Atropine Dosing for Organophosphate Poisoning
For organophosphate poisoning, administer an initial atropine dose of 1-2 mg IV for adults (0.02 mg/kg for children, minimum 0.1 mg, maximum single dose 0.5 mg in pediatrics), then double the dose every 5 minutes until full atropinization is achieved. 1
Initial Dosing Algorithm
Adult patients:
- Start with 1-2 mg IV immediately upon recognition of severe poisoning manifestations (bronchospasm, bronchorrhea, seizures, or significant bradycardia) 1, 2, 3
- This is substantially higher than the 0.5-1.0 mg used for bradycardia from other causes 1
Pediatric patients:
- Initial dose: 0.02 mg/kg IV/IO 1, 2
- Minimum dose: 0.1 mg 2
- Maximum single dose: 0.5 mg 2
- Higher doses than standard pediatric resuscitation are required—do not underdose 2
Dose Escalation Protocol
The key principle is aggressive, rapid escalation:
- Double the previous dose every 5 minutes until atropinization endpoints are reached 1, 2, 3
- This doubling strategy is critical and differs from fixed-dose repetition 1
- Continue escalation regardless of heart rate—tachycardia is NOT a contraindication to continued dosing 2, 3
Endpoints of Atropinization
Stop escalating when ALL of the following are achieved:
- Clear chest on auscultation (resolution of bronchorrhea) 3
- Heart rate >80 beats/min 3
- Systolic blood pressure >80 mm Hg 3
- Dry skin and mucous membranes 1, 3
- Mydriasis (pupil dilation) 1, 3
Maintenance Therapy
After achieving initial atropinization:
- Administer 10-20% of the total loading dose per hour, up to 2 mg/h in adults 1
- Continuous infusion is preferred over intermittent boluses for maintenance 2, 3
- Monitor closely for at least 48-72 hours as delayed complications can occur 2, 3
Critical Management Principles
Common pitfalls to avoid:
- Never delay atropine administration—it is the immediate life-saving intervention with Class 1, Level A evidence 2, 4
- Do not underdose—organophosphate poisoning often requires hundreds to thousands of mg total (case reports document up to 3000 mg) 5, 6
- Do not stop escalation due to tachycardia—the therapeutic endpoint is control of muscarinic symptoms, not heart rate normalization 2, 3
- Tachycardia may originate from nicotinic receptor overstimulation by the organophosphate itself, not from atropine 2, 3
Essential concurrent therapies:
- Always administer pralidoxime (1-2 g IV initially, then 400-600 mg/hour maintenance) as it reverses nicotinic effects that atropine cannot address 2, 3
- Give benzodiazepines (diazepam or midazolam) for seizures and agitation 2, 3, 4
- Perform early endotracheal intubation for life-threatening poisoning, avoiding succinylcholine and mivacurium 2, 3, 4
Evidence Quality Note
The 2023 American Heart Association guidelines provide the highest quality evidence, giving atropine a Class 1 recommendation with Level A evidence for severe organophosphate poisoning 2. Research studies support that rapid incremental dosing with infusion reduces mortality compared to conventional fixed bolus dosing (8% vs 22.5% mortality, p<0.05) 7. The FDA label confirms 2-3 mg initial dosing for organophosphate poisoning, repeated every 20-30 minutes 8.