The oil expressed from the seeds of Ricinus communis, of Calcutta. Castor oil contains several fatty acids, of which ricinoleic acid is peculiar to itself.
Externally castor oil is very soothing, and may be applied to the eye, or the surface, as a sedative and protective if perfectly pure.
Internally it is unirritating to the stomach, if pure, but if impure or rancid it may cause nausea and vomiting. Aside from this, the odor may provoke nausea even before the drug is swallowed, and all pains should be taken to avoid this possibility, by preparing it carefully and holding it at the side - not under the patient's nose - until the moment comes for swallowing it.
In the intestines it acts as a simple purgative, and here the oil which is not perfectly pure is more efficient. It is painless, with sedative and somewhat constipating after-effects.
The muscular coat and the glands of the intestines are stimulated, and evacuation results in from three to six hours - sometimes sooner.
It is not a hydragogue cathartic, as it does not appreciably increase the intestinal secretions. It does not act on the liver.
Ricinoleic acid enters the blood and tissues and is removed by all secretions, including the milk, and in this way purgation may be produced in a nursing infant.
Castor oil is very nauseous, and needs to be carefully administered, in order that it may be as little offensive as possible. To children it is best given in hot sweetened milk, and adults may take it well in this way; or it may be poured into the centre of an equal quantity of glycerin, or given in a little hot coffee, or in soda water, or in brandy; first wetting the sides of the glass, and pouring the oil carefully in the centre of 3 ss. brandy, then covering it with as much more. In all cases it will be more easily taken if the mouth be first rinsed out with brandy or peppermint, or any thing pungent which will blunt the sense of taste. A little carbonated water afterwards is gratefully received, or, to those who like olives, nothing is more acceptable after nauseating or bitter medicines than an olive, when it may be given.
Castor oil can be had put up in soft flexible capsules, which, though large, are easily swallowed.
Average dose, ℥ ss.-15 mils.
Dose for infant one year old, ʒ i.-4 mils.
The castor bean is very poisonous. The leaves have been used as a poultice, applied to the breasts to increase the flow of milk.