Antidotes, Decontamination, and Enhanced Elimination
Decontamination
Activated charcoal (1 g/kg) adsorbs most drugs if given within 1–2 hours, but is contraindicated in caustic ingestion, unprotected airway, ileus, and hydrocarbon aspiration risk; it is not useful for iron, lithium, alcohols, or most metals. Gastric lavage is reserved for very early, life-threatening ingestions. Whole-bowel irrigation with polyethylene glycol helps with sustained-release products, iron, lithium, and body packers. Skin and eye decontamination should be prompt and copious.
Enhanced elimination
Urinary alkalinization works for salicylate and, with sodium bicarbonate for serum pH, for tricyclics. Hemodialysis criteria combine toxin characteristics (small size, low protein binding, small Vd, water solubility) with clinical severity: methanol, ethylene glycol, lithium, salicylate, theophylline, and toxic alcohols are classic candidates. Hemoperfusion is occasionally used for theophylline.
Antidote pairings to memorize
- Acetaminophen - N-acetylcysteine. Opioids - naloxone. Benzodiazepines - flumazenil (with caveats).
- Methanol/ethylene glycol - fomepizole or ethanol. Isoniazid seizures - pyridoxine.
- Methemoglobinemia - methylene blue, avoided in G6PD deficiency.
- Organophosphate - atropine plus pralidoxime. Cyanide - hydroxocobalamin.
- Sulfonylurea - octreotide. Beta blocker - glucagon. Digoxin - Fab.
- Iron - deferoxamine. Lead - succimer, dimercaprol, EDTA.
- Valproate hepatotoxicity - L-carnitine. Local anesthetic toxicity - lipid emulsion.
Rule of thumb: antidotes never replace airway, breathing, and circulatory support; the poisoned patient who is hypotensive needs fluids and vasopressors while the antidote is being prepared.