Action Of Drugs

Drug is called as Oshadhi in Sanskrit (Osh means prepared by boiling and/or roasting) which means medicinal herb. A drug is usually prepared using one or other process. Some drugs are prepared from herbs, some from germs and animals, whereas some are manufactured in factories by chemical or biotechnical processes. Modes of drug administration vary – some are applied to skin and some taken orally. Injections of drug can be intradermal (in the skin), subcutaneous (under the skin) or intravenous (in a superficial vein). Some drugs are inhaled through nose or mouth (sprays/inhalers) and few others are administered by other routes.

Taking a tablet orally is usually safe, simple and cheap though it may not be completely absorbed in stomach or intestines. The absorbed drug is transported to liver where it is processed and transformed into an active compound. Some drugs can act without any processing in liver. An active drug then circulates through entire body. Though many drugs act at a particular organ, they do have effect on the entire body. A few drugs can gradually accumulate in body fat or the organs such as liver. A single dose of the drug remains active in body for some time (Biological half-life) and is then excreted out through urine or stools.

When a drug is injected the entire dose enters directly in circulating blood. It is not affected by digestive secretions in bowel and effects are quicker. Injected drug does not cause hyperacidity or other digestive disturbances.

Duration of drug activity in body can be increased with technological modifications in drug delivery. Such controlled release drugs (usually in the form of a capsule) alleviate need for multiple daily doses.

Dose of a drug depends on many factors such as type and severity of disease as well as age and weight of the patient. Efficacy of few drugs such as Methotrexate depends on hereditary factors too. Concomitant use of other drugs is also important as there can be interactions amongst them. Prolonged administration of certain drugs may necessitate increase of dosage in future. Use of some drugs such as opium-derivatives (used as pain killers and cough suppressants) can lead to addiction.