Atropine 100 mg Is a Toxic Dose
100 mg of atropine is a toxic dose that can cause severe anticholinergic toxicity and potentially death. 1
Therapeutic vs. Toxic Dosing of Atropine
- Standard therapeutic doses of atropine for bradycardia in adults range from 0.5-1.0 mg IV, repeated every 3-5 minutes to a maximum total dose of 3 mg 1, 2
- Even in severe cases of organophosphate poisoning (which requires much higher atropine doses), the maximum reported therapeutic dose was 50 mg in a 24-hour period 1
- In one documented case of organophosphate poisoning requiring extremely high doses, the maximum rate was 100 mg/hour with a total dose of 11.6 g over 12 days - but this represents an extreme outlier under intensive care monitoring 3
Signs and Symptoms of Atropine Toxicity
- Initial anticholinergic effects include dry mouth, blurred vision, photophobia, tachycardia, and anhidrosis 4
- Moderate toxicity presents with restlessness, tremor, delirium, and hallucinations 4
- Severe toxicity (as would be expected with 100 mg) can lead to:
Management of Atropine Toxicity
- Physostigmine is the specific antidote for severe anticholinergic toxicity 5
- In one reported case, sequential doses of physostigmine totaling 14 mg successfully reversed toxicity from 150 mg of atropine 5
- Supportive care including:
Special Considerations
- The lethal dose of atropine is not precisely established, but 100 mg far exceeds therapeutic dosing ranges 1, 4
- Atropine toxicity can be managed successfully with intensive supportive care and physostigmine, but requires prompt recognition and treatment 5, 6
- In cases of severe anticholinergic poisoning, early administration of physostigmine may prevent the need for intubation 5
Conclusion
A 100 mg dose of atropine is approximately 33-100 times the maximum recommended therapeutic dose for bradycardia (1-3 mg) and would be considered a significant toxic ingestion requiring immediate medical intervention 1, 2, 4.