Download Short Note of Chemistry in Everyday Life for CBSE Exams:

CHEMICALS IN MEDICINES

Drugs: These are the chemicals of low molecular masses ( 100-500 u) which interact with macromolecular targets and produce a biological response.

Medicines: These are the drugs that are therapeutic and used for diagnosis, prevention, and treatment of diseases.

The use of chemicals for therapeutic effect is called chemotherapy.

Classification of drugs: Drugs are classified on the basis of

Drug Target Interaction:

Enzymes as a drug target: Drugs inhibit any of the two activities of the enzymes, they can block the binding site of the enzyme and prevent the binding of the substrate or they can inhibit the catalytic activity of the enzyme.

Receptors as a drug target: Proteins that transmit the communication to the different parts of the body are called receptors. Receptor proteins are embedded in the cell membrane and the receptor changes its shape to accommodate a chemical messenger which brings about transfer of message into the cell.

Drug interact with receptors in two ways:

– Drugs bind to their receptor sites and inhibit its natural function (antagonists). These are useful when blocking of the message is required.

– Some drugs mimic the natural messenger by switching on the receptor (agonists). These are useful when there is a lack of natural chemical messenger.

The therapeutic action of different classes of drugs:

Antacids: These are chemicals that neutralize excess acid in the gastric juices and give relief from acid indigestion, acidity, heartburns, and gastric ulcers, e.g., magnesium hydroxide, calcium carbonate, etc.

Antihistamines: They diminish or abolish the main action of histamine released in the body and hence, prevent allergic reactions, they are also called antiallergic drugs, e.g., diphenhydramine (Benadryl), pheniramine maleate (avil), etc.

Tranquilizers: These are chemical substances used for the treatment of stress, mild and severe mental diseases. They are neurologically active drugs and are also called psychotherapeutic drugs, e.g., veronal Amytal, Seconal, Equanil, chlordiazepoxide, etc. Veronal, Amytal, and Seconal are called barbiturates. Barbiturates are hypnotic, i.e., sleep producing agents.

Analgesics: These are chemical substances that reduce pain. They are classified as:

Non-narcotic analgesics: Aspirin and paracetamol belong to this class of drugs. They are e_ective in relieving skeletal pain such as that due to arthritis. They have many other effects such as reducing fever and preventing platelet coagulation. Aspirin finds use in the prevention of heart attacks because of its anti-blood clotting action.

Narcotic analgesics: Morphine and many of its homologs, when administered in medicinal doses, relieve pain and produce sleep. In poisonous doses, they cause convulsions and ultimately death. These are mainly used for the relief of post-operative pain, cardiac pains and pains of terminal cancer.

Antimicrobials: These are chemical substances used to cure infections due to microorganisms, e.g., sulphadiazine, sulphadoxine, etc. Antibiotics, antiseptics, and disinfectants are antimicrobial drugs.

Antibiotics: These are chemical substances produced wholly or partly by chemical synthesis which in low concentration inhibit the growth or destroy microorganisms by intervening in their metabolic processes.

The antibiotics may be either bacteriocidal (kill the organisms in the body) e.g., penicillin, o_oxacin, etc., or bacteriostatic (inhibit the growth of organisms), e.g., erythromycin, chloramphenicol, etc.

Antibiotics that kill or inhibit a wide range of Gram-positive and Gramnegative bacteria are said to be broad-spectrum antibiotics, e.g., tetracycline, chloromycetin and chloramphenicol.

Those e_ective mainly against Grampositive or Gram-negative bacteria are narrow-spectrum antibiotics, e.g., penicillin-G.

Antiseptics: These are chemicals which either kill or prevent the growth of microorganisms and are applied to the living tissues such as wounds, cuts, ulcers and diseased skin surfaces.

Dettol is a commonly used antiseptic and it is a mixture of chloroxylenol and terpineol y Bithionol is added to soaps.

Tincture of iodine, i.e., 2-3% solution in the alcohol-water mixture is applied to wounds.

Disinfectants: These are also used to kill microorganisms, but they are applied to inanimate objects.

Some substances can act as antiseptic as well as a disinfectant by varying the concentration.

0.2% phenol is an antiseptic, whereas its 1% solution is disinfectant.

0.2-0.4 ppm chlorine in aqueous solution acts as a disinfectant.

Antifertility drugs: Chemical substances used to prevent conception or fertilization are called antifertility drugs. These are essentially a mixture of estrogen and progesterone derivatives which are more potent than the natural hormones, e.g., mifepristone, ormeloxifene, etc.