Tiotropium

Tiotropium is a long-acting anticholinergic (antimuscarinic) medicine. It binds fairly evenly to all subtypes of muscarinic receptors, from M1 to M5, but its main effect in the airways comes from blocking M3-receptors on the smooth muscle that lines them, which is what allows the airways to widen (bronchodilation). Studies using both human and animal receptors, along with isolated organ tissue, have confirmed that it blocks these receptors in a competitive, reversible way. In laboratory and animal research, it prevented methacholine-induced airway narrowing in a dose-dependent manner, with the effect lasting more than 24 hours. When inhaled, Tiotropium's bronchodilating action occurs mainly at the site where it is deposited in the airways, rather than through effects elsewhere in the body.