STEPTRACKERPHARMACOLOGY + TOXICOLOGY | TOXICOLOGY | HIGH-YIELD REVIEW

Toxidromes & Antidotes

Most poisonings can be sorted from vital signs, pupils, skin and bowel sounds into a handful of toxidromes — and many have a specific antidote worth knowing cold.

FOCUS ON
Sympathomimetic (cocaine, amphetamines): ↑ HR, BP, temp, mydriasis, diaphoresis, agitation → benzodiazepines. Anticholinergic (antihistamines, TCAs, atropine, jimsonweed): same vitals, mydriasis, dry flushed skin, ↓ bowel sounds, retention, delirium → physostigmine (not in TCA). Cholinergic (organophosphates, nerve agents): miosis, secretions, bronchorrhea, bradycardia, fasciculations → atropine + pralidoxime. Opioid: miosis, ↓ RR, coma → naloxone. Sedative-hypnotic: sedation, normal pupils, ↓ RR (mild) → supportive (flumazenil rarely). Serotonin syndrome → cyproheptadine. Decontamination: activated charcoal within ~1–2 h (not for metals, lithium, alcohols, hydrocarbons, caustics); whole-bowel irrigation (iron, lithium, packets); hemodialysis for toxic alcohols, lithium, salicylates, metformin, valproate, theophylline. Anion-gap acidosis poisons: methanol, ethylene glycol, salicylates, iron, isoniazid, CO/cyanide (lactate), metformin. Osmolar gap: toxic alcohols.
POISON
KEY FEATURES
ANTIDOTE / TREATMENT
NOTES
Acetaminophen
Nausea, then ↑ AST/ALT day 2–3, liver failure
N-acetylcysteine
4-h level on nomogram
Salicylates
Tinnitus, respiratory alkalosis + AG acidosis, fever
Sodium bicarbonate; dialysis
Avoid intubation if possible (worsens acidosis)
Opioids
Miosis, bradypnea, coma
Naloxone
Redose for long-acting agents
Benzodiazepines
Sedation, normal vitals mostly
Supportive; flumazenil only if not dependent
Flumazenil → seizures
TCAs
Anticholinergic signs, wide QRS, seizures, hypotension
Sodium bicarbonate
Avoid physostigmine, class IA/IC drugs
Organophosphates
Muscarinic + nicotinic excess
Atropine + pralidoxime
Decontaminate skin, protect staff
Anticholinergics
Hot, dry, flushed, delirious, mydriasis, retention
Physostigmine
Benzodiazepines for agitation
β-blockers · Ca²⁺ channel blockers
Bradycardia, hypotension; CCB → hyperglycemia, β-blocker → hypoglycemia
Glucagon (β-blocker), IV calcium, high-dose insulin + glucose, lipid emulsion
Pressors, pacing
Digoxin
Vomiting, yellow vision, arrhythmias, hyperkalemia
Digoxin immune Fab
Correct Mg²⁺; avoid calcium (debated)
Methanol · ethylene glycol
AG acidosis + osmolar gap; vision loss · oxalate crystals, AKI
Fomepizole (or ethanol); dialysis
Folate (methanol), thiamine + B6 (ethylene glycol)
Iron
GI bleeding, then shock, acidosis, liver failure
Deferoxamine
Radiopaque pills; charcoal useless
Isoniazid
Refractory seizures, AG acidosis
Pyridoxine (B6)
—
Heparin · warfarin · DOACs
Bleeding
Protamine · vitamin K + PCC · idarucizumab, andexanet
—
Sulfonylureas
Recurrent hypoglycemia
Dextrose + octreotide
Observe 24 h

Mechanism — toxic alcohol metabolism

Methanol · ethylene glycol
→
Alcohol dehydrogenaseFomepizole, ethanol block
→
Formic acid · glycolic + oxalic acid
→
Blindness · kidney failure

Toxidrome grid

TOXIDROME
PUPILS
SKIN
BOWEL
Sympathomimetic
Big
Sweaty
Normal
Anticholinergic
Big
Dry
↓
Cholinergic
Small
Sweaty
↑
Opioid
Small
Normal
↓

How it's tested

COMMON CONFUSIONSympathomimetic and anticholinergic poisonings both cause tachycardia, hypertension, hyperthermia and dilated pupils — check the skin and bowel sounds.
THE TRAPActivated charcoal doesn't bind iron, lithium, alcohols, metals, acids or alkalis — choose whole-bowel irrigation or dialysis instead.
YOUR APPROACHABCs → glucose → toxidrome from vitals/pupils/skin → ECG, AG and osmolar gap, levels → antidote → decontaminate/eliminate.

If you see… think…

Visual blurring "snowfield" and AG acidosis after homemade liquor → methanol → fomepizole
Calcium oxalate crystals, AKI, AG acidosis → ethylene glycol
Seizures not stopping with lorazepam, TB patient → isoniazid → pyridoxine
Bradycardia, hypotension, hyperglycemia → calcium channel blocker overdose
Bradycardia, hypotension, hypoglycemia → β-blocker overdose → glucagon
Wide QRS after antidepressant overdose → sodium bicarbonate
Recurrent hypoglycemia after a diabetes pill overdose → octreotide
Radiopaque tablets on abdominal X-ray, child → iron
Hyperkalemia with digoxin toxicity → digoxin Fab
Agitated, sweaty, hyperthermic, dilated pupils → sympathomimetic → benzodiazepines