This section is from the book "Materia Medica Pharmacy, Pharmacology And Therapeutics", by W. Hale White. Also available from Amazon: Materia Medica Pharmacy, Pharmacology And Therapeutics..
A fixed oil expressed from the seed of Ricinus communis Linne (nat. ord. Euphorbiaceae).
A pale yellowish or almost colorless, transparent, viscid liquid, having a faint, mild odor, and a bland, afterwards slightly acrid, and generally offensive taste. Sp. gr., 0.950 to 0.970.
In an equal volume of Alcohol, and, in all proportions, in absolute Alcohol, or in glacial Acetic Acid; also soluble in 3 times its volume of a mixture of 19 volumes of Alcohol and 1 volume of water (absence of more than about 5 per cent. of most other fixed oils).
The chief constituents are - (1) Ricinolein, C3H5(C18H34 O3)3, which is the Ricinoleic Acid (C18H34O3), Glyceride. This constitutes the chief bulk. (2) Other fixed oils, as palmitin, stearin, etc. (3) Possibly an alkaloid, Ricinine, not purgative. (4) According to some authorities an active principle which has not yet been isolated.
Dose, 1/4 to 2 fl. oz.; 8. to 60. c.c.
Castor oil seeds are not official, but it is important to recognize them. They are 17 mm. long and 8 mm. wide, ovoid, flattened. The seed is prolonged into a sharp beak. Epidermis shiny gray, marked by brownish bands and spots. Kernel white. They contain 50 per cent of the oil, and an acrid substance which makes them poisonous. Three Castor oil seeds have been known to kill an adult man. Quite likely the seeds are not poisonous when matured.
Castor oil is, like olive oil, protective and sedative, and may be used to drop into the eye when the conjunctiva is inflamed, and as a solvent for homatropine, but this solution is occasionally a little irritating.
Gastro-intestinal tract. - The so-called unpleasant taste of castor oil is mostly due to the smell, and is not noticed much if the nose is held when the oil is drunk. Medicinal doses produce no effect on the stomach. Reaching the intestine the oil is an excellent simple laxative or mild purgative, acting in about five hours, and causing no griping nor subsequent constipation. The motion is soft, but not liquid. Castor oil will purge even when rubbed into the skin. How it acts is unknown but it is said to stimulate unstriped muscular fibre whenever found. It has been thought that the ricinolein (ricinoleic acid glyceride) in the oil is decomposed in the duodenum, and the ricinoleic acid purges, but this is probably incorrect. The most likely view is that the oil contains some purgative principle which has not yet been isolated. Probably the seeds contain much more of this than the oil, for they are ten times more purgative, a fact which it is impossible to explain if it is the ricinoleic acid which purges. Castor oil will purge when given per rectum.
Mammary glands. - The leaves applied locally to the breasts are said to be galactagogue.
Castor oil is perhaps the best simple purgative we have, and is very useful in cases in which there is slight temporary constipation. Being mild in its action it is very suitable for getting rid of undigested food that is causing diarrhoea, and a dose of castor oil with a minute quantity of laudanum in it is a favorite remedy for certain forms of diarrhoea. It is also especially convenient in pregnancy, after delivery, and when in any abdominal disease, as typhoid fever, peritonitis, or when, after abdominal operations, the irritation caused by the faeces makes it absolutely necessary to get the bowels open. Also, it is very useful for children, or for very old or infirm persons, or for those suffering from piles or fissures. It is a good purgative to give before and after the use of anthelmintics aspidium being excepted. It should not be given during the later months of pregnancy owing to its action on unstriped muscle fibres.
Its nauseous taste is the only objection to it. As already mentioned, this can largely be overcome by holding the nose, and there are many forms of castor oil in the market so prepared as to be almost colorless and odorless. It may be taken in capsules, but they are bulky. Lemon juice or coffee conceals the taste to some extent, or the oil may be added to a teaspoonful 4. c.c. of peppermint water, and then a little brandy added till the oil neither sinks nor floats. If the inside and rim of the glass are moistened with the vehicle, the oil, which should, if possible, be between two layers of the vehicle, is hardly tasted. It is best administered in the beverage known as sarsaparilla.
As an enema (castor oil, 1; warm olive oil, 5; mixed thor-roughly) it is useful when a mild injection is required.
Breasts. - The leaves of the castor-oil plant applied to the breasts will sometimes induce the secretion of milk. A fluid extract of them not official may also be taken three or four times a day.