Antidote

D.pharmacy chapter covered in this pdf.

1. Ms. GopaleKalyaniS.

2. Definition:
According to WHO
“ Antidote was defined as a therapeutic substance used
to counteract the toxic actions of specified xenobiotic.”
Antidotes reduce the overall burden of health service
in managing of poisoning cases.
Supportive
Therapy
Correct
Antidote
Patient
survival

3. Classification of antidote:
According to site of action
According to mode of action
1.Physical
2.Chemical
3.Physiological/ Pharmacological

4. Classification of antidote:
According to Site of Action-
1.Interacts with poison to form a non-toxic complex
that can be excreted chelators.
2.Accelerates the detoxification of the poison. For eg.
N-acetylcystine, Thiosulfate.
3.Decrease the rate of conversion of poison into toxic
metabolite. For eg. Ethanol, Fomepizole.
4.Compete the poison for certain receptors.
Eg.Naloxone.
5.Block the receptor through which the toxic effects of
the poison is mediated. Eg. Atropine.

5. According to Site of Action-
6)Bypass the effect of poison. (Oxygen in treatment of
CO and cyanide toxicity).
7)Antibodies to the poison(Digibindand Antivenins).

6. According to mode of Action-
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
adsorbateon a surface of the adsorbent. For Eg.
Activated charcoal.

7. Physical Antidote:
b)Coating:A mixture of egg & milk make a coat over
the mucosa.
c)Dissolving: 10% alcohol or glycinefor carbolic acid.

8. Chemical Antidote:
Interact specifically with a toxicant or neutralisethe
toxicant.
Eg. Metal chelatorscombine with metals to form
complexes that can then be eliminated by the kidneys.
❖Mainly act by two mechanisms-
➢Complex Formation-
Antidote make complex with the toxicant making it unavailable to
cross the membrane or to interact with receptors.
•DMSA ( Dimercaptosuccinicacid ) are sulfohydralcompounds
that bind metal such as arsenic acid, lead etc.

9. Chemical Antidote:
Special binding agents like EDTA, defroxamine, and d-
penicillamineact by chelationof metal forming more water
soluble complex.
Antivenins and Antibodies against digitoxinare
immunologically generated agents that bind specifically to
the toxin or venom.
➢Metabolic Conversion-
Detoxification to less toxic product.
Nitrite interact with heamoglobinand cyanide to form
cyanomethamoglobin. Which is less toxic than cyanide and
interfere with the cyanide access to cytochromeoxidase
system.

10. Physiological Antidote:
They act by producing apposite effect to that of
poison.
Sodium Nitrite converts hemoglobin into
methemoglobinin order to bind cyanide.

11. Pharmacological Antidote:
Counteract the effects of poison by producing the
opposite pharmacological effects.
For Eg. ACHE inhibitors Atropine
Pharmacologic antidotes may neutraliseor antagonize
the effects of a toxicant.

12. Mechanisms-
This type of antidote may act by following 5
mechanisms:
1.Preventing the formation of toxic metabolite.
2.By facilitation of more rapid or complete elimination
of a toxicant.
3.By competing with toxicants action at receptor site.
4.By blocking receptors responsible for the toxic effect.
5.By aiding in the restoration of normal function.

13. Sodium Nitrite-
Sodium nitrite is an
inorganic compound. non-
cumbustiblebut will
accelerate burning of
cumbustiblematerial. If
large quantities are
involved in a fire or if the
cumbustiblematerial is
finely devided, an
explosion may result.
Act as anti-oxidant that is
used to cure meats.

14. Physical Properties-
Molecular Formula-NaNO2
Molecular Weight –69 g/mol
➢Physical Properties:
Colour–White to slightly yellowish crystalline powder.
Solubility-very soluble in water and soluble in alcohol.
Nature-Hygroscopic
Odour-Specific odour
Density-2.168 g/mol
PH-Between 7-9
Melting point-271 C

15. Chemical Properties-
In the laboratory , sodium nitrite can be used to destroy
excess sodium azide.
2NaN3 + 2NaNO2+2H 3N2 +2NO+2Na+2H2O
Above 330 C sodium nitrite decomposes (in air ) to sodium
oxide, nitric oxide and nitrogen dioxide.
2NaNO2 Na2O+ NO+ NO2
Sodium nitrite can be also used in the production of
nitrous acid via sulphuricacid .This reaction first yeilds
nitrous acid and sodium sulfate.
2NaNO2+ H2SO4 2HNO2 + NaSO4

16. Preparation:
The salt is prepared by treating sodium hydroxide with
mixture of nitrogen dioxide and nitric oxide.
NaOH+ NO2 + NO 2NaNO2 +H2O
The conversion is sensitive to the presence of oxygen,
which can lead to varying amounts of sodium nitrate.

17. Uses:
Sodium nitrite is used as part of an intavenousmixture
with sodium thiosulfateto treat cyanide poisoning.
The compound is toxic and mutagenic it will react
invivowith secondary or tertiary amines thereby
producing highly carcinogenic nitrosamines.
Indeed according to Healthsafety.org sodium nitrite
works with sodium chloride or salt to inhibit the
growth of clostridium botulinum. This is an organism
that can cause fatal food poisoning.
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