Toxicology, Pharmacology, and Environmental Emergencies
Core concepts
Know the classic toxidromes: opioid (miosis, respiratory depression), sympathomimetic, anticholinergic, cholinergic, and sedative-hypnotic. Master antidotes: naloxone for opioids, flumazenil for benzodiazepines (cautiously), N-acetylcysteine for acetaminophen, sodium bicarbonate for salicylates and tricyclics, fomepizole for toxic alcohols, and hydroxocobalamin for cyanide. Understand gastrointestinal decontamination limits and the role of hemodialysis for dialyzable toxins. Recognize environmental emergencies: heat stroke, hypothermia, carbon monoxide poisoning, and envenomations.
Traps
Flumazenil can precipitate seizures in mixed overdose or chronic benzodiazepine use - use cautiously. Acetaminophen toxicity is time-dependent; the Rumack-Matthew nomogram guides N-acetylcysteine. In carbon monoxide poisoning, pulse oximetry is falsely normal; use co-oximetry. In salicylate toxicity, urinary alkalinization enhances elimination. Do not give activated charcoal to a patient with altered mental status or unprotected airway.
Worked example
A patient presents with an anion-gap metabolic acidosis, visual disturbance, and a history of ingesting an unknown liquid. This suggests methanol poisoning. Treat with fomepizole (or ethanol if unavailable), sodium bicarbonate for acidosis, and hemodialysis for severe cases. Rule of thumb: toxic alcohols cause an osmolal gap early and an anion gap later.