Which toxidrome is characterized by dry, hot, dilated pupils?

• A. Sympathomimetic
• B. Opioid Toxidrome
• C. Cholinergic Toxidrome
• D. Anticholinergic Toxidrome

Answer: (D)

Toxidromes come from how different toxins disrupt autonomic signaling. When muscarinic receptors are blocked by anticholinergic agents (like some drugs or plant toxins), parasympathetic effects are suppressed. That leads to dry skin and mucous membranes because sweat glands aren’t stimulated, and heat builds up since you can’t dissipate it effectively. The pupils dilate because the muscarinic control of the iris sphincter is lost, so the radial (sympathetic) muscle dominates, producing mydriasis.

So the combination of dry, hot skin and dilated pupils is a hallmark of anticholinergic toxidrome. Other toxidromes don’t fit this pattern: for example, sympathomimetics can cause dilated pupils and hyperthermia but usually with sweaty skin; cholinergic toxicity causes sweating and secretions with constricted pupils; opioids cause pinpoint pupils and decreased mental status. This set of features—dry skin with hyperthermia and mydriasis—points to anticholinergic toxicity.