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ANTIDOTE & ITS APLLICATIONS. Antidote - Definition. An antidote is defined as a remedy to counteract or neutralize the effects of a poison. In various poisonings, antidotes are used to counteract the pathophysiology produced by a toxin. Antidote - Classification.
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Antidote - Definition • An antidote is defined as a remedy to counteract or neutralize the effects of a poison. • In various poisonings, antidotes are used to counteract the pathophysiology produced by a toxin.
Antidote - Classification • Mechanical or Physical antidotes • Chemical antidotes • Physiological antidotes
Mechanical or Physical antidotes These antidotes counteract the effect of poison mechanically preventing their absorption without inactivating the damaging action of the poisons.
Mechanical or Physical antidotes • Activated charcoal • Demulcents • Bulky foods • Diluents
Mechanical or Physical antidotesDemulcents • Demulcents produce protective coating over the mucous membrane of stomach to protect it from the action of poison. • These are milk, egg white, starch, milk of magnesia and aluminium hydroxide gel.
Mechanical or Physical antidotesBulky foods • Bulky foods like Bananas, boiled rice or potatoes admixed with the poison and decreases its absorption. • The bulky foods are commonly used in ingestion of glass powder as these particles are embedded in them and prevent damage to the stomach mucosa.
Mechanical or Physical antidotesDiluents • Diluents such as water, milk or other similar drinks that dilute the poison and delay their absorption
Chemical antidotes The chemical antidotes disintegrate and inactivate poisons by undergoing chemical reactions along with the poisons and forming harmless or insoluble compounds.
Chemical antidotes • Weak non-carbonate alkalis • Weak vegetable acids • Albumen • Copper sulphate • Potassium permanganate • Tincture iodine or Lugol’siodine • Tannic acid
Physiological antidotes • These antidotes acts on the tissues or organs and antagonizes the actions of a poison. • Indicated in the condition, where poison have already been absorbed into the circulation. • Ex: Atropine for organophosphorus compounds • barbiturate for strychnine
Antidote - MOA • Inert complex formation • Accelerated detoxification • Reduced toxic conversion • Receptor site competition • Receptor site blockade • Toxic effect bypass
Antidote - MOA • Inert complex formation: • Some antidotes interact with the poison to form an inert complex which is then excreted from the body, • e.g. • chelating agents for heavy metals • Prussian Blue for thallium • specific antibody fragments for digoxin • dicobaltedetate for cyanide
Antidote - MOA 2. Accelerated detoxification Some antidotes accelerate the detoxification of a poison. e.g. • thiosulfate accelerates the conversion of cyanide to nontoxic thiocyanate • acetylcysteineacts as a glutathione substitute which combines with hepatotoxicparacetamol metabolites and detoxifies them.
Antidote - MOA 3. Receptor site competition • Some antidotes displace the poison from specific receptor sites, thereby antagonising the effects completely. • Ex: Naloxone for opioid poisoning at opioid receptors
Antidote - MOA 4. Reduced toxic conversion Some poisons are toxic and some poisons after metabolism, their metabolites are toxic. In such poisoning, the antidotes competes for metabolic enzymes and inhibits the metabolism of the poison, thereby decreasing the toxic effect Ex: Ethanol for methanol toxicity for aldehydedehydrogenase enzyme
Antidote - MOA 5. Receptor site blockade Antidotes blocks the receptor site of the poisons. Ex: Atropine blocks muscarinic receptor site for organophosphorous poisoning.
Antidote - MOA 6. Toxic effect bypass • An example of this type of antidotal action is provided by the use of 100% oxygen in cyanide poisoning.
