A patient with COPD is prescribed an inhaled anticholinergic bronchodilator. Ipratropium is preferred over systemic atropine because ipratropium:

• A Has greater affinity for M1 receptors specifically in bronchial smooth muscle
• B Is a quaternary compound with minimal systemic absorption after inhalation, reducing systemic side effects ✓
• C Is a selective M3 antagonist without affecting other muscarinic subtypes
• D Stimulates beta-2 receptors in addition to blocking muscarinic receptors

Explanation

Ipratropium is a quaternary derivative of atropine; when inhaled, its ionized (charged) form is poorly absorbed through the bronchial mucosa and essentially not absorbed from the GI tract if swallowed, minimizing systemic anticholinergic side effects such as tachycardia, urinary retention, and dry mouth. It produces local bronchodilation via M3 muscarinic blockade in airways. Tiotropium is more M3/M1-selective, but ipratropium blocks all muscarinic subtypes.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.