bronchodilater

A bronchodilator is a medication that relaxes the smooth muscle lining the airways, widening the bronchi and improving airflow. Bronchodilators are a central part of treatment for obstructive airway diseases such as asthma and chronic obstructive pulmonary disease (COPD). They are designed to provide rapid relief of symptoms or long-term maintenance of airway openness.

Bronchodilators are commonly grouped into three main categories: beta-2 adrenergic agonists, anticholinergics (muscarinic antagonists), and methylxanthines. Beta-2 agonists stimulate receptors on airway smooth muscle to increase cyclic AMP and cause relaxation. They are subdivided into short-acting (SABA) agents, such as albuterol, and long-acting (LABA) agents, such as salmeterol and formoterol. Anticholinergics block muscarinic receptors, reducing acetylcholine-induced bronchoconstriction; short-acting ipratropium and long-acting tiotropium are commonly used. Theophylline, a methylxanthine, works through multiple mechanisms including phosphodiesterase inhibition and adenosine receptor antagonism, but is used less frequently due to a narrow therapeutic window and drug interactions.

Inhalation is the preferred route because it delivers the drug directly to the lungs and minimizes systemic effects. Short-acting inhaled formulations provide quick relief of acute symptoms, while long-acting agents are used for ongoing maintenance, often in combination with anti-inflammatory therapies. In asthma, LABAs are generally prescribed only with inhaled corticosteroids. In COPD, long-acting agents, including both LABAs and long-acting muscarinic antagonists, are common maintenance options.

Side effects vary by class but can include tachycardia, tremor, and palpitations with beta-agonists; dry mouth or urinary retention with anticholinergics; and potential nausea or arrhythmias with methylxanthines. Bronchodilators address symptoms and airflow limitation but do not replace anti-inflammatory treatments.