ABSTRACT
Administration of the drug by any route that does not involve direct introduction into the systemic circulation is called extravascular drug administration. This includes intramuscular, subcutaneous, intradermal, oral, buccal, sublingual, rectal, intranasal, pulmonary, transdermal, ocular, and other routes. The oral route is the most common route of extravascular drug administration because it is the most convenient route, especially when the drug has to be administered repeatedly. Some drugs are administered orally for their local effect in the gastrointestinal tract (GIT) such as in the treatment of hyperacidity or GIT infections. In this case, the drug does not have to be absorbed from the GIT. However, the majority of the drugs administered orally are intended to produce a systemic effect such as to relieve pain, to control blood pressure, or to lower blood sugar, etc. Drugs administered to produce a systemic effect have to be absorbed from the site of administration to the systemic circulation and then distributed to all parts of the body to produce their therapeutic effects.
