toxicology general principals of poisoning

1. Antidotes and its clinical
application
Presented to:-
Mr. ARINJAY JAIN
Presented by:-
MOHD. FARHAN SHEHZAD
(TPH1812003)
KRITI JAIN
(TPH1812004)

2. Antidotes
• An antidote is a substance which can counteract a form of
poisoning. The term ultimately derives from the Greek
“pharmakon antidoton”medicine given as a remedy.
• In the majority of cases of acute poisoning, all that is
required is intensive supportive therapy.
• Specific antidotes are rarely necessary, besides the fact that
only a few genuine antidotes exist in actual practice,
though there is no denying the dramatic results that can be
achieved with some of them in appropriate circumstances.
• Proper antidotal therapy can be life-saving in some
situations.

3. Mechanisms of action
• Antidotes work in any one of a number of ways.
Common modes of action are as follows:
1. Inert complex formation
2. Accelerated detoxification
3. Reduced toxic conversion
4. Receptor site competition
5. Receptor site blockade
6. Toxic effect bypass

4. 1. 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, dicobalt edetate
for cyanide,
etc.

5. 2. Accelerated detoxification
Some antidotes accelerate the detoxification of a
poison,
e.g. thiosulfate accelerates the conversion of
cyanide to nontoxic thiocyanate, acetylcysteine
acts as a glutathione substitute
which combines with hepatotoxic paracetamol
metabolites and
detoxifies them.

6. 3. Reduced toxic conversion
The best example of this mode of action is
provided by
ethanol which inhibits the metabolism of
methanol to toxic
metabolites by competing for the same
enzyme (alcohol dehydrogenase).

7. 4. Receptor site competition
Some antidotes displace the poison from
specific receptor
sites, thereby antagonising the effects
completely. The best
example is provided by naloxone, which
antagonises the effects
of opiates at stereo-specific opioid receptor
sites

8. 5. Receptor site blockade
This mode of action is best exemplified by
atropine which
blocks the effects of anticholinesterase agents
such as organophosphates at muscarinic receptor
sites.
6. Toxic effect bypass
An example of this type of antidotal action is
provided by
the use of 100% oxygen in cyanide poisoning.

9. Poison Antidote
Acetaminophen / paracetamol Acetylcysteine
Anesthetics, local lipid emulsion
Aniline Methylene blue
Anticholinesterases (organophosphates) atropine, pralidoxime
Antidepressants ,cyclic (TCAs) Sodium bicarbonate
Antidepressants, noncyclic Sodium bicarbonate
Arsenic Dimaval
Benzodiazepines Flumazenil
Beta blockers Atropine, inuslin, calcium, glucagon
Black widow spider Black widow spider antivenin
Calcium channel blockers Atropine, insulin, calcium,
Cyanide Hydroxocobalamin
Digoxin Atropine , digosin immune fat
Ethylene glycol pyridoxine, sodium bicarbonate

10. Poison Antidote
Glycol ethers fomepizole
Hydrofluronic acid burns Calcium gluconate
Iroon Deferoxamine
Isoniazid Pyridoxine
Lead Dimaval
Mercury Dimaval
Methanol Fomepizole
Mushrooms, hepatotoxic Acetylcysteine
Mushrooms, seizure-inducing Pyridoxine
Nitrates Methylene blue
Nitrites Methylene blue
Opioids Naloxene
Organophosphate insecticides Atropine pralidoxime
salicylates Sodium bicarbonate

11. Adjuvant antibiotics
Agent Indications
Benzatropine Dystonia
Chlorpromazine Psychotic states
Corticosteroids Acute allergic recation
Diazepam Convulsions
Diphenhydramine Dystonia
Dopamine Myocardial depressions, vascular
relaxation
Epinephrine Anaphylactic shock, cardiac arrest
Glucose Hypogycaemia
Lidocaine Ventricular arrhythmias

12. Obselete antidotes
• Unfortunately in India, cumbersome
governmental regulations and a lack of economic
incentives for manufacturers have restricted
availability of a substantial number of these
life-saving drugs.
• As a result, doctors still use some substances
which are more readily available as antidotes, but
are generally considered obsolete or even
dangerous in Western countries.

13. Agent Indication
Copper sulfate Phosphorus
Cysteamine Paracetamol
Diethyldithiocarbamate Thallium
Fructose Ethanol
Levallorphan Opiates
Nalorphine Opiates
Silibinin Amanitin
Tocopherol Paraquat
Universal antidotes Ingested poison

14. Role of antidote in poisoning
• Antidotes may play an important role in the treatment of poisoning.
While good supportive care and elimination techniques may, in
many cases, restore a poisoned patient to good health and stabilize
his or her body functions, the appropriate use of antidotes and
other agents may greatly enhance elimination and counteract the
toxic actions of the poison In certain circumstances they may
significantly reduce the medical resources otherwise needed to
treat a patient shorten the period of therapy, and, in some cases,
save a patient from death.
• Thus antidotes may sometimes reduce the overall burden on the
health service of managing cases of poisoning.
• In areas remote from good hospital services, and particularly in
developing countries that lack adequate facilities for supportive
care, antidotes may be even more essential in the treatment of
poisoning

15. • In poisoning, emetics or the stomach pump are
indicated if the poison has not yet been absorbed, and
where other less severe means are not effective.
• In order to produce vomiting warm water may be
given, or, if necessary, a tablespoonful of mustard
stirred to creamy consistency with water, this to be
followed by large draughts of water.
• Generally this is later followed by demulcent drinks,
such as flaxseed, whites of eggs beaten tip in water.
slippery elm, etc. No emetics should be given, however,
in poisoning by acetic, hydrochloric or muriatic, nitric
and sulphuric acid.

16. Universal antidote
• A mixture of 50% activated charcoal, 25% magnesium
oxide, and 25% tannic acid, formerly thought to be useful
as an antidote for most types of acid, heavy metal, alkaloid,
and glycoside poisons.
• It is now believed that the mixture is no more effective
than activated charcoal given with water. The chemical
nature of amorphous carbon combined with a high surface
area and porosity makes it an ideal medium for the
adsorption of organic chemicals.
• Activated charcoal is administered orally and functions by
adsorbing molecules of complex organic compounds,
thereby preventing the absorption of the potential toxicant
from the GI tract and sequestering it to be eliminated in the
feces.

17. • Activated charcoal is normally used as an oral adjunct to more
direct antidotal therapy during treatment of poisoning in animals.
Animals showing signs of acute intoxication should be treated with
a more specific antidote initially.
• In many cases there will not be a specific antidote and preventative
measures such as gastric protection and antibiotics may be needed.
• Activated charcoal should not be given simultaneously or shortly
before the oral administration of other therapeutic agents such
Prepared by the Veterinary Technical Service Department of LLOYD,
Inc.. Shenandoah, lowa as antibiotics, vitamins or amino acids.
• Antibiotic therapy should be administered parenterally when
activated charcoal is used. Fluids to correct acid/base, hydration
and electrolyte imbalances should be administered.

18. THANK YOU