drugs and their classification class 12 | On the basis of drug action , pharmacological effect chemical structure

drugs and their classification class 12 | On the basis of drug action , pharmacological effect chemical structure

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Chemical compounds are certainly central to our lives. Hydrocarbons (compounds composed only of carbon and hydrogen) are used as fuel to power our cars and to heat our homes. Our bodies are fueled with compounds obtained from the food we eat in the form of sugars (carbohydrates), fats and proteins. This food is made more palatable by flavorings, is wrapped in plastic and is kept from spoiling with preservatives. Our clothes are made of organic compounds, out of which some come from plant and animal sources (cotton and wool) or are synthetic (nylon and dacron). These fabrics are made colorful with dyes. The other applications of chemistry are paints and varnishes, dyes, soaps and detergents, cosmetics, etc. When we are ill, we take drugs that may also be organic: aspirin relieves headaches, codeine suppresses coughs, and diazepam (valium) calms nerves. The applications of chemistry include cures for many diseases that have plagued the human race for thousands of years. Eventually, it may lead to a cure or vaccine for AIDS. These are only a few examples of how we use chemicals daily. In modern times, chemistry is being applied to produce materials for space travel, fuels and rocket propellants, all sorts of building materials, synthetic fibers, microchips for computers, and explosives and chemical weapons. Living organisms – from microbes to humans – have a range of chemical substances varying in complexity from water and simple salts to DNA (deoxyribonucleic acid) molecules containing tens of thousands of atoms. Four of the chemical elements – hydrogen, carbon, nitrogen and oxygen – make up approximately 95% of the mass of living matter. Small amounts of sulphur, phosphorus, calcium, sodium, potassium, chlorine, magnesium and iron, together with trace amounts of many other elements such as copper, manganese, zinc, cobalt and iodine, are also found in living organisms. In this chapter, we will focus on applications of chemistry to drugs, food additives and cleansing agents.

DRUGS AND THEIR CLASSIFICATION

Drugs are chemicals of low molecular masses (-100-500 μ) whose intake by a living system has a physiological effect. If the drug helps in treatment of disease and reduces pain and suffering of the body, it is known as a medicine. This branch of science which deals with treatment of various diseases with suitable chemical substances is known as chemotherapy. Each drug has a specific dose for a particular organism in which it can be considered safe. Beyond this dose, the same drug may be toxic and behave like a poison.

Classification of Drugs

The drugs are classified on the following basis:

1. On the basis of pharmacological effect : This classification is based on the effect of the drug on biolog
ical systems. Some examples include analgesics which are used as pain relievers, antipyretics to bring down body temperature and antibiotics to restrict the growth of microorganisms and prevent spread
of infection.

2. On the basis of drug action : This classification is based on the effect of the drug on particular biochem
ical process. For example, COX (cyclooxygensae) inhibitors affect the action of enzyme cyclooxygensae which causes inflammation and pain. Similarly, antihistamines inhibit the action of histamine by blocking it from attaching to histamine receptors. Histamines produce symptoms of allergic reaction, such as runny nose or watery eyes, by increasing vascular permeability that results in flow of fluids
from capillaries into the tissues.

3. On the basis of chemical structure : Drugs with similar chemical structures have similar actions on
biological systems, for example, sulphonamides.

 

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