Atropine Dosing in Cardiac Arrest

Specific Dosing by Clinical Context

The American College of Cardiology recommends an initial dose of 1 mg IV atropine for bradyasystolic cardiac arrest, repeated every 3-5 minutes if asystole persists, up to a maximum total dose of 2.5 mg over 2.5 hours 1
For symptomatic bradycardia without cardiac arrest, the American College of Cardiology recommends an initial dose of 0.5-1 mg IV atropine, repeated every 3-5 minutes as needed, with a maximum total dose of 3 mg 2, 3
The American Heart Association suggests that for bradycardia without cardiac arrest, the recommended dose is 0.5 mg IV repeated every 5 minutes to a total of no more than 2 mg 1

The American College of Cardiology advises never to administer atropine doses less than 0.5 mg in adults, as this can cause paradoxical bradycardia 1, 2, 3
Atropine may be ineffective or harmful in patients with type II second-degree or third-degree AV block with wide QRS complex, as the block occurs in non-nodal tissue 4
Heart transplant patients may experience paradoxical high-degree AV block or sinus arrest with atropine due to lack of parasympathetic reinnervation 2, 3, 4

The American College of Cardiology recommends confirming asystole in at least two ECG leads before administering atropine 1
The American Heart Association suggests administering atropine 1 mg IV immediately for bradyasystolic cardiac arrest, with peak effect within 3 minutes 1
If asystole persists after 3-5 minutes, the American College of Cardiology recommends repeating 1 mg IV atropine, not exceeding 2.5 mg total dose over 2.5 hours 1

The American College of Cardiology warns of potential adverse effects, including sinus tachycardia, which may worsen ischemia, and ventricular tachycardia or fibrillation, which are rare but reported 1
Central anticholinergic syndrome can occur with excessive doses (>3 mg) of atropine, causing confusion, hallucinations, and fever 1, 4
Paradoxical bradycardia can occur with doses less than 0.5 mg of atropine 1, 2, 3