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(or drug therapy), the treatment of disease by drugs.
In etiotropic pharmacotherapy the drug employed acts on the cause of the disease; an example of etiotropic therapy is the treatment of infections by antibiotics or of poisoning by specific antidotes. Related to etiotropic pharmacotherapy is replacement pharmacotherapy, in which drugs introduced into the organism replace the deficient physiologically active substances; examples are the use of hormones in cases of insufficient endocrine gland function and the use of vitamin B12 in pernicious anemia. Pharmacotherapy is pathogenetic when the drug acts on the mechanism of development, or the pathogenesis, of the disease; for example, the use of cardiac glycosides in cardiac insufficiency, of nitroglycerin in angina pectoris, and of epinephrine in bronchial asthma is pathogenetic therapy. If only the symptoms of the disease are relieved by the drugs, as when analgesics or cough suppressants are used, the pharmacotherapy is called symptomatic therapy.
Pharmacotherapy is frequently combined with other treatment methods, such as physical therapy and dietotherapy. Drugs are often used in various combinations. The choice of a particular drug is determined by such factors as the nature of the disease, the course of the disease, and the patient’s tolerance of the drug; the drug must possess maximum efficacy and produce minimum side effects.
A distinct branch of pharmacotherapy is chemotherapy of infectious diseases and tumors. Chemotherapeutic agents have a selective and specific action on the causative agents (protozoans, microbes, and viruses) or on the substrate (tumor cells) of the disease. This selective therapeutic action depends on the specific physiological, biochemical, and other characteristics of the infective agent or tumor cell. For example, penicillin selectively damages the surface membrane of a bacterium, causing an excessive amount of water to enter the microorganism and to kill it (bactericidal action). Sulfanilamides disrupt protein synthesis and thereby slow the multiplication of microorganisms (bacteriostatic action). An important principle of chemotherapy is that the drug dose must be of sufficient strength and must be administered at appropriate intervals to maintain the necessary drug concentration in the blood and tissues. The efficacy of antimicrobial therapy is judged by the dynamics of the symptoms of the disease (for example, by the lowering of the body temperature and the normalization of the blood composition), and the efficacy of antitumor therapy, by the disappearance of tumor cells.
The therapeutic effect of a drug varies with the mode of administration and the ability of the drug to cross tissue barriers and to accumulate in the affected areas. Since in the course of therapy some microorganisms or tumor cells may become resistant to a given drug and may multiply, several drugs are often used in combination to achieve a more complete antimicrobial or antitumor effect; for example, penicillin may be combined with streptomycin, or a combination of cytostatic agents may be directed against tumor tissues that vary in metabolism and rate of division. The use of antibiotics and sulfanilamides has been responsible for the control of such infectious diseases as tuberculosis, pneumonia, and scarlet fever. Modern combinations of cytostatic agents can sharply increase the life-span of patients with Hodgkin’s disease or with certain other cancers and can sometimes effect a virtual cure. Intensive research is being conducted toward the development of antiviral chemical preparations.
Pharmacotherapeutic agents may produce undesirable side effects. The side effects may be due in some cases to the patient’s intolerance to the drug or to allergic reactions; in other cases they may be due to the toxic effect of large doses of the drugs, as in cytotoxic disease. Modern pharmacotherapy, which includes the use of psychotropics, chemicotherapeutic and hormonal preparations, and numerous other effective drugs, enables the physician to intervene in the course of a disease.
REFERENCESVotchal, B. E. Ocherki klinicheskoi farmakologii, 2nd ed. Moscow, 1965.
Kassirskii, I. A., and Iu. L. Milevskaia. Ocherki sovremennoi klinicheskoi terapii, 2nd ed. Tashkent, 1970.
Mashkovskii, M. D. Lekarstvennye sredstva, 7th ed., parts 1–2. Moscow, 1972.
Trinus, F. P. Farmakoterapevticheskii spravochnik. Kiev, 1972.
Lekarstvennaia bolezn’. Sofia, 1973. (Translated from Bulgarian.)
M. D. MASHKOVSKII and A. I. VOROB’EV