Glycerin, Glycerol.

A liquid composed most largely of a trihydric alcohol (C3H5(OH)3) obtained by the processes of hydrolysis and distillation of fats, both animal and vegetable, or of fixed oils.

Description.—A thick, syrupy, colorless liquid having a sweet and warming taste and a faint but agreeable odor. It has a great avidity for moisture, becoming appreciably thinner upon long exposure to the atmosphere. It mixes with water or alcohol; and is insoluble in ether, chloroform, and fixed and essential oils. Dose, ½ to 2 fluidrachms.
Preparation.—Suppositoria Glycerini, Suppositories of Glycerin.

Action.—Glycerin is a powerful hygroscopic. So great is its avidity for water that it will readily abstract moisture from the tissues to which it is applied. It is also slightly irritant to the skin and mucous surfaces, and considerably so to abraded surfaces. The discomfort quickly subsides, however, and it then acts as an antiseptic and protective emollient to the skin. It is a demulcent to mucous tissues. Applied to the rectum it provokes evacuation, both by its irritating and dehydrating effects. Glycerin kills parasites, both cutaneous and intestinal, and allays itching, probably by its protective, antiseptic, and hygroscopic powers. Glycerin is rapidly absorbed by the intestines and is mostly oxidized in the body. By some it is thought to be, in some measure at least, a food, and indirectly a conservator of fats through its effects of increasing the non-nitrogenous reserve of the body. It is also believed to increase energy. Upon the glycogenic function its effects are still in doubt, many contending that it reduces the sugar when in excess in the body. Glycerin is laxative and in very large amounts acts not unlike alcohol, producing a similar intoxication and like gastric effects. It is also said to favor the elimination of uric acid.

Therapy.—External. The bland and practically unirritating character of pure glycerin, in the presence of a little water, its permanence when exposed to the air (except absorption of moisture), and the completeness with which it shields the parts make it the most largely used external application in a great variety of local disorders. Its protective unctuousness without being greasy, its splendid and extensive solvent powers, its ability to hold in close contact to the tissues powders and other medicines that would dry and fall off if applied with alcohol or water, its antiseptic and emollient properties, and its antipruritic qualities, make it an indispensable vehicle. It is freely miscible with water and most ointment bases, and dissolves or holds in suspension the most commonly used external medicines. It should never be applied full strength, however, except where its dehydrating effects chiefly are desired. Through its great greed for water it readily removes moisture from the tissues, leaving them hardened and more likely to crack. A little water should be added to it for local use, or the parts may be moistened and left wet before its application. Only pure glycerin should be used.

Equal parts of glycerin and water, or preferably rose water, form an elegant and emollient cosmetic lotion for chapped hands, lips, and face cracked or sore nipples, excoriated and chafed surfaces, and swollen hemorrhoids. A few grains of borax sometimes add to its efficiency. Compound tincture of benzoin and glycerin is also a pleasant application. For those exposed to winds and storms, and who have their hands much in water, the following is splendidly effective: Rx Glycerin, 2 fluidounces; Carbolic Acid, 10 grains; Tincture of Arnica Flowers, ½ fluidounce; Rose Water, enough to make 4 fluidounces. Mix. Sig.: Apply after thoroughly washing and rinsing the hands, and while they are still wet. Sometimes lobelia may be used in place of the arnica.

Glycerin, added to poultices, renders them soothing and keeps them moist. It forms a good application to boils, carbuncles, small abscesses, and to local edemas, as of the prepuce. Here it may be used pure for its antiseptic and dehydrating effects. Mixed with alcohol (1 part), glycerin (3 parts), it makes a useful and "drawing" application for boils, and an antiseptic stimulant for foul ulcerations. A mixture of glycerin and water in proportions to suit the case may be used as a toilet wash for the mouth in fevers, to keep the tongue and lips soft and pliable, and to remove sordes and other viscous secretions. It also reduces the thirst occasioned by the dryness of the mouth.

Glycerin may be used as a vehicle for lime water for application to small burns, erythema, and slight excoriations; for menthol for the relief of itching in urticaria, chronic eczema, and other pruritic conditions; for boric acid in the mild forms of facial dermatitis; for lactic acid in freckles, sunburn, and other pigmentations; for bismuth, borax, salicylic acid, phenol, boric acid, or sodium or potassium bicarbonate when their long-continued local effects are desired, especially in ulcerations and various skin diseases. A small portion of liquor potassae (½ per cent) may be added to it for use upon rough skin and in chronic eczema. Among the skin disorders in which it is especially useful as a vehicle may be mentioned impetigo, lichen, porrigo, psoriasis, pityriasis, herpes, and tinea versicolor (with mercuric chloride) and other parasitic affections.

Glycerin (diluted) is one of the best agents to soften hardened and impacted cerumen prior to removing it by gently syringing with warm water. Any irritation caused by the hardened mass or the means of removal may be overcome by the following: Rx Colorless Hydrastis (Lloyd's), 1 fluidrachm; Glycerin, 20 drops; Distillate of Hamamelis, enough to make ½ fluidounce. Mix. Sig.: Apply warm to the parts by means of cotton. Glycerin is sometimes useful in otorrhea. A 5 per cent solution of phenol in glycerin upon cotton may be used for insertion into the aural canal after rupture of the membrana tympani when tenderness around the ear persists. It acts by dehydration, reducing the swelling and facilitating a more complete drainage from the middle ear.

Either glycerin or the glycerite of boro-glycerin are favorite agents for the depletion of the tissues in congestive and subacute inflammation of the womb.

It should be applied upon tampons so as to remain in contact for several hours, and then be followed by a hot (not warm) douche. The same treatment gives good results in uterine subinvolution. A small quantity of pure glycerin, or the glycerin suppository, is very effective in provoking a movement of the bowels when the feces are below the sigmoid flexure. For a small child it is one of the most effectual methods for overcoming constipation, with lack of rectal response to the calls of nature. Care should be had to see that the syringe tip is perfectly smooth, and any irritation caused by the glycerin may be due to using the enema too frequently or to the use of an impure glycerin. As a rule, ½ drachm properly and carefully injected is followed at once by a fecal evacuation. Diluted glycerin is sometimes useful to prevent bed-sores.

Glycerite of Starch is a useful application in ichthyosis, and glycerin pastes are more cleanly and effective than those made with petrolatum or fats. Montgomery advises a paste made as follows: Starch, Zinc Oxide, of each 1 part; Glycerin, 2 parts. Prepare without boiling. This forms a white paste of paint-like consistence, adherent, non-greasy and pliable, and may be applied by spreading with the hand. It holds the parts like a splint, allowing discharges free egress, while it does not interfere with the natural secretions. It is especially designed for papular skin eruptions.

A large proportion of the good derived from the magma-poultices, such as "Antiphlogistine", etc., are due to the antiseptic and dehydrating qualities of the glycerin they contain.

Internal. Only pure glycerin should be used for internal use. Glycerin is invaluable as a flavoring and sweetening preservative for water-dispensed medicines. Especially is it demanded in the summer season. From 1 to 2 drachms are sufficient for most four-ounce mixtures, depending somewhat upon the quantity of alcohol or other preservative agents present. In special cases of diabetes it may be used as a substitute for sugars. While somewhat laxative it is seldom so used in Eclectic practice, and if selected would be indicated only where either constipation or diarrhea is dependent upon fermentative changes. There are, however, cases of hemorrhoids, both bleeding and non-bleeding, in which it may be used as a laxative; and these are accompanied by fermentative action in the stomach and bowels. Glycerin is sometimes useful in fermentative dyspepsia, with flatulence and constipation, relieving largely by its antiseptic and dehydrating effects. Glycerin, well diluted with iced water, makes a fairly good drink for low forms of fever, where putrefaction is shown by the dry tongue, foul breath and sordes. Its value as a nutritional measure, in place of cod-liver oil and other fats, is open to grave doubt, with the probabilities in favor of its uselessness. Its employment as a food for diabetics, and in phthisis and other wasting diseases, has practically lost prestige, though in the first named many believe it useful to check, in some degree at least, the excretion of sugar. The common custom of taking glycerin, rock candy, and whisky for common coughs and colds is nothing less than a popular form of mild alcoholic tippling.

The Eclectic Materia Medica, Pharmacology and Therapeutics, 1922, was written by Harvey Wickes Felter, M.D.