Antidiarrhoeals

ANTIDIARRHOICA (from Greek anti against and diarrhoia diarrhea), remedies that eliminate factors contributing to the onset of diarrhea. Depending on the factors causing diarrhea, several groups of antidiarrheals are distinguished that act on the motor apparatus of the intestine; these include: a) substances that depress the motor nerve of the intestine—the vagus nerve (for example, atropine, which paralyzes its endings); b) substances that stimulate the inhibitory nerve of the intestine—the splanchnic nerve (for example, adrenaline, which stimulates its endings, and morphine, which increases the tone of its center); c) substances that depress local intestinal reflexes (for example, morphine); d) substances that depress intestinal musculature (for example, papaverine). To this same group can be attributed e) substances that protect the intestinal mucosa from mechanical and chemical irritants that cause a reflex increase in peristalsis (astringents and enveloping substances, as well as indifferent powdery substances such as talc, white clay, and animal charcoal). Finally, f) medications that act on etiological factors; for example, in increased hormonal activity of the thyroid gland (thyreogenic diarrheas), the rational treatment of this diarrhea is the elimination of hyperthyroidism. The next group of antidiarrheals includes substances capable of lowering the secretory activity of the intestinal glands (these antidiarrheals also act as anti-inflammatories). Such substances are astringents (vegetable-origin tannins and certain metal salts) which, by precipitating mucin and intercellular protein, form a film on the intestinal surface that limits mucus secretion and protects the mucosa from harmful effects. Calcium preparations (for example, calcium carbonate and lime water) must be specially mentioned, which also possess the ability to reduce the permeability of the vascular wall and thereby limit transudation; in addition, they increase the excitability of the inhibitory apparatus of the intestine. Morphine and partly atropine also belong here. In case of impaired absorption processes, antidiarrheals can play the role of substitution therapy; for example, in impaired gastric digestion (gastrogenic diarrheas)—hydrochloric acid (in the case of achylia gastrica) together with pepsin, etc. In the event that diarrhea is caused by infectious agents, antiseptic agents—salol, menthol, benzonaphthol, and others—can play a known role as antidiarrhoeica. Etiotropic agents also belong to this group: quinine in amebic dysentery and balantidiasis, therapeutic serum and vaccine in bacillary dysentery, and so on. In diarrheas of helminthic diseases, anthelmintics will play the role of antidiarrheals. Since complete disinfection of the intestine is unattainable, in practice they strive to achieve a reduction in the bacterial flora of the intestine by the administration of laxatives. Among the latter, some are also ascribed disinfecting properties along with properties to stimulate intestinal secretion (calomel); this achieves a certain liberation of the intestinal wall from infectious agents. For the purpose of removing various chemical noxious substances and poorly digestible food that can in a number of cases, due to mechanical and chemical irritations, cause diarrhea, the laxative least irritating to the intestine is most frequently used—castor oil. For the purpose of adsorption of bacterial bodies and their toxins, animal charcoal is used with the subsequent administration of a laxative. If the majority of the considered antidiarrheals coincide in their mechanism of action with obstipantia, the substances used for the purpose of disinfection and cleansing of the intestine, as well as for substitution therapy (in case of impaired digestive chemistry) do not present this coincidence.

V. Karasik.