Drugs are chemical substances which affect living organisms. Such substances, also known as medicines, aare used to detect, cure and prevent diseases, and relieve symptoms. Many drugs are synthetic forms of naturally occurring substances, that is, chemical copies of the original. Some are obtained from botanical or animal sources, for example, belladonna used for some gastrointestinal problems is derived from the deadly night shade; opiate drugs including morphine are derived from certain types of poppy. Many vaccines, thyroid hormones and insulin (until recently) are obtained from animal sources. Some hormones are produced in the laboratories. The process involves altering certain micro-organisms at the genetic level and thereby changing the products of cell activity. For instance, the hormone insulin which is produced naturally by humans can now be manufactured by genetically-engineered bacteria. Most drugs are produced by pharmaceutical companies through chemical processes. They are marketed only after testing for safety and efficacy. Testing is done on animals and human volunteers. Drugs cannot be marketed without the approval of the Food and Drug Administration (FDA), also called the Drug Controller/Commissioner in some states. The highest drug control authority in India is the Drug Controller of India.

Drug Forms and Administration

Drugs are available to be administered (that is, dispensed) in the human body in various forms: as tablets, capsules, liquids (for example syrups, drops), injection solutions, topical creams (ointments), suppositories and pessaries, eye and ear drops, nasal drops and sprays and inhalers. These forms are specially designed for the needs of administration and to ensure correct dosage. Sometimes colouring and flavouring and other inactive ingredients are added to the drug. These ingredients are added to improve the chemical stability and to extend efficacy of the drug for a longer period of time.

Let us look at some of the available forms of drugs (see also the box below on efficacy of various dosage forms).

Tablet: The drug is compressed in a solid form, mostly round in shape. Other ingredients are added to it like diluents (sucrose, lactose, sodium chloride), binders (acacia, gelatin, glucose), granulating agents (gum, water, starch pastes), lubricants (magnesium stearate, purified talc) or disintegrating agents (starch, sodium bicarbonate, tartaric acid). Tablets are the cheapest form of medicines.

Capsule: A capsule is a gelatin shell in cylindrical shape containing the drug. The shell breaks open when swallowed. Slow-release capsules contain pellets, which dissolve in the gastrointestinal tract.

Slow-release or controlled release capsules/tablets are dosage forms that release medication over extended time periods to avoid high concentrations in the digestive tract or to provide longer duration of action than are available through conventional dosage forms. Some abbreviations used normally here are: LA (Long Acting); SA (Sustained Action); SR (Sustained Release); TR (Time Release); ER (Extended Release).

Liquids: Many drugs in liquid form may have its active ingredients combined in a solution, suspension or emulsion with other inactive substances such as solvents, preservatives, flavouring and colouring agents. Different forms of liquids include mixture, elixir, emulsion or syrup:

-		a mixture contains one or more drugs either dissolved to form a solution or suspended in a liquid.
-		an elixir is a solution of drug in sweetened mixture of alcohol and water and is often flavoured.
-		an emulsion is a drug dispersed in oil and water. An emulsifying agent is included to stabilise the
		product.
-		a syrup is a concentrated solution of sugar containing the active drug with flavouring, colouring and
		stabilising agent (s).

Tablets, capsules and liquids are administered to the patient by mouth.

Topical skin preparations are only for external use. They are applied on the skin. They include:

-		cream which is non-greasy and is used to apply drugs to the skin, to cool or moisten the skin.
-		ointment which is greasy preparation used to apply drugs or act as protective or lubricant layer for
		the relief of dry skin conditions.
-		lotion which is a solution or suspension applied to unbroken skin.

Injectable solutions (or injectables) are sterile preparations of a drug dissolved or suspended in a liquid. Many injectable drugs are packed in sterile disposable syringes to avoid contamination. Some are available in multiple dose vials. They may be administered intramuscularly (through muscle tissue), intravenously (through veins) or subcutaneously (through the skin). Injections can also be intra-articular (injection made within a joint), intrathecal (injection made within the spinal canal), intravascular (within a vessel or vessels), etc. For a more listing see: http://www.dlis.dla.mil/fiigdata/A4510/chart2.html