What is the recommended atropine dosage for treating organophosphate poisoning?

Atropine Dosing for Organophosphate Poisoning

For organophosphate poisoning, the recommended initial atropine dosage is 1-2 mg IV, doubled every 5 minutes until reversal of cholinergic symptoms, followed by a maintenance infusion of 10-20% of the total loading dose per hour (up to 2 mg/h). 1, 2

Initial Dosing Protocol

• Adults:

  • Initial dose: 1-2 mg IV 1
  • Double the dose every 5 minutes until achieving atropinization 1
  • FDA label indicates 2-3 mg initially, repeated every 20-30 minutes 3

• Children:

  • Initial dose: 0.02 mg/kg 2
  • Double the dose every 5 minutes 2

Clinical Endpoints for Atropinization

Titrate atropine administration until reversal of:

• Bronchorrhea (excessive secretions)
• Bronchospasm
• Bradycardia
• Hypotension 2

Maintenance Dosing

After achieving atropinization:

• Maintenance infusion: 10-20% of the total loading dose per hour
• Maximum maintenance rate: 2 mg/hour in adults 2, 1
• Continue until cholinesterase activity normalizes 1

Important Clinical Considerations

• High doses may be required: Some severe cases have required up to 100 mg/hour and total doses as high as 11.6 grams over 12 days 4
• Rapid atropinization is crucial: Modern protocols emphasize faster atropinization compared to older regimens 5
• Continuous monitoring: Assess heart rate, secretions, pupil size, and lung sounds frequently to guide dosing
• Duration of therapy: Treatment typically continues for several days (mean 9.6 days in one study) 6

Potential Challenges

• Atropine resistance: In some cases, atropinization cannot be achieved despite high doses. Alternative antimuscarinic agents like anisodamine may be considered in these situations 7
• Adverse effects: Watch for antimuscarinic side effects including tachycardia, blurred vision, urinary retention, and confusion 3

Comprehensive Management

• Atropine should be administered alongside:
  • Pralidoxime (2-PAM): 1-2 grams IV over 15-30 minutes initially, followed by 400-600 mg/hour maintenance 1
  • Proper decontamination procedures
  • Respiratory support as needed (many severe cases require mechanical ventilation) 8

Remember that aggressive atropinization is a cornerstone of therapy in organophosphate poisoning, with evidence suggesting improved outcomes when administered promptly and in sufficient doses 8, 4.