– Tiotropium Bromide hydrate (BA-679 BR hydrate) is a potent anticholinergic and bronchodilator, serving as a muscarinic receptor antagonist, specifically targeting mAChR. It is developed for treating chronic obstructive airways disease (COPD), demonstrating novel and long-lasting effects. Binding studies with [3H]tiotropium bromide in human lung reveal its high potency and equivalent affinity for M1-, M2-, and M3-receptors, making it roughly 10 times more effective than ipratropium bromide. It notably inhibits cholinergic nerve-induced contraction of both guinea-pig and human airways more potently than atropine or ipratropium bromide, albeit with a slower onset. Tiotropium bromide uniquely presents slow dissociation from M3-receptors on airway smooth muscle and rapid dissociation from M2 autoreceptors on cholinergic nerve terminals. As a quaternary ammonium derivative, it shows high affinity and special kinetic selectivity towards muscarinic receptors across M1-, M2-, and M3-subtypes, due to its slower dissociation from M1- and M3-receptors compared to M2-receptors.