Toxicology & Substance Use · Topic 1 of 17

Poisoned Patient: Toxidromes & Approach

Toxicology · the poisoned patient

Poisoned Patient: Toxidromes & Approach

Stabilize airway, breathing and circulation first, then read the toxidrome — pupils, skin, heart rate, temperature and mental status point to the drug class.

Key numbers

Activated charcoal within 1–2 hours0.5–2 g/kg, ≤ 1–2 h

Atropine until secretions dry, then pralidoximeAtropine 2–3 mg IV, double

01 · Look forAnticholinergic: hot, dry, flushed, delirious

Anticholinergic toxidrome: tachycardia, hyperthermia, mydriasis, warm dry flushed skin, urinary retention, ileus and delirium — from antihistamines (diphenhydramine), tricyclics, scopolamine, atropine or jimson weed.

02 · Look forCholinergic: secretions, miosis, bradycardia, bronchorrhea

Cholinergic (muscarinic) toxidrome — organophosphates, carbamates, nerve agents: salivation, lacrimation, urination, diarrhea, emesis, miosis, bronchorrhea, bronchospasm and bradycardia; nicotinic effects add fasciculations and weakness that can paralyze respiratory muscles.

03 · Look forSympathomimetic: agitated, diaphoretic, hypertensive

Sympathomimetic toxidrome — cocaine, amphetamines, MDMA, cathinones: tachycardia, hypertension, mydriasis, agitation, diaphoresis, hyperthermia and seizures; benzodiazepines are first-line for agitation.

Presentation

What you'll see

Opioid: hypoventilation, miosis, sedation must knowOpioid toxidrome: decreased respiratory rate and depth, miosis, sedation to coma, sometimes hypotension and hypothermia — ventilate and give naloxone (see Opioid Overdose).

Sedative-hypnotic: CNS depression, near-normal vital signsSedative-hypnotic toxidrome (benzodiazepines, barbiturates, ethanol, Z-drugs): somnolence to coma, slurred speech and ataxia with normal or decreased vital signs and variable pupils — treat with airway and ventilatory support.

Do right now

In this order

First moves

Airway, breathing, circulation before any antidote

→

Call the poison center: 1-800-222-1222

→

Acetaminophen level in every intentional ingestion

→

Activated charcoal within 1–2 hours0.5–2 g/kg, ≤ 1–2 h

Why each step

Airway, breathing, circulation before any antidoteStabilize first: secure airway and ventilation, give IV naloxone for apnea or severe respiratory depression, check bedside glucose (thiamine 100 mg IV with dextrose in at-risk adults), and treat hypotension with fluids, then vasopressors.

Call the poison center: 1-800-222-1222Consult the poison center (US 1-800-222-1222, which connects to toxicologists) for all but the mildest poisonings; product labels may list outdated first aid and antidotes.

Acetaminophen level in every intentional ingestionOrder an acetaminophen level in every intentional or mixed ingestion (common, silent early, treatable), plus ECG, glucose, electrolytes, renal function and a blood gas when mental status or vital signs are abnormal.

Activated charcoal within 1–2 hoursConsider activated charcoal 0.5–2 g/kg (usually 50–100 g in adults) when a toxic ingestion presented within 1–2 hours and the airway is protected; it has not been shown to reduce mortality.

Management

Orders

Whole-bowel irrigation: sustained-release, metals, drug packetsWhole-bowel irrigation with polyethylene glycol (until rectal effluent is clear) is reserved for serious sustained-release or charcoal-unbound ingestions (iron, other metals), body packers and bezoars; gastric lavage and ipecac are no longer routine.

Atropine until secretions dry, then pralidoximeOrganophosphate poisoning: atropine 2–3 mg IV, doubled every 3–5 minutes until bronchorrhea and bronchospasm clear (not pupil size or heart rate), then pralidoxime 1–2 g IV over 15–30 minutes for neuromuscular weakness.

Dialyzable toxins: alcohols, lithium, salicylates, theophyllineToxins that may need hemodialysis are small, water-soluble and poorly protein-bound: ethylene glycol, methanol, lithium, salicylates and theophylline; drugs with a large volume of distribution (digoxin, tricyclics) are not dialyzable.

Red flags & don'ts

Avoid harm

Charcoal does not bind alcohols, metals, lithium avoidActivated charcoal is ineffective for caustics, alcohols and simple ions (iron, lithium, other metals, cyanide) and is withheld when the patient may vomit and aspirate without a protected airway.

Avoid flumazenil in undifferentiated overdose avoidAvoid flumazenil in undifferentiated coma or mixed overdose and in benzodiazepine-dependent patients: it can precipitate refractory withdrawal seizures and dysrhythmias; support ventilation instead.

Anticholinergic or sympathomimetic?

Commonly confused

Skin	Warm, dry, flushed
Pupils	Mydriasis
Heart rate and temperature	Tachycardia, hyperthermia
Gut and bladder	Ileus, urinary retention
Typical causes	Antihistamines, TCAs, scopolamine, jimson weed
Treatment	Benzodiazepines; physostigmine only with a toxicologist

Commonly confused

Tell apart

Urine drug screens miss fentanyl and methadoneStandard urine drug screens are qualitative and limited: the opioid immunoassay misses fentanyl and methadone, and a positive result does not prove the drug caused the presentation.

More detail

Reference

Show 6 reference facts

Physostigmine can reverse anticholinergic delirium but is controversial and given only with toxicologist input; benzodiazepines treat anticholinergic agitation and seizures.

Urine alkalinization (D5W with 3 ampules sodium bicarbonate plus potassium, urine pH ≥ 7.5) enhances elimination of weak acids such as salicylates and phenobarbital; it is contraindicated in renal insufficiency.

Nicotinic toxidrome (nicotine, some organophosphates, black widow bites): mydriasis, tachycardia, weakness, hypertension, hyperglycemia, fasciculations and sweating.

IV lipid emulsion and high-dose insulin have been used successfully for cardiotoxic poisonings such as bupivacaine, diltiazem and verapamil (see Beta-Blocker & Calcium Channel Blocker Overdose).

Get history from every source — EMS, family, pill bottles, pharmacy records — and assume multiple substances and suicidal intent in adult intentional ingestions; still exclude head trauma, CNS infection, hypoglycemia and Wernicke encephalopathy.

Withdrawal syndromes also form toxidromes: sedative-hypnotic withdrawal (alcohol, benzodiazepines, baclofen, GHB) causes agitation, seizures and autonomic instability; opioid withdrawal causes mydriasis, yawning, piloerection and diarrhea but is not life-threatening.

Pearl

Anticholinergic: hot as a hare, dry as a bone, red as a beet, blind as a bat, mad as a hatter — sweat separates it from sympathomimetic toxicity.

Sources · Merck Manual Professional — General Principles of Poisoning (toxidrome table, decontamination, antidotes) · Merck Manual Professional — Opioid Toxicity and Withdrawal · Dutta S et al. A Narrative Review on Toxidromes in the Psychiatric Population. J Clin Med 2025 · Chandran J, Krishna B. Initial Management of Poisoned Patient. Indian J Crit Care Med 2019 (toxidrome table) · Merck Manual Professional — Organophosphate Poisoning and Carbamate Poisoning · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).