bronchodilator

Bronchodilators are medicines that relax the smooth muscle in the walls of the airways, widening the bronchi and improving airflow. They are a foundational treatment for obstructive airway diseases such as asthma and chronic obstructive pulmonary disease (COPD).

Most bronchodilators work by relaxing airway smooth muscle through different mechanisms: beta-2 adrenergic agonists stimulate β2 receptors, increasing intracellular cyclic AMP and causing muscle relaxation; anticholinergic agents block muscarinic receptors (primarily M3) to reduce bronchoconstriction; methylxanthines inhibit phosphodiesterase enzymes, raising cAMP levels.

Key agents include short-acting beta-agonists (SABA) such as albuterol, and long-acting beta-agonists (LABA) such as salmeterol and formoterol. Inhaled anticholinergics include ipratropium (short-acting) and tiotropium (long-acting). Methylxanthines like theophylline are used less commonly today. Many regimens combine inhaled corticosteroids with LABA for asthma, and LAMA/LABA combinations are used for COPD.

Inhalation is the preferred route for most patients because it delivers the drug to the airways with fewer systemic effects. Oral or intravenous forms are used in some settings, including severe exacerbations or when inhalation is not feasible.

Common side effects include tremor, tachycardia, and nervousness from beta-agonists; dry mouth and urinary retention from anticholinergics; and potential nausea or arrhythmias with methylxanthines. Patients should use the correct device technique and be monitored for response and adverse effects.