Ipratropium bromide

Ipratropium bromide is an anticholinergic bronchodilator and belongs to the class of quaternary ammonium antimuscarinic agents. It inhibits muscarinic acetylcholine receptors, including M₁, M₂, and M₃ receptors, with the M₃ receptor being the primary clinically relevant target. Under normal conditions, acetylcholine released by the parasympathetic nervous system activates M₃ receptors on airway smooth muscle and secretory glands, causing smooth muscle contraction and increased mucus secretion. By blocking M₃ receptors, ipratropium bromide relaxes bronchial smooth muscle, reduces airway resistance, and decreases mucus secretion.