An antidote is an agent that counteracts the effects of a poison, toxin, or harmful substance on the body. They are specifically designed to neutralise or reverse the toxic effects caused by the substance, mitigating or preventing further harm and promoting recovery.
Antidotes work by various mechanisms, including binding to the toxic substance, blocking its action on target organs or systems, enhancing elimination from the body, or restoring normal physiological functions. The administration of an antidote is typically guided by the specific toxic agent involved and is an essential aspect of medical management in cases of poisoning or overdose.
Although antidotes have a surprisingly minor role in managing most poisonings, with their use restricted to specific indications, knowledge of them is commonly tested in medical exams at both undergraduate and postgraduate levels, including the MRCEM examination.
A summary of the most commonly used and encountered antidotes is outlined in the table below:
| Poison | Antidote |
|---|---|
| Benzodiazepines | Flumazenil |
| Beta-blockers | Atropine Glucagon Insulin |
| Carbon monoxide | Oxygen |
| Cyanide | Hydroxocobalamin Sodium nitrite Sodium thiosulphate |
| Ethylene glycol | Ethanol Fomepizole |
| Heparin | Protamine sulfate |
| Iron salts | Desferrioxamine |
| Isoniazid | Pyridoxine |
| Methanol | Ethanol Fomepizole |
| Opioids | Naloxone |
| Organophosphates | Atropine Pralidoxime |
| Paracetamol | Acetylcysteine Methionine |
| Sulphonylureas | Glucose Octreotide |
| Thallium | Prussian blue |
| Warfarin | Vitamin K Fresh frozen plasma (FFP) |
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