Bronchoconstrictive

Bronchoconstrictive describes anything that causes bronchoconstriction, the narrowing of the airways due to contraction of the bronchial smooth muscle. This constriction increases airway resistance and can impair airflow, especially during expiration. Bronchoconstriction can occur as part of normal reflex responses or in pathological conditions such as asthma or chronic obstructive pulmonary disease.

Mechanisms and mediators contributing to bronchoconstriction include activation of the parasympathetic nervous system, with acetylcholine acting on M3 muscarinic receptors on airway smooth muscle. Inflammatory mediators released during allergic reactions—such as histamine and leukotrienes (LTC4, LTD4, LTE4), as well as prostaglandin D2—also promote constriction. Sensory nerves and reflex pathways can further amplify the response. Nonimmune triggers, including cold air, exercise, smoke, and environmental irritants, may provoke bronchoconstriction through direct or indirect mechanisms. In diseases with airway hyperresponsiveness, these constrictive responses can be exaggerated.

Bronchoconstrictive agents and tests are used to study and diagnose conditions. Agents such as methacholine and histamine are employed in bronchial provocation tests to assess airway responsiveness, helping to diagnose asthma or monitor disease activity.

Clinical significance and management involve avoiding triggers when possible and using pharmacologic therapies to counteract constriction and reduce inflammation. Bronchodilators, particularly inhaled beta-agonists, are commonly used to relieve acute bronchoconstriction. Anticholinergic agents, corticosteroids, and leukotriene modifiers may be employed to reduce ongoing airway narrowing and inflammation.