Ipratropium Bromide action is to:

• A. Blocks histamine receptors
• B. Stimulates beta-2 receptors
• C. Antagonizes acetylcholine at muscarinic receptors, causing bronchodilation and decreased secretions
• D. Inhibits leukotriene synthesis

Answer: (C)

This question tests how ipratropium works as an inhaled bronchodilator. It acts as a competitive antagonist of acetylcholine at muscarinic receptors in the airways, especially the M3 receptors on airway smooth muscle and glands. By blocking parasympathetic stimulation, it prevents acetylcholine-induced bronchoconstriction and reduces glandular secretions, leading to bronchodilation and drier airways. It’s a short-acting antimuscarinic agent often used as an adjunct in COPD and can be combined with beta-agonists for additive relief. It does not block histamine receptors, does not stimulate beta-2 receptors, and does not inhibit leukotriene synthesis. Its inhaled form limits systemic effects and provides quicker, localized airway effects.