Antidote
Definition
A substance that counteracts a poison by competitive receptor block, enzymatic reactivation, chelation, immune binding or substrate replacement. Antidotes are class-specific, not generic.
- Mechanisms
- Receptor blockade, enzyme reactivation, chelation, immune binding, substrate replacement
- Specificity
- Class-specific, not a general poison reversal
- Example
- Naloxone for opioid receptor blockade
- Related example
- Pralidoxime for organophosphate enzyme reactivation
Common questions
Why can't one antidote treat every poisoning?+
Each antidote works by a mechanism matched to a specific class of toxin, such as blocking the same receptor the poison occupies or reactivating an enzyme the poison inhibited, so giving it against an unrelated poison does nothing and can itself be harmful.
Does giving the correct antidote always reverse the poisoning fully?+
Not always. Timing matters because some antidotes only work before the toxin causes irreversible damage, such as enzyme reactivators losing effectiveness once organophosphate binding has aged, so outcome depends on how early the antidote is given relative to exposure.
Related terms
- Atropinisation
- The clinical end point of titrated atropine therapy in cholinergic poisoning: drying of pulmonary secretions, clearing of crepitations, heart rate above 80,...
- DUMBBELS
- Mnemonic for the muscarinic side of the cholinergic toxidrome: Diarrhoea, Urination, Miosis, Bronchospasm and Bronchorrhoea, Bradycardia, Emesis, Lacrimation, Salivation.
- Oxime Reactivation
- Restoration of acetylcholinesterase function by pralidoxime (2-PAM) or obidoxime through cleavage of the organophosphate-enzyme bond, effective only before the enzyme is irreversibly...
- Specific Antidote
- An agent that acts on the poison's mechanism, not just on its symptoms. Naloxone for opioids, NAC for paracetamol, methylene blue for...
- Toxidrome
- A reproducible cluster of clinical findings (vital signs, pupil size, skin, bowel and bladder, mental status) that identifies a class of poison...