ppt of antidote

1. ANTIDOTES

2. Antidote
 According to WHO
“Antidote was defined as a therapeutic
substance used to counteract the toxic
action(s) of a specified xenobiotic.”
• Antidotes reduce the overall burden of health
service in managing of poisoning cases
 It includes
Supportive therapy +Correct antidote = Patient
survival

3. Classification of antidote-
• According to mode of action
• According to site of action

4. Classification of antidote- According
to mode of action
1. Physical
2. Chemical
3. Physiological/ Pharmacological

5. Classification of antidote- According
to site of action
1. Interacts with the poison to form a non toxic
complex that can be excreted e.g Chelators
2. Accelerates the detoxification of the poison e.g
N-acetylcystine, thiosulfate
3. Decrease the rate of conversion of poison into
toxic metabolite like Ethanol, fomepizole
4. Compete the poison for certain receptors
likeNaloxone
5. Block the receptor through which the toxic effect
of the poison is mediated likeAtropine
6. Bypass the effect of poison Oxygen in the
treatment of CO and cyanide toxicity
7. Antibodies to the poison : digibind and

6. PHYSICAL ANTIDOTE:
 Agent use to interfere with poison through
physical properties, not change their nature
a) Adsorbing: Adsorption is the adhesion of
atoms, ions, or molecules from a gas, liquid,
or dissolved solid to a surface. This process
creates a film of the adsorbate on the surface
of the adsorbent. The main example is
activated charcoal
b) Coating: A mixture of egg & milk make a
coat over the mucosa.
c) Dissolving: 10% alcohol or glycine for
carbolic acid

7. CHARCOL : (UNIVERSAL
ANTIDOTE)
• Produced by heating pulverized carbonaceous
substances sawdust, peat, or coconut shells
• Activation: hot air to erode the internal surfaces of the
product and thereby increase its adsorptive surface
area.
• Adsorption results from weak intermolecular (van der
Waals) forces
• AC can prevent systemic absorption of drugs when
given within 1- 2 h of ingestion
• the optimal dose is probably a 40:1 ratio (by weight) of
charcoal to drug
• Contraindicated for iron, lithium, potassium, and
ethanol overdose

8. CHEMICAL ANTIDOTE:
• Interact specifically with a toxicant, or neutralize
the toxicant. E.G. Metal chelators combine with
metals to form complexes that can then be
eliminated by the kidneys Mainly act by two
mechanisms:
1)Complex formation: Antidote make complex with
the toxicant making it unavailable to cross the
membrane or to interact with receptors
2) DMSA (dimercaprol and dimercaptosuccinic
acid are sulfohydral compounds that bind metal
such as arsenic acid ,lead.

9.  Sp. Binding agents like EDTA, defroxamine and
d-pencillamine act by chelation of metal forming
more water soluble complex
 Antivenins and antibodies against digitoxin are
immunologicaly genrated agents that bind
specifically to the toxin or venom
 Metabolic conversion:
Detoxification to less toxic product
 Nitrite interact with hemoglobin and cyanide to
form cyanomethamoglobin , which is less toxic
than cyanide and interfere with the cyanide
access to cytochrome oxidase system.

10. PHYSIOLOGICAL ANTIDOTE
• They act by producing opposite effect to
that of poison.
• Sodium nitrite converts hemoglobin into
methemoglobin in order to bind cyanide.

11. PHARMACOLOGICAL
ANTIDOTE
• Counteract the effects of a poison by
producing the opposite pharmacological
effects, e.g. ACHE inhibitors atropine
• Pharmacologic antidotes may neutralize or
antagonize the effects of a toxicant.
• This type of antidote may act by following 5
mechanism-

12.  1. Preventing the formation of toxic
metabolites:
More effective when given immediately before
toxic metabolic activation Example: Ethanol
and 4-methylpyrazole(4-mp) which compete
with the alcohol dehydrogenase which prevent
the formation of toxic intermediate from
ethylene glycol.
2. By facilitation of more rapid or complete
elimination of A toxicant :
Change the physiochemical nature of toxin,
allowing better glomerular filtration and
prohibit tubular reabsorption. e.g.
Molybdenum and sulfate for copper toxicity by

13.  3. By competing with the toxicant’s action
at a receptor site: a) Antagonism:
Competitive antagonism:
Naloxone/naltrexone: opioid dependence,
longer action and affinity for mu receptor.
Flumenazil: antagonist for benzodiazepine
Atropine: organophosphate, carbamate and
other parasympathomimetic antidote.
It is also used to correct bradycardia caused by
morphine, digitalis, beta blockers

14. non competitive antagonism:
calcium gluconate: used for calcium channel
blocker especially verapamil
1. black widow spider bite
2. lead colic
3. oxalic acid
paralidoxime : CHE activator act by breaking
alkyl phosphate che bond. it is used in
organophosphate toxicity.
diacetyl monoxyime(dam): action same as
pam but with more bbb penetration.

15. 4. By blocking receptors responsible for the
toxic effect :
The physiologic effect induced by a toxin is
prevented by an antidote, although the
toxicant is unchanged and may still be active.
Example:
Atropine blocks the physiologic effect of
acetylcholine at cholinergic synapse and
neuromuscular junction in organophosphate
toxicity

16. 5. By aiding in the restoration of normal
function: The antidote promotes return to normal
function by repairing a defect or enhancing a
function that correct the effect of poison.
Example:
Methylene blue: In nitrite poisoning, methylene
blue interact with reduced NADPH to reduce the
ferric iron of methemoglobin back to ferrous ion in
hemoglobin, which can again transport oxygen
Acetylcysteine : Acetylcysteine supplies the
precursor amino acids for glutathione, which
serves as biologic antioxidant against
acetaminophen toxicities

17. Thank you