Atropine & Anticholinergic Overdose

Key Features

• Antimuscarinic agents with variable CNS effects

  • Atropine

  • Scopolamine

  • Belladonna

  • Datura stramonium

  • Hyoscyamus niger

  • Some mushrooms

  • Tricyclic antidepressants

  • Antihistamines

Clinical Findings

• Anticholinergic syndrome

  • Dryness of the mouth, thirst, difficulty swallowing, blurring of vision

  • Dilated pupils, flushed skin, tachycardia, fever, delirium, myoclonus, ileus

• Antidepressants and antihistamines may induce convulsions

• Diphenhydramine commonly causes delirium, tachycardia, and seizures; massive overdose may mimic tricyclic antidepressant cardiotoxic poisoning

• Terfenadine and astemizole cause QT interval prolongation and torsades de pointes and were removed from US market

Diagnosis

• Based on history of ingestion, typical "anticholinergic syndrome"

• Serum levels not useful

• ECG monitoring for wide QRS, QT prolongation

Treatment

Emergency and supportive measures

• Activated charcoal

  • Administer 60–100 g mixed in aqueous slurry orally or via gastric tube

  • Do not use for comatose or convulsing patients unless they are intubated with a cuffed endotracheal tube

• External cooling and sedation, or neuromuscular paralysis in rare cases, are indicated to control high temperatures

Specific treatment

• For severe anticholinergic syndrome, (eg, agitated delirium),

  • Give physostigmine salicylate, 0.5–1 mg intravenously slowly over 5 minutes, with ECG monitoring

  • Repeat as needed to total dose of no more than 2 mg

• Caution: Bradyarrhythmias and convulsions are a hazard with physostigmine administration, and the drug should not be used in patients with evidence of cardiotoxic effects (eg, QRS interval prolongation) from tricyclic antidepressants or other sodium channel blockers