Toxicology: Toxidromes & Critical Antidotes

Resuscitation Quick Ribbon (First 2 Minutes)

N-acetylcysteine (NAC):150 mg/kg IV over 1h, then 50 mg/kg over 4h, then 100 mg/kg over 16h (or oral 140 mg/kg load)

Naloxone:0.04–0.4 mg IV (titrate for respiratory depression in opioid overdose)

Fomepizole:15 mg/kg IV loading dose over 30 min (inhibits alcohol dehydrogenase for methanol/ethylene glycol)

Sodium Bicarbonate:1–2 mEq/kg IV push for QRS > 100 ms in TCA overdose; alkalinize urine to pH 7.5–8.0 in ASA

High-Dose Insulin (HIET):1 unit/kg IV bolus + 1 unit/kg/h infusion + D50W for severe calcium channel / beta-blocker toxicity

Bottom-Line Clinical Pearl

In unknown overdose cases, physical examination reveals the toxidrome (vitals, pupils, skin moisture, bowel sounds, reflex tone). Always obtain an Acetaminophen level, Aspirin level, ECG, and blood glucose. For Acetaminophen poisoning, use the Rumack-Matthew nomogram starting at 4 hours post-ingestion; N-acetylcysteine (NAC) is 100% hepatoprotective if started within 8 hours. Toxic alcohols (methanol, ethylene glycol) present with high anion gap metabolic acidosis and elevated osmolar gap (> 10); treat with Fomepizole and urgent hemodialysis.

1. The 5 Major Toxidromes Physical Exam Signature

Toxidrome	Heart Rate / BP	Pupils	Skin / Moisture	Bowel Sounds	Key Features & Antidote
Anticholinergic	Tachycardia / Hypertension	Mydriasis (Dilated)	Dry, flushed, hot	Decreased / Absent	Delirium, urinary retention ('blind as bat, mad as hatter'); Physostigmine
Cholinergic	Bradycardia / Variable	Miosis (Constricted)	Profoundly Diaphoretic	Hyperactive	SLUDGEM (salivation, lacrimation, urination, defecation, GI upset, emesis); Atropine + Pralidoxime
Sympathomimetic	Tachycardia / Severe HTN	Mydriasis (Dilated)	Diaphoretic / Sweaty	Normal / Increased	Hyperthermia, agitation, seizures (Cocaine, Meth); Benzodiazepines first-line
Opioid	Bradycardia / Hypotension	Miosis (Pinpoint)	Dry / Normal	Decreased	Hypoventilation (RR < 8–10/min), CNS depression; Naloxone
Sedative-Hypnotic	Normal / Slight Brady	Normal / Variable	Dry / Normal	Decreased	CNS depression with normal vital signs (Benzos, Barbs, Z-drugs); Supportive care