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chemotherapy(kē'mōthĕr`əpē), treatment of disease with chemicals or drugsdrugs,
substances used in medicine either externally or internally for curing, alleviating, or preventing a disease or deficiency. At the turn of the century only a few medically effective substances were widely used scientifically, among them ether, morphine, digitalis,
..... Click the link for more information. . One chemotherapeutic approach is the development of selectively toxic substances, i.e., substances that can destroy or inhibit infecting organisms or, as in cancer, malignant tissue, but do not damage normal host tissue. In treating infection, selectively toxic agents may block a biochemical reaction necessary to the viability of the pathogen but not to that of the host; for example, penicillinpenicillin,
any of a group of chemically similar substances obtained from molds of the genus Penicillium that were the first antibiotic agents to be used successfully in the treatment of bacterial infections in humans.
..... Click the link for more information. blocks synthesis of bacterial cell walls, a component animal cells lack. Other chemotherapeutic substances differentially affect biochemical reactions in different tissues; thus antimetabolites such as methotrexate and CytoxanCytoxan
, trade name for the drug cyclophosphamide, used to inhibit growth of tumors and rapidly proliferating cells. It is used in the treatment of leukemia, Hodgkin's disease, and lymphosarcoma and other solid tumors.
..... Click the link for more information. are more toxic to rapidly proliferating cells such as those associated with cancer than to normal cells. Other drugs act in various ways to produce effects that initiate or enhance some normal body function; for instance, neostigmine blocks the action of an enzyme limiting transmission of nerve impulses and thereby acts as a nervous system stimulant. The usefulness of chemotherapeutic agents also depends on their pharmacological action, e.g., their rate of absorption, rapidity of action and rate of excretion, degree of storage in the body, effects of products of their metabolic breakdown, and potential for causing hypersensitivityhypersensitivity,
heightened response in a body tissue to an antigen or foreign substance. The body normally responds to an antigen by producing specific antibodies against it. The antibodies impart immunity for any later exposure to that antigen.
..... Click the link for more information. reactions. Some drugs are given prophylactically, to prevent infection, e.g., penicillin is given to rheumatic fever patients to prevent reinfection by the causative organism, the streptococcal bacterium.
the use of drugs to act on the causative agents of infectious and parasitic diseases and on tumor cells. The treatment of disease by chemical agents was first practiced early in the 20th century, after P. Ehrlich demonstrated the directed synthesis of agents capable of acting on microorganisms. Ehrlich used salvarsan (the first potent agent in chemotherapy) in 1909 and established the principal mechanisms of the specific action of chemical agents.
REFERENCESEhrlich, P. Materialy k ucheniiu o khimioterapii. St. Petersburg, 1911. (Translated from German.)
Khimioterapiia infektsionnykh boleznei (collection of articles). Moscow, 1958.
Strategiia khimioterapii. Moscow, 1960. (Translated from English.)
Larionov, L. F. Khimioterapiia zlokachestvennykh opukholei. Moscow, 1962.
Votchal, B. E. Ocherki klinicheskoi farmakologii, 2nd ed. Moscow, 1965.
Kassirskii, I. A., and Iu. L. Milevskaia. Ocherki sovremennoi klinicheskoi terapii, 2nd ed. Tashkent, 1970.