Pommades, Onguents, Fr.; Salben, G.; Pomatas, Unguentos. It.; Pomadas, Unguentos, Sp.
These are fatty substances, softer than cerates, of a consistence like that of butter, and such that they may be readily applied to the skin by inunction. When ointments are prepared by merely mixing medicinal substances with simple ointment, hydrous wool-fat, lard, or petrolatum, care should be taken, if the added substance be a powder, that it be brought to the finest possible state of division before being incorporated with the unctuous matter. If soluble in water or in alcohol, it may often be advantageously rubbed with a little of one of these liquids. Gritty matter should not be allowed to enter these preparations. When an extract is added, if not uniformly soft, it should be made so by trituration with water or alcohol, according to its nature. Many of the ointments become rancid if long kept, and should, therefore, be prepared in small quantities at a time, or only when wanted for use. The tendency to rancidity may be in a considerable degree counteracted by imbuing the unctuous vehicle with benzoin, or with poplar buds, as recommended by Deschamps (A. J. P., xv, 260); but care should be taken that there be no therapeutic objection to the admixture. Elm bark is said to have the same effect. According, to Geisler, ten drops of spirit of nitrous ether, incorporated with an ounce of ointment, will overcome the disagreeable fatty odor. (Ph. Ch., 1847, 927.) Hydrous wool-fat or lanolin, petrolatum, and glycerite of starch are now used as vehicles for ointments. In the selection of a vehicle for an ointment it is important to consider the object for which the ointment is to be used. Lanolin is a natural emollient of the skin, composed of cholesterin and other substances.
Glycelceum is an oleaginous compound of finely powdered almond meal 1 part, glycerin 2 parts, and olive oil 6 parts. It was proposed by T. B. Groves, C. D., Sept. 14, 1867, as a substitute for plasma and other fatty bodies, and has no doubt advantages, one of which is the facility with which it can be removed from the skin by a wet sponge. It has been proposed to substitute glycerin for oils and fats in the preparation of ointments, either wholly or in part; but ointments thus prepared are altogether unfit for application by inunction, as a portion of the glycerin remains upon the skin, producing a rough sensation of adhesiveness, very different from the softness caused by oleaginous matter, and in some skin diseases glycerin in an ointment would be positively injurious.
The cerates having been abolished as a class in the British Pharmacopoeia, a few of the individual articles have been transferred to the ointments, making the definition of the latter class of preparations, as given above, not exactly applicable to all the individual substances at present included among them in that Pharmacopoeia. We consider no substance to be strictly entitled to the name of ointment which is not of such a consistence as to adapt it to application to the skin by friction or inunction. Ointments should be dispensed in glass, porcelain, or queensware pots or jars, or, if for temporary use, in tight wooden boxes. We have used a very convenient method of dispensing soft ointments by introducing them into compressible tubes. These tubes are similar to those used for holding artists' colors, and have the advantage of shielding the ointment from the oxidizing action of the air while allowing the use of the desired quantity. Vanderkleed and Heidlberg (Proc. P. P. A., 1913, p. 312) state that the only satisfactory method of determining whether or not the proper degree of subdivision has been attained is by the use of the microscope, and call attention to some of the precautionary measures which should be taken in order to obtain correct results. Their article is illustrated by numerous photographic representations of ointments of different degrees of fineness. For a classification of ointments in accordance with their therapeutic use, by C. S. N. Hallberg, see West. Drug., 1900, 652.
Uses.—Ointments are used either for their local effects upon the skin or as a means of introducing drugs into the system through endermic absorption. The effects of fat-like substances upon the skin are due in part to their softening or emollient properties, and in part to the protection of the epiderm from the air, bacteria, or friction; they may also serve as carriers of antiseptic or other medicaments which influence pathological conditions of the skin. It is manifest that different qualities for an ointment base are desirable according to the purpose for which it is intended. Thus if it is intended to protect the skin the choice should fall on a substance which is not irritant nor readily absorbed nor liable to become liquid at a body temperature. On the other hand, for endermic administration one should choose a base which easily penetrates the skin. Concerning this last factor there has been a considerable amount of experimental investigation with not altogether harmonious results. The most widely used method has been to rub into the skin ointments made with various bases containing some substance easily demonstrable in the urine, and then determining the proportion of the medicament eliminated. Hirschfeld and Pollio (Arch. f. Derm. u. Syph., 1904, lxxii, p. 163) found that the iodides were absorbed readily in ointments made with petrolatum or lard, but almost not at all from ointments made from wool fat. Bourjet (Th. M., 1893) found that salicylic acid was absorbed readily from ointments made with true fats but poorly in those made with petrolatum or glycerin as the base. Sauerland (Biochem. Zeit., 1912, xl, p. 56) in an elaborate research found that with vaseline, 40 per cent., with lard, 26 per cent., and with wool-fat. 18 per cent. of the iodine of iothion was absorbed through the skin; likewise methyl salicylate was absorbed in the same order, although in much smaller proportions. On the other hand, spirosal, a glycol salicylate, was absorbed scarcely at all from a lard ointment, but in fair amounts from either wool-fat or vaseline. Gardiner (B. M. J., 1912, i, p. 238) rubbed ointments containing various stains into the shaven skin of guinea pigs and then examined the skin microscopically to observe the depth of penetration. He found that olive oil penetrated more deeply than any substance with which he experimented, but that goose grease and lard also penetrated well. Petrolatum remained limited to the very superficial portions of the skin. Wool-fat, while it penetrated somewhat more deeply than petrolatum, was noticeably behind lard. Wild (B. M. J., 1911, ii, p. 161) employed a very different method to study this subject. He rubbed pure ointment bases into the skin for a measured time and then scraped off what was left on the skin and weighed. The difference between the quantity taken and that recovered he considered to represent the amount absorbed. He found that petrolatum was absorbed practically not at all, that of lard or olive oil about 15 per cent., and of hydrous wool-fat about 20 per cent., but that the absorption of the latter was noticeably less if it was deficient in water. While the evidence quoted is somewhat contradictory and it is probable that some ointment bases are better for one drug and some for another, yet it seems to us that in a general way the conclusion is justified that where absorption is desired lard is probably the best of the official ointment bases.