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Library / Pharmacology / Autonomics / Anticholinergics / Ipratropium & Tiotropium

Ipratropium & Tiotropium

Key Board Facts Grid

Target Receptors

M3 antagonist in bronchial smooth muscle

BBB Penetration

Quaternary ammonium; minimal CNS penetration

Primary Indication

COPD maintenance, acute asthma exacerbation add-on therapy

First-Line Antidote

Supportive; physostigmine not usually required due to minimal systemic absorption

Mechanism of Action

  • Competitive M3 antagonism in bronchial smooth muscle.
  • Blocks parasympathetic bronchoconstriction, producing bronchodilation.
  • Tiotropium dissociates slowly from M3, allowing once-daily dosing.
  • Ipratropium is short-acting and used for acute exacerbations.

Adverse Effects & Toxicities

  • Dry mouth is most common.
  • Urinary retention, constipation, blurred vision (less common).
  • Contraindications: hypersensitivity to atropine, narrow-angle glaucoma.
  • Not a rescue inhaler — SABA remains first-line for acute bronchospasm.

DO / OMM Board Pearl

Quaternary M3 antagonists produce T2–T7 viscerosomatic bronchodilation without CNS effects. Useful when parasympathetic tone is elevated in reactive airways.