What are the contraindications for atropine?

Contraindications for Atropine

Atropine is absolutely contraindicated in narrow-angle (closed-angle) glaucoma because it causes pupillary dilation that can precipitate acute glaucoma attacks by blocking the drainage angle of the eye. 1

Absolute Contraindications

Narrow-Angle Glaucoma

• The American College of Cardiology specifically lists narrow-angle glaucoma as a contraindication to atropine use, including for procedures like stress echocardiography 1
• Atropine-induced mydriasis (pupillary dilation) blocks the drainage angle, precipitating acute angle-closure attacks 1
• This applies to both systemic and topical ophthalmic atropine administration 1

Post-Heart Transplant Patients

• Atropine should not be used in patients who have undergone heart transplant without evidence of autonomic reinnervation (Class III: Harm recommendation) 2
• The denervated transplanted heart lacks parasympathetic innervation, making atropine ineffective and potentially harmful 2

Relative Contraindications and Cautions

Coronary Artery Disease

• The American College of Cardiology warns that atropine-induced tachycardia poses significant risk in patients with coronary artery disease by increasing myocardial oxygen demand 3
• Total dosing should be restricted to avoid detrimental cardiac effects, with maximum cumulative doses of 2.5-3 mg 4, 2
• In acute myocardial infarction, atropine should be used cautiously due to potential loss of protective parasympathetic tone 2

Open-Angle Glaucoma

• The American College of Cardiology recommends caution (though not absolute contraindication) in patients with open-angle glaucoma 1
• Elevation of intraocular pressure has been reported as a potential side effect 5

Hypersensitivity

• Hypersensitivity to atropine or other anticholinergic agents is a contraindication 4

Important Clinical Pitfalls

Paradoxical Bradycardia with Low Doses

• Doses below 0.5 mg can cause paradoxical bradycardia due to central vagotonic effects at the sinoatrial node 6
• Always use doses of at least 0.5-1 mg IV to avoid this effect 4, 2

Monitoring Requirements

• Monitor for anticholinergic toxicity symptoms including fever, confusion, hallucinations, tachycardia, dry mouth, and delirium 3
• Cardiac dysrhythmias including atrial fibrillation and supraventricular tachycardia can occur even with ophthalmic administration 7
• Children under 3 years may be more susceptible to systemic side effects 4

Type II AV Block

• Atropine is rarely appropriate for type II second-degree AV block, as it may paradoxically worsen the block by increasing sinus rate while failing to improve AV conduction 4