Thymol (U. S. P.)—Thymol.

Related entry: Thymus.—Thyme

"A phenol occuring in the volatile oils of Thymus vulgaris, Linné, Monarda punctata, Linné (Nat. Ord.—Labiatae), and Carum Ajowan (Roxburgh), Bentham et Hooker (Nat. Ord.—Umbelliferae). It should be kept in well-stoppered bottles"—(U. S. P.).
SYNONYMS: Acidum thymicum, Thymic acid.

Source, History, and Preparation.—Thymol was discovered by Caspar Neumann in 1719. It was purified, in 1853, by M. Lallemand, who gave it the name "thymol," and ascribed the formula (old notation) C20H14O2, the same being accepted at the present day as correct, corresponding to C10H14O of the new notation. Thymol is a phenol (iso-propyl-meta-cresol), and is isomeric with carvacrol (iso-propyl-ortho-cresol). It is found in oil of thyme, oil of horsemint, and oil of Carum Ajowan, De Candolle (Ptychotis Ajowan), a plant from the East Indies; the thymol of commerce being derived from thyme oil. The yield of thymol from this source, however, is comparatively small and quite variable (from less than 1 to 38 per cent; see Amer. Jour. Pharm., 1882, p. 521). Larger quantities of thymol occur in the oil of horsemint (see Monarda). Thymol exists in oil of thyme, associated with two hydrocarbons of greater volatility, cymol (C10H14), and thymene (C10C16) (see Oleum Thymi). Thymol may be obtained by fractionally distilling the pure oil of thyme; cymene and thymene pass over, and afterward the thymol, which may be purified by crystallization from alcohol; or, the thyme oil may be agitated with solution of caustic soda, the hydrocarbons forming the tipper layer are removed, and the lower solution containing the thymolate of sodium is neutralized with hydrochloric acid, when thymol will rise to the surface, and may be purified by crystallization from its alcoholic solution.

Description.—Thymol, as described by the U. S. P., forms "large, colorless, translucent crystals of the hexagonal system, having an aromatic, thyme-like odor, and a pungent, aromatic taste, with a very slight caustic effect upon the lips. Its specific gravity, as a solid, is 1.069 at 15° C. (59° F.), but when liquefied by fusion it is lighter than water. It melts at 50° to 51° C. (122° to 123.8° F.), remaining liquid at considerably lower temperatures. When triturated with about equal quantities of camphor, menthol, or chloral, it liquefies. Soluble in about 1200 parts of water at 15° C. (59° F.), and in less than its own weight of alcohol, ether, or chloroform; also readily soluble in carbon disulphide, glacial acetic acid, and in fixed or volatile oils. Its alcoholic solution is optically inactive"—(U. S. P.). Being a phenol, thymol readily dissolves in caustic alkalies and is regenerated by acids, even carbonic acid (see Preparation, above). Thymol also dissolves in 120 parts of glycerin. In making solutions of thymol with glycerin and water, it is best to triturate the thymol in a mortar with a small portion of alcohol, until it is dissolved, then add the desired menstruum. Thymol boils at 230° C. (446° F.) (Doveri and Lallemand).

Tests.—"If a very small crystal of thymol be dissolved in 1 Cc. of glacial acetic acid, and then 6 drops of sulphuric acid and 1 drop of nitric acid be added, the liquid will assume a deep bluish-green color. If 1 Gm. of thymol be heated in a test-tube, in a water-bath, with 5 Cc. of a 10 per cent solution of sodium hydrate, a clear, colorless, or very slightly reddish solution should be formed, which becomes darker on standing, but without the separation of oily drops (absence of thymen, or laevogyrate pinene (C10H16). If to this a few drops of chloroform be added, and the mixture agitated, a violet color will be produced. When a crystal of thymol is heated in an open capsule, or in a watch-glass, on a waterbath, it should gradually volatilize, leaving no residue (absence of paraffin, spermaceti, etc.)"—(U. S. P.).

Action, Medical Uses, and Dosage.—Thymol is an antiseptic and disinfectant, and is considered by many who have experimented with it, to be superior, in these respects, to carbolic acid. By destroying the vitality of organized and living ferments, it prevents the occurrence of putrefaction, and arrests it when it has commenced. Ɣ A small quantity of thymol added to albumen, milk, solutions of gum, or of gelatin, will preserve them for several months; and urine will be kept intact for several weeks. In contact with putrid pus, it promptly removes any odor emanating from this substance, and keeps it without change until complete desiccation occurs. Applied to wounds, ulcers, or abscesses, in the form of a weak solution, it promptly modifies their condition, and accelerates cicatrization. Fifteen grains of thymol dissolved in 2 pints of distilled water, forms an invaluable disinfectant; this has been found effective in disinfecting sick rooms, and as a local application to prevent septicemia during the parturient period, as well as at other times when there is reason to fear its development. M. Paquet has preserved viscera, portions of limbs, etc., free from the least trace of putrefaction for several months, by means of the following solution: Take of thymol, tannin, each, 1 drachm; anilin, ½ drachm; glycerin, 3 ounces. Mix. When employed in the dressing of ulcers, etc., the following solution has been recommended by M. Giraldes: Take of thymol, from ½ to 1 drachm; alcohol, 3 fluid ounces; distilled water, 30 fluid ounces. Mix. This has been found to act efficiently, even in cases in which iodine and other analogous topical applications had been fruitlessly employed. It is not necessary to employ too strong a solution, as pure thymol possesses caustic properties. M. Paquet has derived great benefit in dressing ulcers by the following: Take of thymol, ½ drachm; alcohol (85 per cent), 2 fluid drachms; distilled water, 33 fluid ounces. Mix. These solutions may be applied on lint, or by spray. Concentrated thymol may be advantageously substituted for nitric acid, or nitrate of silver, in cauterization of the dental nerves; its odor is not so disagreeable as that of carbolic acid.

Thymol has been employed in inhalations, by Bouillhon, Paquet, and others, in bronchial and other affections of the respiratory organs, attended with gangrenous exhalations. The respiratory mucous membranes become excited, the expectoration is diminished, becomes thinner and less tenacious, contains a much smaller amount of mucin, and is more freely passed. It suppresses the gangrenous odor, and prevents the diseased bronchial surfaces and the abnormal secretions covering them, from undergoing butyric fermentation, thus checking a poisoning of the blood. Ten drops of a thick, concentrated solution of thymol are placed in a small glass flask, furnished with a cork, through which pass two bent glass tubes, one descending nearly to the bottom of the flask, the other being short. This latter is held in the patient's mouth, who will aspire the air charged with the vapor of the thymol. These inhalations should be continued for 4 or 5 minutes, each time, and be repeated 8 or 10 times per day. Ten drops of the solution will suffice for inhalation during 4 or 5 days. If, during the inhalation, a slight sense of pricking is experienced in the posterior region of the pharynx, the inhalation should be suspended until this sensation passes off, and then be again continued. M. Lewin considers thymol very useful in diphtheria and other similar diseases dependent upon the action of living organisms; also in arresting the hypersecretion of various mucous membranes. In cases in which fermentation occurs in the stomach with dilatation of this organ, he states that thymol acts promptly in arresting the accompanying vomitings, and gradually effects a contraction of this dilated cavity.

M. Baelz, who has made some comparative experiments with thymol and salicylic acid (in the service of M. Wunderlich) upon persons in health, and also those affected with typhoid fever, articular rheumatism, phthisis, and pyelitis, states that in doses of ⅙ of a grain, repeated several times, no effect was observed; in order to obtain an appreciable therapeutical result, it was necessary to give daily from 25 to 30 grains. Upon coming in contact with the bucco-pharyngeal mucous membrane, the medicine occasioned a pricking sensation and a disagreeable taste; there was seldom any nausea, and vomiting occurred but once among 36 persons. Upon increasing the dose, a slight, but transient, sense of heat was experienced in the epigastrium; and, in some cases, a diarrhoea analogous to that in typhoid fever. In the majority of cases, half an hour or an hour after the ingestion of thymol, more or less limited and profuse sweats appeared, but in all cases less than those occasioned by salicylic acid or jaborandi. An increase in the quantity of urine was frequently noticed; and the urine presented a dark, greenish color, as if it contained blood, and appeared a yellowish-brown when illuminated by reflected light. A solution of perchloride of iron added to the urine rendered it cloudy, and of a whitish-gray color. When the gray predominated, it reminded one of an icteric urine, or even of a nephritic urine mixed with blood; the absence of albumen, however, prevented any mistake as to the latter cause. The nervous phenomena were represented by tinnitus aurium, deafness, and a sense of constriction at the temples (Archiv der Heilkunde, Vol. XIV, Parts III and IV). In doses of from 30 to 60 grains, M. Baelz considers its action, as an antipyretic, decidedly inferior to that of salicylic acid.

Dr. B. Kussner has found that from 3 to 5 drops of a 1 per cent solution of thymol is beneficial in diarrhoea of children. Thymol injected into the veins lowers the temperature and induces stupor. Animals poisoned with it pass into a deep coma; after death their blood is dark and fluid, but no fatty degeneration of internal organs is observed (Med. Press and Circ.). Prof. Webster reports a satisfactory use of thymol in expelling tapeworm. A cathartic is administered at night, and 10 grains of thymol administered in the morning every 15 minutes until the worm is expelled. As it is a powerful depressant, it must be carefully used. It is a remedy for chyluria.

The preferable forms, for the internal administration of thymol are either to dissolve it in an alcoholic drink, or to form it into a thick, emulsioned fluid; but, thus far, the employment of this agent has been confined chiefly to its use as a topical application, and to utilize its antiseptic properties. The advantages derived from its internal administration have been very limited. The following has been advised as a method of preparing it into pills, the soap being indispensable to assure the division of the thymol: Take of thymol, 3 grains; medicinal soap, 6 grains; excipient, a sufficient quantity. Mix thoroughly, and divide into 20 pills. An ointment has likewise been advantageously employed, by thoroughly triturating together from 2 to 20 drops of a thick, alcoholic solution of thymol with 1 ounce of petrolatum or pure lard. This has been used as a local application in burns, eczema, psoriasis, tinea, lichen, and other cutaneous affections and as a parasiticide. When much hyperemia is present, it must not be applied until this has been allayed. A very powerful antiseptic may be made thus: 1 part of thymol and 12 parts of chloral hydrate are triturated together, and then an equal quantity of camphor added, when the mixture assumes a liquid form; these proportions may be varied, if deemed necessary. Thymol enters into various antiseptic compounds used as local applications, for catarrhal conditions, etc.

Derivative.—THYMACETIN (CH3.CO.NH.C6H2[OC2H5].[CH3].[C3H7]). This substance is analogous to phenacetin, inasmuch as the phenol of the latter is substituted by thymol. It is a crystalline white powder, but little soluble in water. In doses of about 7 grains it is credited with hypnotic power. Analgesic properties are also possessed by it. Functional nervous and neuralgic headaches, and mental and other nervous disorders have been successfully treated with it. The dose ranges from 3 to 15 grains. It combines the properties of phenacetin with the antiseptic power of thymol.

Related Preparation.—LISTERINE. Listerine is an agreeable non-irritant and non-escharotic antiseptic preparation composed of the essential antiseptic constituents of thyme, eucalyptus, gaultheria, baptisia, and Mentha arvensis combined with refined benzo-boracic acid. Listerine is a transparent amber-colored fluid becoming cloudy or opaque below 60° F., but clearing again as the temperature reaches that figure. It has a fragrant, aromatic odor, a ungent taste, and in reaction is slightly acid. It mixes clear with water in all proportions. It is very extensively employed in the antiseptic treatment of operative and accidental wounds, and as a general cleansing agent in medical and dental practice. Its range of usefulness is practically unlimited in surgery, gynaecology, urino-genital disorders, and dental practice, being used as a deodorant and antiseptic wash. Internally it is administered in many fermentative gastro-intestinal affections requiring the stimulant and antiseptic properties of such a combination. It may be used freely, full strength or diluted, as a gargle, mouth-wash, spray, injection or inhalation. The dose for internal use is 1 fluid drachm, in, 3 or 4 times a day, full strength or diluted with water. Listerine is a specialty of the Lambert Pharmacal Company of St. Louis.

King's American Dispensatory, 1898, was written by Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D.