(Route of Administration.) How a drug or therapy is introduced into the body. Systemic administration means that the drug goes throughout the body (usually carried in the bloodstream), and includes oral (by mouth), intravenous (injection into the vein, IV), intramuscular (injection into a muscle, IM), intrathecal (into the spinal canal), subcutaneous (beneath the skin, SQ), and rectal administrations. Local administration means that the drug is applied or introduced into the specific area affected by the disease, such as application directly onto the affected skin surface (topical administration). The effects of most therapies depend upon the ability of the drug to reach the affected area, thus the route of administration and consequent distribution of a drug in the body are important determinants of its effectiveness.