Atropine Dosing Guidelines for Organophosphate Poisoning
Initial Dosing
For adults with organophosphate poisoning, administer atropine 1-2 mg IV immediately, doubling the dose every 5 minutes until bronchorrhea, bronchospasm, and bradycardia resolve. 1, 2
For pediatric patients, the initial dose is 0.02 mg/kg IV/IO (minimum 0.1 mg, maximum single dose 0.5 mg), with higher doses required than standard pediatric resuscitation protocols. 2
The FDA-approved labeling specifies an initial single dose of 2-3 mg for adults as an antidote for organophosphorus poisoning, repeated every 20-30 minutes as needed. 3
Dose Escalation Protocol
Double the atropine dose every 5 minutes until achieving full atropinization, defined by resolution of life-threatening muscarinic symptoms. 1, 2 This aggressive escalation approach is critical—the 2023 American Heart Association guidelines emphasize that initial doses must be higher than those used for typical bradycardia. 2
The therapeutic endpoint is control of:
Clinical research supports this aggressive approach: one study documented successful use of up to 100 mg IV bolus on admission and 100 mg/hour during follow-up, with total doses reaching 11.6 grams over 12 days. 4
Maintenance Infusion
Once atropinization is achieved, maintain with a continuous infusion at 10-20% of the total loading dose per hour, up to 2 mg/hour for adults. 1 For pediatric patients, use 10-20 mg/kg/hour. 2
A randomized clinical trial demonstrated that rapid incremental dosing followed by continuous infusion significantly reduced mortality (8% vs 22.5%) compared to conventional bolus-only regimens, while also reducing time to atropinization (23.9 minutes vs 151.7 minutes). 5
Critical Therapeutic Endpoints
Monitor for signs of adequate atropinization:
- Dry lungs on auscultation
- Adequate oxygenation
- Dry skin and mucous membranes
- Mydriasis (pupil dilation) 2
Do NOT stop atropine administration due to tachycardia—this is an expected pharmacologic effect and not a contraindication to continued therapy. 2 The tachycardia may actually result from nicotinic receptor overstimulation by the organophosphate itself rather than from atropine. 2
Essential Concurrent Therapies
Always administer pralidoxime concurrently with atropine (Class 2a recommendation, Level A evidence), as atropine alone is insufficient to manage respiratory depression and nicotinic effects. 2 The American Heart Association recommends pralidoxime 1-2 g IV initially for adults, followed by 400-600 mg/hour maintenance infusion (10-20 mg/kg/hour for children). 2
Administer benzodiazepines (diazepam or midazolam) for seizures and agitation. 2
Common Pitfalls to Avoid
Never withhold atropine due to fever—repeated high-dose atropine can cause central nervous system effects including fever and hallucinations, but inadequate atropinization leads to respiratory failure and death. 2 The risk of undertreating organophosphate poisoning far exceeds the risk of atropine-induced adverse effects. 2
Avoid neuromuscular blockers metabolized by cholinesterase (succinylcholine and mivacurium) as they are contraindicated in organophosphate poisoning. 2
Do not delay antidote administration—atropine and pralidoxime must be given immediately as time-critical interventions. 2
Monitoring Requirements
Perform continuous cardiac monitoring for dysrhythmias throughout treatment. 2
Conduct serial respiratory assessments to auscultate for bronchorrhea resolution. 2
Ensure adequate personal protective equipment when caring for these patients to prevent contamination of healthcare providers. 2