Skip to content
Tenderpoints™Hub
Library / Pharmacology / Autonomics / Anticholinergics / Atropine

Atropine

Key Board Facts Grid

Target Receptors

Non-selective M1–M5 muscarinic antagonist

BBB Penetration

Tertiary amine; crosses the BBB at high doses

Primary Indication

Symptomatic bradycardia, high-grade AV block, organophosphate poisoning muscarinic effects

First-Line Antidote

Physostigmine for isolated anticholinergic toxidrome

Mechanism of Action

  • Competitive antagonism at all muscarinic ACh receptors.
  • M2 blockade in SA/AV nodes increases heart rate and AV conduction.
  • M3 blockade produces mydriasis, cycloplegia, dry mouth, urinary retention, decreased GI motility.
  • M3 sweat-gland blockade causes anhidrosis and hyperthermia.
  • No nicotinic receptor blockade at usual clinical doses.

Adverse Effects & Toxicities

  • Classic anticholinergic toxidrome: delirium, mydriasis, cycloplegia, dry mouth, urinary retention, constipation, tachycardia, hyperthermia.
  • Can precipitate acute angle-closure glaucoma in shallow anterior chambers.
  • Infants are especially prone to hyperthermia; elderly to delirium.
  • Contraindications: narrow-angle glaucoma, severe BPH/urinary retention, GI obstruction, paralytic ileus, tachycardia.

DO / OMM Board Pearl

Blunts vagal tone (CN X) at the SA and AV nodes. Mimics a relative sympathetic state. In OMT, this correlates with reduced parasympathetic influence over cardiopulmonary structures T1–T5.