This section is from the book "Materia Medica: Pharmacology: Therapeutics Prescription Writing For Students and Practitioners", by Walter A. Bastedo. Also available from Amazon: Materia Medica: Pharmacology: Therapeutics: Prescription Writing for Students and Practitioners.
1. Olive oil (oleum olivae) is essentially a nutritive and digestible fat. However, in amounts of one or two tablespoonfuls it may have a mildly laxative action, being changed to soap and glycerin in the intestine. In large amounts, as 1/4 pint (240 c.c.), it is only partly saponified, and gets some of its laxative power from increasing the bulk of the intestinal contents. It had at one time a reputation for the cure of cholelithiasis; but as a solvent for gall-stones in the gall-bladder it has no value whatever. In the larger amounts it tends to form soap-lumps which have not infrequently been mistaken for gall-stones in the feces. It distinctly prolongs the emptying time of the stomach.
Olive oil is also given by mouth as a demulcent to diminish excessive hydrochloric acid secretion in the stomach, especially in ulcer, and by rectum to allay irritation, as in proctitis and hemorrhoids. Warm oil is often employed by rectum to soften hard feces, but Hertz found that oil does not penetrate the lumps of feces, and that these are much more readily softened by water.
2. Castile soap (sapo) is nearly pure sodium oleate. It is mildly irritant to mucous membranes, hence is laxative. Soapsuds enemata may be made of Castile soap, or if a stronger action is desired, of laundry soap, which contains free alkali and is more irritating.
3. Glycerin (glycerinum), though slightly laxative when administered by mouth, is chiefly used in the form of the glycerin suppository (suppositorium glycerini), or as a mildly irritating addition to an ordinary enema. Hertz says it is irritant to the mucous membrane of the anal canal, but not to that of the rectum.
4. Castor Oil (Oleum Ricini), This oil is saponified in the small intestine to form glycerin and sodium ricinoleate, a soap which is much more irritant than Castile soap to the intestinal mucous membrane. Its great advantages are its rapidity of action, its thoroughness, its comparative freedom from irritative griping, and its harmlessness if catharsis does not result. A dose of one-half to one ounce (15-30 c.c.) usually produces one or more copious soft or watery stools in from two to six hours. In some of our cases over a quart of stool was recovered after one ounce of castor oil. It has little if any tendency to produce inflammation, hence is not a drastic cathartic; but it is a powerful stimulant of peristalsis. This effect is dependent on the formation of the soap, for castor oil unsaponified is bland and non-irritant. If used by rectum, it should be saponified with an alkali, otherwise it acts like olive oil. In Rowntree's experiments, 25 c.c. by hypodermatoclysis had no effect upon the bowels, and merely caused a painful swelling at the site of the injection. Administration
Various methods of administration have been devised to hide the nauseating taste. The prepared oils usually contain saccharin and some aromatic such as peppermint. The three-layer or "sandwich" method in which the oil is suspended between two layers of watery or alcoholic liquid, is the favorite. For this purpose compound tincture of cardamom, spirit of peppermint, whisky, orange-juice, lemon-juice, lemonade, ice-water or beer may be employed. Glycerin is sometimes used for the lower layer. The layers should not be stirred together. The favorite drug-store method is to place some syrup of sar-saparilla in a glass and then cause it to foam by carbonic water from the soda fountain, or by a little tartaric acid and sodium bicarbonate. Then the oil is poured in without allowing any to get on the edge of the tumbler. The mixture must not be stirred. The oil floats between some of the syrup below and the foam above, and the whole is drunk without stopping. The oil is not tasted at all. The principle of these methods is to have the mouth and tongue wetted with a liquid (the top layer) upon which the oil will readily slip down. If any oil sticks to the tongue, the taste will .be perceived, though it is stated that vichy-lemonade following the dose will prevent this. For infants and children, an emulsion made with acacia and a flavored syrup may be employed. There are some powdered castor oils on the market, such as risiccol and castor-lax, made by absorbing castor oil with magnesia. To get a full castor-oil action they must be taken in very large dose, 2 ounces (60 gm.).
Castor oil is extensively employed in dose of 1 ounce (30 c.c.) as an occasional brisk cathartic for the thorough cleansing of the intestines. This may be desired in fermentative diarrhea, food or ptomain-poisoning, intestinal flatulency, or mucous colitis, or because of continued colonic stasis. Such thorough catharsis is prone to be followed by constipation for a day or two during the refilling of the stagnant bowel. Castor oil in cathartic amounts is not suited for daily repetition. By its activity it tends to congest and stimulate the female pelvic organs, hence must not be employed as a cathartic during menstruation or pregnancy, though it is sometimes administered to bring on labor pains at full term. In colitis and intestinal putrefaction a favorite treatment is a capsule containing 2 1/2 minims (0.15 c.c.) of castor oil and 2 1/2 grains (0.15 gm.) of salol, or twice these amounts, three or four times a day. The effect of such small amounts of the oil is problematic.
Fig. 3. - The abdomen of this patient was greatly distended with gas, which seemed as if in his stomach, though unrelieved by belching. After a rectal injection of bismuth this x-ray picture was taken, the patient being in the standing position. The light areas in the bowel are gas. (Picture taken by Dr. L. T. LeWald.)
Fig. 4. - The same patient as in Fig. 3. This x-ray picture was taken after free movements of the bowels by castor oil. There was complete relief from flatulency. (Picture taken by Dr. L. T. LeWald.)