ANTIDOTES

Antidote | Pharmacare Academy

     Antidote

                              
DEFINITION

It is defined as the "drug or chemical agents which is used to reverse or stop the action of poisons are known as antidote". 

Poisoning may occur due to the presence of lead, heavy metal, arsenic, overdose of drug,contamination of food and water etc.

Antidotes are applied according to the following:

• local antidote:

Local antidote or drug react with poison in the stomach and inactivate it's absorptions.

• Systematically

Systematic antidote use to alter or reverse the action of absorb poison.

Some common example of antidotes are:

• Sodium nitrite (NaNO2)
• Magnesium sulphate (MgSO4)
• Sodium thiosulphate ( Na2S2O3) &
• Kaolin.

Classification of antidotes:
Antidotes are classified on the basis of their mechanism of action, on the basis of mechanism of action they are classified as follows:

                                     

                                     Physiological  antidote

                                     Chemical antidotes &
                                     Mechanical antidotes.

Explanation

• Physiological antidote:

They produced opposite effect and alter the effect of that poison by producing some other physiological effect
Example: Sodium nitrite in cyanide poisoning.

• Chemical antidote:

These types of agent is used to convert the chemical nature of the position into some other less toxic compound which is not harmful of the body and it is easily eliminated by excretory system of the body.
Examples: Sodium thiosulphate in cyanide poisoning.

• Mechanical antidote:

These drug or agents used to prevent the absorption of position in GIT expelling the position through urine or vomiting.
( Note: This type of antidote induce emesis. )
Example: Activated charcoal

Cyanide poisoning:
Poisoning due to cyanide containing compound is termed as cyanide poisoning cyanide is a binary compound and contains cyanogen( CN^-) radical.
(CN^-) radical has a high affinity with potassium, hydrogen Sodium and ferric radical therefore it form highly portions compound.

• Cyanide poisoning occur due to Ingestion or inhalation of inorganic cyanide salt.

Example: KCN, HCN and NaCN.

SODIUM NITRITE
Molecular formula: NaNO2

Molecular weight: 69.0 u.
I.P. limit: Sodium nitrite contain not less than 97% or not more than 101 % of NaNO2.

Preparation of sodium nitrite:

• It is prepared by thermal decomposition of sodium nitrate.

             Heat
2NaNO3-----------> 2NaNO2 + O2

• It is also prepared by heating of sodium nitrate with metallic lead or Carbon at lower temperature.

                   Heat
NaNO3 + Pb--------> NaNO2 + PbO
                    Heat
2NaNO3 + C----------> 2NaNO2 + CO2

Physical properties or characteristics of sodium nitrite:

• It occurs as white or slightly yellow granules powder or fused masses or sticks.
• It is odourless.
• It has saline test.
• It has deliquescent that is hygroscopic property.
• It is soluble in water and partly soluble in alcohol.

Chemical property of sodium nitrite:

• It act as a reducing as well as oxidizing agent.
• Sodium nitrate react with sulphuric acid to form nitrous Acid.

2NaNO2+ H2SO4 ----------> 2HNO2 + Na2SO4                           
                                         ( nitrous acid )

Uses of sodium nitrite:

• Sodium nitrate is used in the treatment of Cyanide poisoning along with sodium thiosulphate.
• It is used as a rust inhibitor.
• It act as a food preservative such as  cured and meat product.

Qus (a) Defined the term antidote? How it can be applied,and write the step involved in the treatment of Cyanide poisoning?
(b) Write the complete account of sodium nitrite? (8 + 8 FAQ's )
Ans: (a) Defined the term antidote: refer to basic point.
How it can be applied: Refer to basic point.

• Step involved in the treatment of cyanide poisoning:

For the treatment of cyanide poisoning there are two inorganic antidotes such as sodium nitrite and sodium thiosulphate are used along with each other.

• First of all the intravenous infusion of sodium nitrite injection is given after that sodium thiosulphate infusion gives intravenously.
  
• Sodium nitrite is able to convert hemoglobin to methaemoglobin,  which binds with cyanide Ion does cyanide poisoning of cytochrome oxidase get prevented,which is the main toxic actions of the cyanide. However cyanide- methaemoglobin compound get dissociate slowly.
• At the same time sodium thiosulphate immediately convert it into non-toxic thiocyanate which get excreted by kidney.

Sign & symptoms:

( Note: Sodium nitrite and sodium thiosulphate as a toxic substance hence it applied only when cyanide poisoning is confirmed. )

Ans(b) : refers to write the complete monograph of Sodium nitrite as discussed above.


Image courtesy: Google images
Books reference: GR Chatwal , Mhod Ali