NEET Chemistry Notes Chemistry in Everyday Life – Chemicals in Medicines
Chemicals in Medicines
Chemicals in Medicines
Drugs are chemicals of low molecular masses (~ 100 to 500μ) which interact with macromolecular targets (carbohydrates, proteins and nucleic acids) to produce a biological response. When the biological response is therapeutic and useful, these chemicals are called medicines. Use of such chemicals to cure a disease or to prevent it, is called chemotherapy. These medicines are used in diagnosis, prevention and treatment of diseases.
Drugs can be classified mainly on criteria outlined as follows:
- On the basis of pharmacological effect It provides the whole range of drugs available for the treatment of a particular type of problem, e.g. analgesics have pain killer effect, antiseptics kill or arrest the growth of microorganisms.
- On the basis of drug action It is based on the action of a drug on the particular biochemical process, e.g. antimicrobials, neurologically active drugs, etc.
- On the basis of chemical structure Drugs classified in this way share common
structural features and often have similar pharmacological activity, e.g. sulpha drugs, arsenic drugs. - On the basis of molecular targets Drugs are classified on the basis of their
interaction with biomolecules such as carbohydrates, lipids, proteins and nucleic acids. - Drugs which can block the binding site of the enzyme and prevent the binding of substrate or can inhibit the catalytic activity of the enzyme are called enzyme inhibitors.
- Drugs which can compete with the natural substrate for their attachment on the active sites of enzymes are called competitive inhibitors.
Different Classes of Drugs
Some important classes of drugs are given below :
Antacids
- Treatment for acidity was administration of antacids.
- Antacids raise the pH of stomach to some appropriate level.
- Sodium hydrogen carbonate, a mixture of aluminium and magnesium hydroxide etc., are the commonly used antacids.
Antihistamines
- Antihistamines or antiallergic drugs are used as treatment for allergies.
- Allergies are caused by an excessive response of the body to allergens (the substances causes allergies).
- Excessive secretion of histamines, a chemical secreted by mast cells in body, also causes allergy, e.g. diphenylhydramine, chlorpheniramine, promethazine etc.
- Some synthetic drugs, brompheniramine (dimetapp) and terfenadine (seldane), also act as antihistamines.
- Histamine also stimulate the secretion of gastric juice (in stomach) but antihistamines do not affect this secretion because antiallergic and antacid drugs work on different receptors.
Neurologically Active Drugs
Tranquilizer It is a class of chemical compounds used for the treatment of stress, mild and severe mental diseases. These are commonly called psychotherapeutic drugs. These are the essential component of sleeping pills.
Some examples according to the action of drugs are
- Antidepressant drugs, e.g. iproniazid, phenelzine etc., are used to reduce depression.
- Chlorodiazepoxide and meprobamate, are relatively mild tranquillisers, suitable for relieving tension. Equanil is used in controlling depression and hypertension.
- Barbiturates such as seconal, luminal, veronal are hypnotic (sleep producing) drugs while valium and serotonin, are non-hypnotic drugs.
- Reserpine, a tranquilliser is obtained from Indian plant Rauwolfia serpentina.
Analgesics These reduce or abolish pain. These are classified as follows :
- Non-narcotic (non-addictive) analgesics, e.g. aspirin and paracetamol are analgesics as well as antipyretics (fever reducing).
- Aspirin (acetyl salicylic acid) and paracetamol (N-acetyl-p-amino phenol) are non-narcotic (non-addictive) analgesics. Aspirin inhibits the synthesis of chemicals, known as prostaglandins which stimulate inflammation in the tissue and cause pain. Because of its anti blood clotting action, aspirin is also used in the prevention of heart attacks.
- Narcotic analgesics, e.g. morphine, heroin (morphine diacetate), codeine, etc.