mechanism of antidote and examples

Therapeutic Uses

lPoisoning is very common in all human beings and to treat the poisoning the antidotes are used. In this resource I’ve tried to explain that what are antidotes and for what these are used, what is the mechanism of action of antidotes and what are the various uses of these.

Antidotes

An antidote is an agent which counteracts a poison. In the treatment of acute poisoning most patients require only supportive and symptomatic therapy. The active removal of poisons from the stomach by gastric lavage or emesis induction is done by the administration of substances like activated charcoal by mouth to reduce the absorption.

Techniques used to promote the elimination of poisons from the body such as forced diuresis, hemodialysis, or hemoperfusion are employed for a limited number of poisons. There are some specific antidotes and their use in appropriate circumstances can be life-saving. Such use does not preclude relevant supportive and symptomatic treatment.

Mechanism of Action of Antidotes

Antidotes act by different mechanism. The mechanisms of action of antidotes are given below:
1)Complex formation.

2)Metabolic conversion.

3)Prevention of toxic metabolite formation.

4)By changing the physio-chemical nature of toxicant.

5)Promotes return to normal function by repairing a defect or enhancing a function that corrects the effects of poison.

Classification of Antidotes

Depending on their action, antidotes are classified as:
1)Chemical Antidotes: Chemical antidotes are the agents which change the chemical nature of poison. For example, sodium thiosulphate which changes toxic cyanide to the non-toxic thiocyanate; sodium calcium edetate chelates agents used for heavy metal poison.

2)Physiological Antidotes: Physiological antidotes acs by producing the effect opposite to that of poison. For example, sodium nitrite converts hemoglobin into methemoglobin in order to bind cyanide.

3)Mechanical Antidotes: Mechanical antidotes which prevent the absorption of poison into the body. For example, activated charcoal absorbs the poison prior to absorption across intestinal wall. Copper sulphate, magnesium sulphate and sodium monohydrogen phosphate inactivate and precipitate the toxic material as insoluble salts by chelation.

Therapeutic Uses

Antidotes are used in treatment of poisoning as well as in case of over dose of drugs.

Following are the examples of antidotes which are used for treating poisoning:

Examples of Poisons and Antidotes

Poison/Drug(Antidote)

Paracetamol (acetaminophen)(N-acetylcysteine)

Anticoagulants, E.G., Warfarin(Vitamin K)

Opioids(Naloxone)

Iron (and other heavy metals) (Desferrioxamine, Deferasirox or Deferiprone)

Benzodiazepines(Flumazenil)

Ethylene Glycol(Ethanol, Fomepizole or Thiamine)

Methanol(Ethanol or Fomepizole)

Cyanide(Amyl Nitrite, Sodium Nitrite and Sodium 
Thiosulfate)

Organophosphates(Atropine and Pralidoxime)

Magnesium(Calcium Gluconate)

Calcium Channel Blockers 
(Verapamil, Diltiazem)(Calcium Gluconate)

Beta-Blockers 
Propranolol, Sotalol)(Calcium Gluconate and/or Glucagon)

Isoniazid(Pyridoxine)

Atropine(Physostigmine)