Atropine is an anticholinergic agent that prevents the activity of the rest-and-digest response. Atropine is clinically used to treat bradycardia and heart block (AV block). It can also be used to decrease airway secretions before surgery. Side effects of atropine include anticholinergic side effects, such as urinary retention, constipation, dry mouth, blurred vision, dry skin, and fever. Due to its dilating effects on the pupil, atropine can worsen glaucoma and is thus contraindicated in patients with glaucoma. The effects of atropine can be reversed by the drug physostigmine.

Key Points

  • Atropine
    • Mechanism
      • Anticholinergic
        • Inhibits acetylcholine by occupying its receptors
        • Reduces signaling from parasympathetic nervous system
    • Clinical Use
      • Bradycardia
        • Increases heart rate by blocking vagal stimulation
      • Heart block
        • Increases AV nodal conduction by blocking vagal stimulation
      • Reduces oral and respiratory secretions
        • Often used preoperatively (reduces risk of aspiration)
        • Can also be used to treat the “death rattle” associated with end-of-life patients
      • Antidote for cholinergic crisis
        • Decreases acetylcholine signaling
        • Emergency drug to reverse toxic effects of organophosphate (cholinesterase inhibitor) poisoning
      • Pupil dilation for ocular exams
        • Promotes pupil dilation by blocking iris sphincter muscle
    • Side Effects and Adverse Reactions
      • Anticholinergic effects
        •  Stops “rest and digest” system
          • Dry mouth
          • Decreased sweating
            • Teach patient to avoid the heat and hydrate appropriately - decreased perspiration causes the body temperature to rise and puts patient at higher risk for heat stroke
          • Constipation
            • Increase fiber and fluid intake
            • Contraindicated in patients with obstructive GI disorders, paralytic ileus, and ulcerative colitis.
          • Blurred vision, dry eyes
            • Contraindicated in closed angle glaucoma
          • Urinary retention
            • Carefully monitor urine output, especially in elderly patients
          • Mydriasis (dilated pupils)
          • Tachycardia
            • Palpitations
          • Dehydration
          • Dizziness, drowsiness, weakness
          • Confusion, amnesia
      • Palpitations/dysrhythmias
        • Continuous cardiac and BP monitoring
    • Antidote
      • Physostigmine salicylate