Chemistry Drugs and Their Classification
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### Topics Covered :

● Introduction
● Drugs and Their Classification
● Classification of Drugs
● On the Basis of Pharmacological Effect
● On the Basis of Drug Action
● On the Basis of Chemical Structure
● On the Basis of Molecular Targets

### Introduction :

=> Chemistry has influenced our life so much that we do not even realise that we come across chemicals at every moment; that we ourselves are beautiful chemical creations and all our activities are controlled by chemicals.

=> The principles of chemistry have been used for the benefit of mankind.

=> Think of cleanliness — the materials like soaps, detergents, household bleaches, tooth pastes, etc. will come to your mind.

=> If we look towards the beautiful clothes —cchemicals of the synthetic fibres used for making clothes and chemicals giving colours to them will come to your mind.

=> Sickness and diseases remind us of medicines — again chemicals.

=> Explosives, fuels, rocket propellents, building and electronic materials, etc., are all chemicals.

### Drugs and their Classification :

color{green}("Drugs ") : Drugs are chemicals of low molecular masses (~100 – 500u).

● These interact with macromolecular targets and produce a biological response.

color{green}("Medicines ") : When the biological response is therapeutic and useful, these chemicals are called medicines and are used in diagnosis, prevention and treatment of diseases.

color{green}("Note ") : If taken in doses higher than those recommended, most of the drugs used as medicines are potential poisons.

● Use of chemicals for therapeutic effect is called chemotherapy.

### Classification of Drugs :

Drugs can be classified mainly on criteria outlined as follows :

### On the basis of pharmacological effect :

=> This classification is based on pharmacological effect of the drugs.

=> It is useful for doctors because it provides them the whole range of drugs available for the treatment of a particular type of problem.

=> For example, analgesics have pain killing effect, antiseptics kill or arrest the growth of microorganisms.

### On the basis of drug action :

=> It is based on the action of a drug on a particular biochemical process.

=> For example, all antihistamines inhibit the action of the compound, histamine which causes inflammation in the body.

=> There are various ways in which action of histamines can be blocked.

### On the basis of chemical structure :

=> It is based on the chemical structure of the drug.

=> Drugs classified in this way share common structural features and often have similar pharmacological activity.

=> For example, sulphonamides have common structural feature, given in fig.

### On the basis of molecular targets :

=> Drugs usually interact with biomolecules such as carbohydrates, lipids, proteins and nucleic acids.

=> These are called target molecules or drug targets.

=> Drugs possessing some common structural features may have the same mechanism of action on targets.

`=>~ The classification based on molecular targets is the most useful classification for medicinal chemists.