Atropine & Anticholinergic Overdose

KEY FEATURES

• Antimuscarinic agents with variable central nervous system effects

  • Atropine

  • Scopolamine

  • Belladonna

  • Datura stramonium

  • Hyoscyamus niger

  • Some mushrooms

  • Tricyclic antidepressants

  • Antihistamines

CLINICAL FINDINGS

• Anticholinergic syndrome

  • Symptoms of toxicity

    • Dryness of the mouth

    • Thirst

    • Difficulty swallowing

    • Blurring of vision

  • Physical signs

    • 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

DIAGNOSIS

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

• Serum levels not useful

• ECG monitoring for wide QRS, QT prolongation

TREATMENT

• Activated charcoal

  • Administer 50–100 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

• 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