To be effective, the majority of drugs must be absorbed into the blood stream. in order to reach the site where their effects needed. the method of administering a drug determines the the route it takes to get into the blood stream and the speed at which it is absorbed into the blood. When a drug is meant to enter the blood stream it is usually administered in one of the following ways: through the mouth or rectum, by injection, or inhalation. drugs implanted under the skin or enclosed in a skin patch also enter the blood stream.
When it is unnecessary or undesirable for a drug to enter the blood stream in a large amounts, it may applied topically so that its effect is limited mainly to the site of disorder, such as the surface of the skin or the mucous membranes (the membranes of the nose, eyes, ears and mouth, vagina, and rectum). Drugs are administered topically in a variety of preparations, including creams, sprays,drops, and suppositories. most inhaled drugs also have a local effect.
Administration By Mouth
Giving drugs by mouth is the most frequently used of method of administration, most drug that are given by mouth are absorbed into the blood stream through the walls of the intestine. the speed at which the drugs are absorbed and the amouth of active drug that is available for used depend on several factors, including the form in which it is given( for example, as a tablet or a liquid) and whether it is taken with food or an empty stomach, if a drug is taken when the stomach is empty (before meals, for example), it may act quickly than a drug that is taken when the stomach is full. some drugs (like antacids, which neutralized stomach acidity) are taken by mouth to produce a direct effect on the stomach or digestive tract.
Tablet are available which are placed in the mouth but not swallowed. they absorbed quickly into the blood stream through the lining of the mouth, which has a rich supply of blood vessels. both sublingual and buccal tablets acts in this way. Sublingual tables are placed on the pouch between the cheek and the teeth.
Drugs intended to have a systematic effect may be given in the form of suppositories inserted into the rectum, from whence they are absorbed into the blood stream. this method may be used to give drugs that might be destroyed by the stomach in digestive juices. it is also people who cannot take medication by mouth, such as those suffering from nausea and vomiting. drugs may also be given rectally for local effect, either as supportive ( to relieves hemorrhoids) or as enemas( for ulcerative and colitis)
Drugs may be inhaled to produce a systematic effect or a direct local effect on the respiratory tract. Gases to produce general anesthesia are administered by inhalation and are absorbed into the blood stream through the lungs, producing a general effect on the body. Bronchitis, used to treat certain types of astma, emphysema and bronchitis, are a common example of drugs administered by inhalation for there direct effect on the respiratory tract, although some of the active drug also reaches the blood stream.
Administration By Injection
Drugs may be injected into the body to produce systematic effect. one reason for injecting drugs is the rapid response that follows. other circumstances which call for injection: a person intolerance to drug when taken by mouth; a drug inability to resist inactivation by stomach acid(Insulin is an example) the inability of the drug to pass through the intestinal walls into the blood stream. drug injection may also be given to produce a local effect, as is often done to relieve the pain of arthritis. the main types of injection are intramuscular, intravenous, and subcutaneous.
In treating localized and disorders such as skin infection nasal congestion, it is often preferable when a choice is available to prescribe drugs in a form that has topical rather than a systematic effect. the reason is that it is much easier to control the effects of drugs administered locally and to ensure that they produce the maximum benefit with a minimum side effects.
Topical preparations are available in a variety of forms, from skin creams, ointment lotion to vaginal suppositories, nasal spray and ear and eye drops. it is important when using topical preparation to follow instruction carefully, avoiding a higher dose than recommended or application for longer than necessary. this will help avoid adverse systematic effects caused by the absorption of larger amounts into the bloodstream.