Toxicology & Immunosuppression/Antidotes & poisoning

Antidotes & poisoning

also: naloxone · flumazenil · NAC · vitamin K · DigiFab · antidote · overdose

Overview

The poison → antidote pairs — a high-yield, drillable set spanning every system. Includes the supportive principles (activated charcoal, urinary alkalinisation).

Mechanism

Each antidote counters its toxin: receptor antagonism (naloxone/flumazenil), substrate repletion (NAC → glutathione), chelation (desferrioxamine, dimercaprol), enzyme reactivation (pralidoxime), competition (fomepizole/ethanol at alcohol dehydrogenase), or specific binding (DigiFab, idarucizumab).

Indications

Specific poisoning / overdose
Reversal of drug effect

The agents

Paracetamol → N-acetylcysteineglutathione

Per nomogram/staggered criteria; the most-tested overdose.

Opioids → naloxoneantagonist

short t½

Titrate to respiratory rate; repeat/infuse.

Benzodiazepines → flumazenilantagonist

Caution — seizures (esp. mixed/dependent).

Warfarin → vitamin K (± PCC)

PCC (Beriplex) for major bleeding; heparin → protamine.

Digoxin → digoxin-specific antibody (DigiFab)

Iron → desferrioxamine; lead → dimercaprol/EDTAchelation

Organophosphates → atropine + pralidoxime

Methanol/ethylene glycol → fomepizole (or ethanol)ADH inhibitor

Beta-blocker/CCB → glucagon / IV calcium / high-dose insulin

Local anaesthetic → IV lipid emulsion; cyanide → hydroxocobalamin

DOAC → andexanet (Xa) / idarucizumab (dabigatran)

Adverse effects

Naloxone → acute opioid withdrawalcommon

Agitation, pain — titrate.

Flumazenil → seizuresserious

NAC → anaphylactoid reactioncommon

Cautions & contraindications

Flumazenil in mixed overdose / benzodiazepine dependenceall

Unmasks seizures.

Forgetting supportive careall

ABCDE, activated charcoal (within 1 h), urinary alkalinisation (salicylates), dialysis (lithium/salicylate/toxic alcohols).

Interactions

Monitoring & kinetics

Per toxin (levels, ABG, ECG); TOXBASE / National Poisons Information Service

Route per antidote. Drill this as poison→antidote (reverseCause).

Source: TOXBASE — Poisoning · BNF — Emergency treatment of poisoning