Why do we need to classify the drugs in different ways ?

Explanation

Drugs are to be classified in different ways, depending upon the need of the doctor who want to prescribe a particular drug for his patient or the medicinal chemist who want to design a suitable molecule for a particular disorder etc.
Drugs can be classified mainly on the basis given below :
1. On the basis of pharamacological effect : This classification is based on pliaramacological effect of the drugs. It is useful for doctors because it provides them the whole range of drugs available for the treatment of particular type of problem. For example, analgesics have pain killing effect, antiseptics kills or arrest the growth of microorganisms etc.
2 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 histamine can be blocked. There are different antihistamines which block the action of histamine in different ways. For example, certain antihistamines prevent the interaction of histamine with the receptors while other compete with histamine for binding sites on receptors where histamine exerts its effect.
3. On the basis of chemical structure : It is based on the chemical structure of the drug. Drugs classified in this ways share common structural features and often have similar phramacological activity. For example, sulphonamides have common structural feature, as shown below:

4. 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 same 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.