How does an Antidote Acts?


         According to World health organization Antidote is therapeutic substance which is used to counteract to the toxic substances or toxic action of a specific xenobiotic. These are interact with an ingested toxic substances to deactivate and remove from body. In another words antidotes counteract the undesirable effects of ingested toxins or toxic substances, accumulated toxic dose or over dose of active drug.

Antidotes act by different methods;
  • By neutralizing the poison or it’s toxic effect pharmacologically which means antagonistic action against  poison.
  • By converting them chemically to non-toxic or less toxic form
  • By adsorbing or absorbing and facilitate elimination from the site of action 
    An ideal antidote is specific for a particular poison because one antidote is not suitable for all poisons. When administered(taken) antidote  it has to reach the site where the poison has accumulated and exerting it’s toxic effect. antidote extract the toxic material from the bound state.The resulting complex between the toxic substance and antidote should be easily and fastly removed from the site and reach the eliminating. mostly kidneys involve in elimination process. when person take toxic substance first step is removal of toxic substance as much as by physically from the alimentary canal. If it is still present in the stomach second step is removal of toxic substance by inducing vomiting or by gastric lavage. In case toxic substance absorbed from body system some other methods are used.


Classification of Antidotes   

Antidotes are classified based on their mechanism of action, Three types

Physiological Antidotes 

These are counteract with toxic substance by bringing about physiological changes in the body
Example: sodium nitrite converts haemoglobin to methaemoglobin which binds to cyanide and inactivates it.


Chemical Antodotes

Chemical antidotes act by changing the chemical nature of poison or toxic substance.
Example:Sodium thiosulphate converts cyanide to thiocyanate, Thiocyanate is non-toxic form.

Mechanical Antidotes

Mechanical antidotes act by inhibiting the absorption of poison or toxin in the body.
Example: Activated Charcoal acts as absorbent which absorbs the poison and remove from body.


Some examples of Inorganic Antidotes

  Sodium nitrite 
  Sodium thiosulphate 
  Activated charcoal
  Light kaolin
  Disodium edetate
  Ammonium tetrathiomolybdate
  Triethyl tetraamine

General examples of antidotes for different toxic substances

      Toxic agents                                                                          Antidotes
Cyanide                                                             Tydroxycobalamin, sodium thiosulfate
Hydrofluoric acid                                                   Calcium Gluconate
Insulin                                                                                                            Glucose
Anticholinergics                                                      Physostigmine
Beta Blockers                                                              Glucagon
Methotrexate                                                           Leucovorin
Benzodiazepines                                                     Flumazenil
Magnesium Sulfate                                                Calcium Gluconate
Heparin                                                                   Protamine Sulfate
Tylenol                                                                                          Mucomyst
Opiates                                                                      Narcotic analgesics
Digoxin                                                                           Digibind
Acetaminophen                                                    n-Acetylcysteine 
Iron                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   Deferoxamine
Anticoagulants                                                         Vitamin K
Aspirin                                                                     Sodium bicarbonate
Isoniazid                                                                                       Pyridoxine
           When an accidental poisoning occurs, first line drug preferred is an Antidote. As these are highly specific against specific poisons, it shows high efficacy. Antidotes neutralize the poison either by adsorption and makes it non-toxic or eliminates the poison from the body. Be cautious and stay safe while dealing with toxic agents.

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