Which choline ester is primarily used to diagnose asthma by causing bronchoconstriction?

Methacholine is primarily used in the diagnosis of asthma due to its ability to induce bronchoconstriction, which can help evaluate airway hyperreactivity, a hallmark of asthma. When administered in a controlled testing environment, methacholine causes the airways to constrict, mimicking the symptoms of an asthma attack. This allows healthcare providers to assess the extent of airway reactivity in patients suspected to have asthma. The test is often referred to as a methacholine challenge test.

In contrast, other agents listed serve different purposes. Bethanechol is primarily a muscarinic agonist used to stimulate bladder contractions in the treatment of urinary retention. Pilocarpine is mainly used as a treatment for glaucoma and xerostomia because of its ability to increase salivary secretion. Lastly, atropine is an anticholinergic agent that inhibits muscarinic receptors and would bronchodilate rather than induce bronchoconstriction. Thus, methacholine stands out for its specific diagnostic role in asthma assessments.