene Receptor Antagonists (LTRAs)

        • Examples: Montelukast, Zafirlukast
        • Mechanism: Block leukotriene receptors → reduce bronchoconstriction, mucus secretion, and inflammation
        • Use: Add-on therapy, especially useful in aspirin-sensitive or exercise-induced asthma

     3. Mast Cell Stabilizers

        • Examples: Cromolyn sodium
        • Mechanism: Prevent mast cell degranulation → reduce histamine and leukotriene release
        • Use: Prophylaxis; rarely used now

3. Biologics (Monoclonal Antibodies)

   • Target specific mediators of inflammation in severe asthma.

     1. Anti-IgE

        • Example: Omalizumab
        • Mechanism: Binds to IgE → prevents activation of mast cells
        • Use: Severe allergic asthma not controlled by other drugs

     2. Anti-IL-5 / Anti-IL-4 Receptor

        • Examples: Mepolizumab, Dupilumab
        • Mechanism: Inhibit IL-5 or IL-4/IL-13 pathways → reduce eosinophilic inflammation
        • Use: Severe eosinophilic asthma

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