When to Use Atropine
Atropine is primarily indicated for temporary blockade of severe or life-threatening muscarinic effects, including as an antisialagogue, an antivagal agent, an antidote for organophosphorus or muscarinic mushroom poisoning, and to treat bradyasystolic cardiac arrest. 1
Cardiovascular Indications
Bradycardia Management
- Symptomatic sinus bradycardia (heart rate less than 50 bpm associated with hypotension, ischemia, or escape ventricular arrhythmia) 2
- Most effective for sinus bradycardia occurring within 6 hours of onset of acute myocardial infarction symptoms 2
- Bradycardia may be related to ischemia, reperfusion (Bezold-Jarish reflex), ischemic-type chest discomfort, or morphine/nitroglycerin therapy 2
- Particularly useful when bradycardia is associated with reduced cardiac output and signs of peripheral hypoperfusion (arterial hypotension, confusion, faintness, grayish pallor) 2, 3
Conduction Disorders
- Symptomatic AV block occurring at the AV nodal level (second-degree type I or third degree with a narrow-complex escape rhythm) 2
- Type I second-degree AV block, especially when complicating inferior myocardial infarction 2
- When AV block or sinus bradycardia is associated with congestive heart failure, hypotension, or frequent and complex ventricular arrhythmias 2
Cardiac Arrest
Other Medical Indications
- Antidote for organophosphorus or muscarinic mushroom poisoning 1, 4
- As an antisialagogue (to reduce secretions) 1
- As an adjunct to morphine administration to reduce nausea and vomiting 2
- Premedication in specific emergency intubations when there is higher risk of bradycardia (e.g., when giving succinylcholine as a neuromuscular blocker) 2
Dosing Guidelines
For Bradycardia
- Initial dose: 0.5 mg intravenously 2
- Repeat if needed every 5 minutes 2
- Maximum total dose: 2.0 mg 2
- Titrate to achieve minimally effective heart rate (approximately 60 bpm) 2
For Ventricular Asystole
- Initial dose: 1 mg intravenously 2
- Repeat in 5 minutes if asystole persists (while continuing CPR) 2
- Total cumulative dose should not exceed 2.5 mg over 2.5 hours 2
For Organophosphorus Poisoning
Special Populations
- In patients with coronary artery disease: Limit the total dose to 0.03-0.04 mg/kg 1
- For pediatric emergency intubation: 0.02 mg/kg with no minimum dose 2
Contraindications and Precautions
When NOT to Use Atropine
- Atrioventricular block occurring at an infranodal level (usually associated with anterior MI with a wide-complex escape rhythm) 2
- Asymptomatic sinus bradycardia 2
- Type II second-degree AV block (atropine is rarely effective) 2
- In patients who have undergone cardiac transplantation without evidence of autonomic reinnervation 3
Important Precautions
- Use with caution in acute MI due to the protective effect of parasympathetic tone against ventricular fibrillation and myocardial infarct extension 2
- Doses less than 0.5 mg may paradoxically result in further slowing of heart rate due to central reflex stimulation of the vagus or peripheral parasympathomimetic effect 2, 3
- Monitor for adverse effects including tachycardia, dilated pupils, blurred vision, light sensitivity, and dry mouth 1, 5
- Severe adverse effects correlate with either higher initial doses (1.0 mg vs. the usual 0.5 mg) or total cumulative doses exceeding 2.5 mg over 2.5 hours 6
Potential Adverse Effects
- Common side effects: dryness of the mouth, blurred vision, photophobia, and tachycardia 1
- Serious adverse effects: ventricular tachycardia or fibrillation, sustained sinus tachycardia, increased premature ventricular contractions, and toxic psychosis 6
- Central nervous system effects with repeated administration: hallucinations and fever 2, 5
- Allergic reactions (rare): local manifestations or systemic anaphylaxis 7