Recommended First Dose of Atropine for Bradycardia in Adults
The recommended first dose of atropine for treating symptomatic bradycardia in adults is 0.5 mg IV, which can be repeated every 3-5 minutes to a maximum total dose of 3 mg. 1, 2
Indications for Atropine Use
Atropine is indicated for:
- Symptomatic sinus bradycardia (generally heart rate less than 50 bpm associated with hypotension, ischemia, or escape ventricular arrhythmia) 1
- Symptomatic AV block occurring at the AV nodal level (second-degree type I or third-degree with narrow-complex escape rhythm) 1
- Ventricular asystole 1
- Bradycardia with evidence of hemodynamic compromise (hypotension, altered mental status, chest pain, acute heart failure, or shock) 1
Administration Guidelines
Dosing Protocol
- Initial dose: 0.5 mg IV 1, 2
- Repeat every 3-5 minutes as needed 1
- Maximum total dose: 3 mg 1
- Administer by rapid IV push 2
Important Considerations
- Doses less than 0.5 mg may paradoxically worsen bradycardia due to central vagal stimulation 1
- Titrate to achieve minimally effective heart rate (approximately 60 bpm) 1
- In patients with coronary artery disease, limit total dose to 0.03-0.04 mg/kg 2
- Peak action occurs within 3 minutes of IV administration 1
Cautions and Contraindications
Atropine should be used with caution in:
- Acute coronary ischemia or myocardial infarction (increased heart rate may worsen ischemia or increase infarct size) 1
- Patients who have undergone cardiac transplantation (may cause paradoxical slowing of heart rate) 1
- Type II second-degree or third-degree AV block with new wide-QRS complex (block likely at infranodal level) 1
Atropine is generally ineffective in:
- AV block occurring at infranodal level (usually associated with anterior MI with wide-complex escape rhythm) 1, 3
- Cardiac transplant patients due to lack of vagal innervation 1
Alternative Treatments When Atropine Is Ineffective
If atropine is ineffective or contraindicated:
- Consider transcutaneous pacing (TCP) for unstable patients not responding to atropine 1
- β-adrenergic support (dopamine, epinephrine) can be used as temporizing measures while preparing for transvenous pacing 1
- Immediate pacing might be considered in unstable patients with high-degree AV block when IV access is not available 1
Potential Adverse Effects
- Tachycardia (may worsen ischemia in patients with acute coronary syndrome) 2, 4
- Ventricular tachycardia or fibrillation (rare) 1, 4
- Central nervous system effects including hallucinations and fever with repeated administration 1
- Paradoxical worsening of bradycardia with doses <0.5 mg 1
- Dry mouth, blurred vision, and photophobia (with chronic administration) 2
Special Populations
Patients with Coronary Artery Disease
- Limit total dose to 0.03-0.04 mg/kg 2
- Use with caution due to risk of increased myocardial oxygen demand 1