Principles of antidote therapy

What it is

An antidote reduces or reverses the effect of a poison. It can do that in three ways: absorption prevention, binding to the poison and neutralizing it directly, and antagonizing the end organ-effect. The examples named are N-acetyl cysteine, naloxone, oxygen and atropine.

How it is treated

The toxicology table sets each poison beside its own specific treatment.

Opioids (heroin, morphine, oxycodone, fentanyl) are treated with naloxone IV/IM, repeated as needed, and fentanyl may need multiple naloxone doses. Acetaminophen (paracetamol) is treated with N-acetylcysteine (NAC), PO or IV, and NAC is most effective within 8 hours. Benzodiazepines have flumazenil, which is rarely used. TCA (tricyclics) and salicylate are both treated with IV sodium bicarb, and salicylate with dialysis as well if severe.

Beta-blockers are treated with IV glucagon, atropine and pacing, and glucagon is named the best initial antidote. Calcium channel blockers are treated with IV calcium gluconate or chloride, glucagon and insulin. Digoxin is treated with digoxin-specific Fab fragments, which are used for arrhythmia, K >5, or hemodynamic instability. Organophosphates (pesticides) are treated with atropine and pralidoxime (2-PAM): atropine is given until the secretions are dry, and pralidoxime reverses the paralysis. Anticholinergics have physostigmine, in severe cases only. Sympathomimetics (cocaine, amphetamines) are treated with benzodiazepines.