Ipratropium bromide is used as a bronchodilator in COPD. It differs from tiotropium in that ipratropium:
- A Is a selective M3 antagonist with a 24-hour duration of action suitable for once-daily dosing
- B Crosses the blood-brain barrier and causes significant CNS anticholinergic adverse effects
- C Is a non-selective muscarinic antagonist with short duration (4–6 hours), requiring multiple daily doses, and dissociates rapidly from M2 receptors ✓
- D Has systemic bioavailability of 40% after inhalation, requiring dose adjustment in renal impairment
Explanation
Ipratropium bromide is a non-selective short-acting muscarinic antagonist (SAMA) with a duration of 4–6 hours; its rapid dissociation from all muscarinic receptor subtypes (including the presynaptic M2 inhibitory autoreceptors on airway nerves) results in shorter action compared with tiotropium. Tiotropium is a long-acting muscarinic antagonist (LAMA) with kinetic selectivity for M3 (slow dissociation from M3, rapid from M2), allowing once-daily dosing and 24-hour bronchodilation. Both have negligible systemic absorption and CNS effects due to quaternary ammonium structure.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.