Lecture 13 — Muscarinic Blocking Drugs
Core mechanism
Antimuscarinic drugs competitively block acetylcholine (ACh) at muscarinic receptors without activating them. They inhibit parasympathetic muscarinic effects.
Drugs named in the lecture
Atropine; cyclopentolate; dicyclomine; glycopyrrolate; ipratropium; oxybutynin; propantheline; scopolamine; tolterodine; tropicamide.
Cardiovascular uses
Atropine can reverse pronounced vagally mediated bradycardia. The slides discuss vasovagal attacks and hyperactive carotid sinus syndrome as causes of marked slowing of the heart.
Gastrointestinal and urinary effects
The lecture describes atropine with diphenoxylate (Lomotil) for diarrhea/hypermotility. Muscarinic antagonists reduce detrusor contraction and can relieve urinary urgency, but can also cause urinary retention.
Cholinergic poisoning
Atropine opposes muscarinic effects from cholinesterase inhibitors and muscarine-containing mushrooms. The lecture notes that large doses may be needed after potent organophosphate exposure.
Anticholinergic toxicity
Belladonna/atropine poisoning features dry mouth, hot or flushed skin, reduced sweating, dilated pupils, blurred vision, urinary difficulty, tachycardia, agitation, hallucinations and delirium.
Other poisoning sources
The lecture lists antihistamines, antiparkinsonian agents, antipsychotics, antispasmodics, and belladonna alkaloids as possible sources of anticholinergic toxicity.
