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Clinical findings include hypotension or hypertension, tachycardia, hypoactive or absent bowel sounds, urinary retention, flushed skin, hyperthermia, dry skin and mucus membranes, mydriasis, confusion, agitation, disorientation, and auditory and visual hallucinations. Table 101-1 compares muscarinic and antimuscarinic effects.

Table 101-1

Muscarinic and Antimuscarinic Effects


The diagnosis is primarily clinical. In isolated anticholinergic toxicity, routine laboratory studies should be normal, and routine toxicology screening is often of little value. Nonetheless, check electrolytes, glucose, and creatine phosphokinase levels. The differential diagnosis includes viral encephalitis, Reye syndrome, head trauma, other intoxications, neuroleptic malignant syndrome, delirium tremens, acute psychiatric disorders, and sympathomimetic toxicity.


Treatment is primarily supportive. The goal is to prevent life-threatening complications, which include status epilepticus, hyperthermia, cardiovascular collapse, and rhabdomyolysis.

  1. Place the patient on a cardiac monitor and secure intravenous or intraosseous access.

  2. Activated charcoal may decrease drug absorption, even beyond 1 hour of ingestion.

  3. Monitor temperature. Treat hyperthermia using conventional methods.

  4. Hypertension usually does not require intervention, but should be treated conventionally as necessary.

  5. Standard antidysrhythmics are usually effective, but avoid class IA medications (e.g., procainamide). Treat dysrhythmias, widened QRS complexes, and hypotension from sodium blocking agents (e.g., cyclic antidepressants) with IV sodium bicarbonate 1 mEq/kg.

  6. Treat agitation with benzodiazepines, such as lorazepam 2 to 4 mg IV or 0.1 mg/kg). Avoid use of phenothiazines.

  7. Treat seizures with benzodiazepines, such as lorazepam 2 mg IV or 0.1 mg/kg.

  8. Physostigmine treatment is controversial. It is indicated if conventional therapy fails to control seizures, severe agitation, unstable dysrhythmias, coma with respiratory depression, malignant hypertension, or hypotension. The initial dose is 0.5 to 2 mg IV (0.02 mg/kg in children, maximum dose 2 mg), slowly administered over 5 minutes. When effective, a significant decrease in agitation may be apparent within 15 to 20 minutes. Physostigmine may worsen cyclic antidepressant toxicity and lead to bradycardia and asystole. It is contraindicated in patients with cardiovascular or peripheral vascular disease, bronchospasm, intestinal or bladder obstruction, cardiac conduction disturbances, and suspected concomitant sodium channel antagonist ...

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