Toxicologic Disorders
Core approach
Toxicology questions reward pattern recognition and physiologic reasoning. Learn toxidromes: opioid, sympathomimetic, anticholinergic, cholinergic, sedative-hypnotic, and serotonin syndrome. Know key antidotes: naloxone, N-acetylcysteine, sodium bicarbonate for salicylate or sodium-channel blockade, calcium for hydrofluoric acid or calcium-channel blocker toxicity, glucagon, lipid emulsion, hydroxocobalamin, methylene blue, and fomepizole. Obtain targeted labs, ECG, and acetaminophen/salicylate levels when indicated. Decontamination is selective; activated charcoal has narrow indications and contraindications.
Traps
Mixed ingestions are common; do not stop at one toxidrome. Delayed toxicity occurs with acetaminophen, salicylates, and sustained-release preparations. Naloxone's duration may be shorter than the opioid, requiring infusion or observation. Flumazenil can precipitate seizures in benzodiazepine-tolerant patients. A normal anion gap does not exclude toxic ingestion, and an osmolar gap is insensitive. Do not use gastric lavage routinely.
Worked example
A patient presents after an intentional overdose. Acetaminophen level is drawn at four hours and plotted on the Rumack-Matthew nomogram. If the level is above the treatment line or timing is uncertain, start N-acetylcysteine. Rule of thumb: treat suspected acetaminophen toxicity early; waiting for liver enzymes delays the window for protection.
Key concepts
Sodium bicarbonate is used for salicylate toxicity and wide-complex sodium-channel blocker toxicity. Serotonin syndrome causes clonus, hyperreflexia, and agitation; stop serotonergic drugs and use benzodiazepines.