Explain the different classifications of drugs.

Ans:-Drugs are classified depending on following criteria.

1)  On the basis of drug action:

Depending on the biochemical action of drugs, they are classified as antihistamines, cardiovascular drugs, sedatives, hypnotics etc.

2)   On the basis of molecular targets:

Drugs interact with biomolecules such as carbohydrates, lipids, proteins and nucleic acids. These molecules are called target molecules or drug targets. Drugs may be classified depending on the nature of target molecules.

3)  On the basis of chemical structure:

Drugs may be classified depending on its chemical structure. Drugs having similar structural features may have similar pharmacological activity.

4)  On the basis of pharmacological action:

Drugs may be classified depending on its pharmacological effect. It is useful for doctors because it gives whole range of drugs available for treatment of particular type problem. Ex: Analgesics have pain killing effect,  Antiseptics kill microorganism.

Discuss about (1) analgesics   (ii) antipyretics.


1) Analgesics : Analgesics reduce or abolish pain without causing disturbances of nervous system. They are classified as (a) Narcotic analgesics (b) Non-narcotic analgesics.

a) Narcotic analgesics:

1)   Narcotic analgesic act as strong analgesics and cause depression of central nervous system.

2)   Narcotic drugs are addictive drugs and euphoria produced by them is main factor in their addictive property.

3)   Narcotics like morphine, codeine, heroine etc., relieve pain and produce sleep in medicinal doses. In high doses they produce stupor, coma, convulsions and finally death.

4)   These analgesics are chiefly used for relief of post operative pain, cardiac pain, cancer pains.

b) Non-narcotic analgesics:

1)   Analgesic use of non-narcotics is limited to mild aches and pains like backache and headache and they have no addictive properties.

2)   Aspirin and Ibuprofen belong to this class of analgesics.

3)  Acetyl salicylic acid is called aspirin. It is prepared by acetylation of salicylic acid.

Aspirin is analgesic, antipyretic and anti-inflammatory. It is used for headache, fever, muscular pains and aches.

4)  Ibuprofen is an anti-inflammatory drug that possesses anti-pyretic and analgesic effects. Its structure is as shown below.

It is used for treatment of rheumatoid and osteoarthritis.


Write note on (1) antimicrobials   (2) antiseptics   (3) disinfectants.

1) Antimicrobials:

Micro organisms like bacteria, virus, fungi cause diseases in humans and animals.

The organism that causes diseases is called a pathogen. The pathogenic action of microbes can be controlled by

1)   Using drug that kills microorganism.

2)   Using drug that inhibits growth of microorganism.

3)   Increasing immunity and resistance in the body.

The drugs which can kill or inhibit the growth of microbes such as bacteria, virus, fungi and other parasites are called antimicrobials.

Antibiotics are used as antimicrobials.

2)  Antiseptics: 

Antiseptics are compounds that kill or prevent the growth of microorganisms. These are applied to living tissues like wounds, cuts, ulcers and diseased skin surfaces.

Ex :      1) Dettol – It is mixture of chloroxylenol and terpinol.

2)  Bithional – antiseptic in soaps.

3)  Tincture of Iodine – 2-3% Iodine in alcoholic aqueous solution.

4)  Boric acid – antiseptic for eyes.

3)   Disinfectants:

The chemical compounds used for killing or preventing the growth of microorganisms are called disinfectants. They are used to floors, drainage systems etc.

Ex :     1) 1% phenol solution.

2)  Aqueous solution of 0.3 ppm chlorine solution.

3)  Formalin

Explain the antacids, antihistamines, and food preservatives.                      

1) Antacids: Chemicals which remove excess acid in stomach maintain pH at normal level are called antacids.

Weak bases like magnesium hydroxide, magnesium carbonate, aluminium hydroxide gel, sodium bicarbonate, aluminium phosphate are antacids.

Metal hydroxides that are slightly or insoluble are better antacids. These metal salt and hydroxide antacids control the symptoms but not the cause.

Recently used antacids are omeprazole and lansoprazole.

2)   Antihistamines:

Histamine is a chemical that stimulates the secretion of pepsin and hydrochloric acid in stomach. The drugs which prevent the interaction of histamine with its receptors present on stomach walls and thereby decreases amount of acid produced in stomach are called antihistamines.

Histamine is also responsible for nasal congestion with cold and allergic response to pollen, house dust, sheep wool, human hair etc.

The drugs Cimetidine, Ranitidine are used as antihistamines.

The synthetic drugs Bromopheniramine and Terfenadine act as antihistamines.

3)   Food preservatives:

The chemicals which are added to prevent the spoilage of food due to microbial growth are called food preservatives.

The most important food preservative is sodium benzbate. Salts of propionic acid and sorbic acid are also used as preservatives.

Anti-oxidants preserve food by retarding the action of oxygen because they are more reactive towards oxygen than food. The important anti-oxidants used are BHT (butylated hydroxytolune) and BHA (butylated hydroxy anisole)

Some dyes are used as edible colours for food. They have no nutritive value and sometimes are harmful for children and asthma patients.

Write note on 1) antibiotics 2) artificial sweetening agents.

1) Antibiotics : Antibiotics are chemical substances produced by microorganism which inhibit the growth or destroy microorganisms.

The first antibiotic discovered was pencillin by A. Fleming.

The antibiotics are either bactericidal or bacteriostatic.

Penicillin, aminoglycosides, ofloxacin are bactericidal killing antibiotics.

Erythromycin, Tetracycline, Chloramphenicol are bacteriostatic (inhibitory) antibiotics.

The complete range of microorganisms attacked by an antibiotic is called antibiotics broad spectrum.

Chloramphenicol is a broad spectrum antibiotic tetracycline, chloramphenicol and the penicillin mixture have a narrow spectrum.

2) Artificial sweetening agents:

Many people prefer to use artificial sweeteners because natural sweeteners like sucrose add to calorie intake.

Saccharin is 550 times sweeter to cane sugar. It is excreted in the urine unchanged and hence is very useful to diabetic patients and those who need to control intake of calories.

Aspartame is 100 times sweeter to sucrose. It is useful only for cold foods and soft drinks because it is unstable at cooking temperature.

Alitame is 200 times sweeter to sucrose. It is more stable than aspartame but the control of sweetness of food is difficult.

Sucrolose appears and tastes similar to sucrose but has no calorie addition. It is stable at cooking temperature.

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