From the Guidelines
Atropine is recommended for symptomatic bradycardia at a dose of 0.5 mg IV bolus, which can be repeated every 3-5 minutes up to a maximum total dose of 3 mg, as supported by the 2010 American Heart Association guidelines 1. For organophosphate poisoning, much higher doses are required: initially 1-2 mg IV, followed by doubling doses every 5 minutes until muscarinic symptoms improve, often requiring 20-50 mg or more in severe cases, as indicated in the 2023 American Heart Association focused update 1. In bradycardia, atropine works by blocking parasympathetic (vagal) influence on the heart, increasing heart rate and conduction through the AV node. For organophosphate poisoning, atropine counteracts acetylcholine accumulation by blocking muscarinic receptors, addressing respiratory secretions, bronchospasm, and bradycardia, but does not affect nicotinic symptoms like muscle weakness. Pediatric dosing for bradycardia is 0.01-0.02 mg/kg with a minimum single dose of 0.1 mg and maximum of 0.5 mg, repeatable to a maximum total of 1 mg in children and 2 mg in adolescents, as stated in the 2008 Pediatrics article 1. Atropine should be administered rapidly as slow administration or doses below 0.5 mg may paradoxically worsen bradycardia. Key considerations include:
- Monitoring for signs of atropinization, such as dry secretions and pupil dilation, to guide dosing in organophosphate poisoning
- Avoiding delays in implementing external pacing for patients with poor perfusion
- Using caution in the presence of acute coronary ischemia or MI, as increased heart rate may worsen ischemia or increase infarction size
- Considering the potential need for large doses of atropine in anticholinesterase or nerve gas poisonings, along with the addition of pralidoxime. The most recent and highest quality study, the 2023 American Heart Association focused update 1, provides the basis for these recommendations, prioritizing morbidity, mortality, and quality of life outcomes.
From the FDA Drug Label
ATROPINE SULFATE INJECTION, for intravenous use ... DOSAGE AND ADMINISTRATION For intravenous administration. ( 2). Titrate according to heart rate, PR interval, blood pressure and symptoms. ( 2) Adult dosage Antisialagogue or for antivagal effects: Initial single dose of 0. 5 to 1 mg. ( 2) Antidote for organophosphorus or muscarinic mushroom poisoning: Initial single dose of 2 to 3 mg, repeated every 20 to 30 minutes. ( 2) Bradyasystolic cardiac arrest: 1 mg dose, repeated every 3 to 5 minutes if asystole persists. ( 2)
The recommended dosage and administration of atropine in clinical scenarios such as symptomatic bradycardia and organophosphate poisoning are as follows:
- Symptomatic Bradycardia: The label does not explicitly mention the dosage for symptomatic bradycardia, but it does mention Antisialagogue or for antivagal effects: Initial single dose of 0.5 to 1 mg.
- Organophosphate Poisoning: Initial single dose of 2 to 3 mg, repeated every 20 to 30 minutes 2. Key Considerations:
- Titrate according to heart rate, PR interval, blood pressure, and symptoms.
- Patients with Coronary Artery Disease: Limit the total dose to 0.03 mg/kg to 0.04 mg/kg.
From the Research
Atropine Dosage and Administration
The recommended dosage and administration of atropine vary depending on the clinical scenario.
- For symptomatic bradycardia, atropine is administered systemically, but the exact dosage is not specified in the provided studies 3.
- For organophosphate poisoning, high-dose atropine therapy is recommended, with the highest dose given being 100 mg intravenously on admission and 100 mg/h/day during follow-up, with a total dose of 11.6 g/12 days 4.
- Atropine can be administered until secretions disappear, and intensive care should be exerted in the follow-up of these patients 4.
Clinical Scenarios
- In cases of organophosphate poisoning, atropine is essential in treating muscarinic symptoms, and its administration can help reverse the effects of the poisoning 4, 5.
- Atropine has beneficial effects on the heart rate, prolongs the time before the heart rate declines, and delays death in cases of organophosphate poisoning 6.
- Cardiac abnormalities, including QT interval prolongation, ST-T changes, and ventricular premature contractions, can occur in patients with acute organophosphate poisoning, and continuous cardiac monitoring is recommended 7.