Pharmacology · single question
What is the mechanism of action of ipratropium?
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Correct answer: A. Muscarinic receptor antagonist
- A. Correct. Ipratropium is a quaternary ammonium ANTIMUSCARINIC (anticholinergic) bronchodilator used in asthma and, especially, COPD. Blocking M3 receptors on bronchial smooth muscle produces bronchodilation and reduces mucus secretion. Dental relevance: its anticholinergic action causes XEROSTOMIA, raising caries and candidiasis risk.
- B. A muscarinic agonist would INCREASE bronchial secretions and cause bronchoconstriction — the opposite of what is wanted in obstructive airway disease.
- C. A cholinergic agonist (e.g., pilocarpine) increases secretions — pilocarpine is in fact used to TREAT dry mouth, the opposite effect.
- D. Nicotinic receptors sit at the neuromuscular junction and autonomic ganglia; blocking them causes paralysis, not bronchodilation.