chemistry

CLASSIFICATION OF DRUGS

On the basis of drug action : Based on the action of drug in biochemical processes, drugs are classified into different categories such as antihistamines, sedatives, hypontic drugs etc. Histamine causes inflammation. To prevent inflamation antihistamines are used.

On the basis of molecular targets :

Based on the reaction of drug with biomolecules such as nucleic acids, proteins, lipids etc., these are classified into different types. These biomolecules are called target molecules. Drugs with similar structure have similar mechanism of action on biomolecular targets.

On the basis of chemical structure :

The drugs with common structural features have similar pharmacological activity.

 Sulphanamides have common structural aspects and therefore used for similar problems.

On the basis of pharmacological action :

Drugs are classified on the basis of pharmacological action. This enhances the range of drugs used by doctors for treatment of a perticular problem. For example, analgesics are used as pain killers .

Antiseptics are used to kill or prevent the growth of bacteria.

Antipyretics are used to control body temperature during fever.

Catalytic action of enzymes

Enzymes provide active sites for holding the substrate molecules through a variety of interactions like ionic bonding, hydrogen bonding, Vanderwaal’s forces and dipole-dipole interactions.

They also provide such functional groups that will attack the substrate to facilitate the chemical reaction as the reagent attacks.

Drug - enzyme interaction:

Drugs interact with the active sites on enzyme and inhibit the catalytic activity of the enzyme.

Drugs which act as competitive inhibitors, preferentially attach to the active sites prior to substrate

molecules.       (or)

Some drugs attach to sites other than active sites. They are called allosteric sites. By this attachment the shapes of active sites radically are affected so that the substrate molecules cannot recognise the active sites. Drugs block active sites.

Drug - Receptor Interaction

Receptors are proteins that are crucial to body’s communication process. These are present in cell membranes but a small active part of it projects out of the membrane. Chemical substances, which acta s messengers between neurons are received at the active projections and pass on the messages. Different receptors are selective towards chemical messengers since it depends on their shape, sturcture and amino acid composition of the receptor protein.

Drugs that bind to the receptor sites and inhibrit its natural function are called antagonists. These help to block message transfer when require. Some other types of drugs act as agonists and help transfer of message (or) even mimic natural chemical messengers. Thus these act as substitutes for the lack of chemical messengers in the body.