Antimuscarinic toxidrome vs Sympathomimetic toxidrome
How to tell Antimuscarinic toxidrome and Sympathomimetic toxidrome apart when a board question makes them look alike.
Antimuscarinic: dry skin with quiet bowel sounds; sympathomimetic: diaphoretic skin with preserved or hyperactive bowel sounds.
Side by side
Agitation, mydriasis, hot dry skin, urinary retention, and decreased bowel sounds.
Agitation, mydriasis, hypertension, tachycardia, diaphoresis, hyperreflexia, and catecholamine-driven hyperthermia.
Muscarinic receptor blockade removes parasympathetic secretions and bladder/bowel activity.
Catecholamine excess overstimulates alpha and beta adrenergic receptors.
Dry skin and urinary retention point antimuscarinic.
Diaphoresis with adrenergic excess points toward sympathomimetic toxicity.
The trap
Mydriasis, tachycardia, hypertension, agitation, and hyperthermia occur in both, so adrenergic-looking vital signs do not pick the toxidrome. The deciding bedside features are skin (DRY in antimuscarinic, DIAPHORETIC in sympathomimetic) and bowel sounds (decreased with ileus in antimuscarinic, preserved or hyperactive in sympathomimetic). Anticholinergic delirium responds to physostigmine; sympathomimetic agitation responds to benzodiazepines, and antipsychotics should be avoided because they further impair heat dissipation.
Watch it explained
The repair move
In toxidromes, skin moisture and bladder/bowel findings are the fastest separators.
Try a free question
CoreAn agitated patient has dilated pupils, fever, flushed dry skin, urinary retention, and absent bowel sounds. Which toxidrome is most likely?
Show answer and explanation
Answer: A. Antimuscarinic toxidrome. Dry skin, urinary retention, and decreased bowel sounds point to antimuscarinic toxicity.
Why the other choices are tempting
- B. Sympathomimetic toxicity is typically sweaty from catecholamine excess.
- C. Opioid intoxication causes miosis and respiratory depression.
- D. Cholinergic toxicity causes salivation, lacrimation, urination, diarrhea, and bronchorrhea.
- E. Sedative-hypnotic intoxication causes CNS depression.
Flashcards
Tap a card to flip it.
What is the fastest separator for Antimuscarinic toxidrome vs Sympathomimetic toxidrome?
Antimuscarinic: dry skin with quiet bowel sounds; sympathomimetic: diaphoretic skin with preserved or hyperactive bowel sounds.
What clue should make you choose Antimuscarinic toxidrome?
Agitation, mydriasis, hot dry skin, urinary retention, and decreased bowel sounds.
Quick answers
What is the fastest way to tell Antimuscarinic toxidrome from Sympathomimetic toxidrome?
Antimuscarinic: dry skin with quiet bowel sounds; sympathomimetic: diaphoretic skin with preserved or hyperactive bowel sounds.
What is the key clue for Antimuscarinic toxidrome?
Agitation, mydriasis, hot dry skin, urinary retention, and decreased bowel sounds.
What is the key clue for Sympathomimetic toxidrome?
Agitation, mydriasis, hypertension, tachycardia, diaphoresis, hyperreflexia, and catecholamine-driven hyperthermia.
What is the common trap with Antimuscarinic toxidrome vs Sympathomimetic toxidrome?
Mydriasis, tachycardia, hypertension, agitation, and hyperthermia occur in both, so adrenergic-looking vital signs do not pick the toxidrome. The deciding bedside features are skin (DRY in antimuscarinic, DIAPHORETIC in sympathomimetic) and bowel sounds (decreased with ileus in antimuscarinic, preserved or hyperactive in sympathomimetic). Anticholinergic delirium responds to physostigmine; sympathomimetic agitation responds to benzodiazepines, and antipsychotics should be avoided because they further impair heat dissipation.