Tiotropium differs from ipratropium in COPD management primarily because of which kinetic property at muscarinic receptors?

• A Tiotropium dissociates rapidly from M3 receptors allowing dose titration
• B Tiotropium is an irreversible antagonist at muscarinic receptors
• C Tiotropium dissociates slowly from M3 receptors giving prolonged bronchodilation suitable for once-daily dosing ✓
• D Tiotropium selectively blocks M2 autoreceptors enhancing acetylcholine release

Explanation

Tiotropium exhibits kinetic selectivity: it dissociates slowly from M3 muscarinic receptors but rapidly from M2 receptors. This gives it a long duration of bronchodilation and allows once-daily dosing. It is not irreversible. Its M3 slow dissociation, not M2 selectivity, is the key advantage over ipratropium.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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