metakolin

Metakolin (also spelled metacholine; chemical name methacholine) is a synthetic choline ester and a muscarinic receptor agonist. It acts primarily at M3 receptors on airway smooth muscle to induce bronchoconstriction and is most commonly encountered in clinical and research settings as an inhaled bronchial challenge agent to assess airway hyperresponsiveness.

In medicine, metakolin is used in controlled provocation tests (methacholine challenge tests) to help diagnose asthma and evaluate the degree of airway sensitivity. During such tests, progressively increasing inhaled doses produce a measurable decrease in lung function in susceptible individuals; results are interpreted alongside clinical history and other investigations. Because it induces reversible bronchospasm, metakolin is a diagnostic tool rather than a therapeutic agent.

Pharmacologically, metakolin is a quaternary ammonium compound that is rapidly hydrolyzed by cholinesterases, conferring a short duration of action. Common effects relate to its cholinergic activity and include cough and bronchospasm; systemic adverse effects are uncommon at diagnostic doses but can include bradycardia or sweating at higher exposures.

Use of metakolin is contraindicated or used with caution in patients with recent myocardial infarction, stroke, uncontrolled hypertension, or severely compromised respiratory function. Testing is performed under medical supervision with equipment and medications available to manage acute bronchospasm.