This section is from the book "A Text-Book Of Pharmacology, Therapeutics And Materia Medica", by T. Lauder Brunton. Also available from Amazon: A text-book of pharmacology, therapeutics and materia medica.
Ether introduced into the intestine greatly increases its vascularity. It also quickens absorption very much, as is shown by the fact that poison acts more quickly, and such substances as ferro-cyanide of potassium appear sooner in the urine, when they are administered along with ether than when given alone. Carbonic acid has a somewhat similar though weaker action.
Coto bark has been used in diarrhoea, and as it has no proper astringent action, its utility has been ascribed to an antiseptic action by which it diminished the formation of irritant products in the intestines. Albertoni has investigated the action of the coto alkaloids, and finds that although cotoine somewhat lessens putrefaction and the development of bacteria, it does not stop them either in the organism or outside it. It has, however, a very peculiar action on the vessels of the intestine. By keeping up artificial circulation in a loop of intestine (ride p. 382), he finds that cotoine dilates the arteries, causes the blood to flow more readily into the veins, and preserves the vitality of the intestine. It also dilates the vessels of the kidney, and causes the blood to flow more rapidly through them, but does not alter the circulation in the submaxillary gland.
Albertoni thinks that the benefit which cotoine produces in diarrhoea is due to dilatation of the intestinal vessels, and the increased power of absorption which it causes. He considers that in many cases of diarrhoea diminished absorption is a most important factor.1
Paracotoine acts like cotoine, but less strongly.
Opium and chloral also dilate the vessels of the intestine, but their action is a paralysing one, while that of cotoine is not.
It is possible that the beneficial action of bael fruit in dysentery may depend on some similar property, as this substance has the peculiarity of acting as a laxative in health, while it lessens the evacuations in dysentery.
Cholagogues probably influence absorption from the intestine powerfully (p. 406).
Intestinal Astringents. - Diarrhoea may depend (1) upon excessive peristaltic action, whereby the contents of the intestine are hurried along before time has been allowed for their absorption, (2) upon diminished absorption, (3) upon excessive secretion. In one form of diarrhoea, where the introduction of food into the stomach seems to excite peristaltic action throughout the intestine so that the person is frequently forced to rise from the table in order to evacuate the bowels, small doses of one half to two minims of liquor arsenicalis given immediately before meals, as recommended by Ringer, frequently act like a charm. In ordinary cases of diarrhoea, opium, by lessening the irritability of the intestine, is most serviceable. Some medicines lessen peristaltic action, not by affecting the bowel, but simply by removing the stimuli which were exciting it. Thus small doses of soda are useful in the diarrhoea of children by neutralising the acid which was acting as an irritant. Creasote has a similar action by lessening putrefaction or fermentation, and thus preventing the formation of irritant products. It' is probable that lime acts also to a certain extent by its antacid properties, but there is little doubt that there are other factors in its astringent action which we do not yet understand. The effect of cotoine on intestinal absorption has just been mentioned. With the view of ascertaining whether we could find any drug which would arrest the copious secretion from the intestine which takes place in cholera, Pye-Smith and I made a large number of experiments. For this purpose we isolated loops of intestine, and into one injected sulphate of magnesium mixed with the drug to be tested. In some experiments we injected the sulphate of magnesium into the intestine, and the drug which we wished to test into the veins.
1 Archiv fur exper. Path. und Pharm., vol. xvii. p. 291.
Sulphate of atropine, iodide of methyl-atropine, chloral-hydrate, emetine, morphine, sulphate of quinine, tannin, and sulphate of zinc, were all tried locally with negative results. Chloral and morphine injected subcutaneously also gave negative results.1
Fig. 140. - Diagram illustrating diarrhoea depending on the presence of scybala in the intestine. a is a scybalous mass; b is the fluid which it causes the intestine to secrete.
In many cases the best way of checking diarrhoea at its commencement is to give a purgative such as castor-oil, either alone or with a few drops of tincture of opium in it. The irritant substances which cause the diarrhoea are swept out of the intestine by the action of the purgative, and any irritation which remains is soothed by the opium. Chronic watery diarrhoea, alternating with constipation, is often best treated in the same way. We may suppose that here the presence of scybalous masses in the intestine gives rise to a watery discharge, which does not, however, wash away the scybala themselves (Fig. 140). When a purgative is given which causes secretion from the intestine above the scybala, the fluid in its downward flow, assisted also by the increased peristalsis, washes away the scybala, and thus removes the source of irritation.