Definition. - A monobasic organic acid, C13H9O7.COOH, obtained from nutgall.

Description and Properties. - A light-yellowish, amorphous powder, usually cohering in the form of glistening scales or spongy masses; odorless or with a faint characteristic odor and a strongly astringent taste; gradually turning darker when exposed to air and light. Soluble in about 0.34 part of water and in 0.23 part of alcohol; very soluble in boiling water and in boiling alcohol; also soluble in about 1 part of glycerin with the assistance of a moderate heat; freely soluble in diluted alcohol and sparingly in absolute alcohol; almost insoluble in absolute ether, chloroform, benzol, or benzin.

Dose. - 1-20 grains (0.06-1.2 Gm.) [7 1/2 grains (0.5 Gm.), U. S. P.].

Official Preparations

Collodium Stypticum - Collodii Styptici - Styptic Collodion. - Used externally and locally. (Tannic acid, 20; alcohol, 5; ether, 25; collodion, to 100.)

Glyceritum Acidi Tannici - Glyceriti Acidi Tannici - Glycerite of Tannic Acid. - Used externally and locally. (Tannic acid, 20; glycerin, 60.)

Trochisci Acidi Tannici - Trochiscos (acc.) Acidi Tannici - Troches of Tannic Acid. - Dose, 1-3 troches.

Unguentum Acidi Tannici - Ungenti Acidi Tannici - Ointment of Tannic Acid. - Used externally and locally. (Tannic acid, 20; glycerin, 20; ointment, 60.)

Antagonists and Incompatibles. - The vegetable astringents are incompatible with the salts of iron (ferric and ferrous), and also with the salts of lead, silver, antimony, and copper; with the alkaloids, the glucosides, and gelatin; and with the alkalies and mineral acids and emulsions. Spirit of nitrous ether is incompatible with gallic acid.

Synergists. - Tonics and bitters, and also agents increasing waste, favor the action of vegetable astringents.

Physiological Action. - Externally. - Tannic acid has little, if any, effect upon the unbroken skin. It is feebly antiseptic. Upon raw surfaces, however, it acts as a powerful astringent, contracting the tissues and coagulating the albumin. Urticaria and erythema sometimes follow its use. In weak solutions it tans dead skin. Locally applied to glandular structures, such as sweat glands, tannic acid causes a diminution in their secretions.

Internally. - Digestive System. - By coagulating the albumins tannic acid imparts a dryness to the mouth, accompanied by a sensation of puckering. It partially paralyzes the sensory nerve-572 endings, thus blunting the sense of taste. Large doses produce vomiting by an irritant action, while diarrhea, followed by constipation, may be present.

By its action on- the stomach, pepsin and peptones are precipitated, unless the stomach contents are markedly acid, albumin is coagulated, and the secretion of gastric juice diminished, all of which actions tend to impair the digestive function. The tannates formed are all susceptible of digestion, however, and tannic acid is set free. There is a partial conversion of the tannic acid into gallic and pyro-gallic acids. To facilitate absorption there must be a preliminary conversion of tannic into gallic acid, and this reaction takes place in the intestine. A diminution of peristalsis is followed by constipation.

Circulatory System. - Its astringent property makes tannic acid a valuable hemostatic. It arrests hemorrhage partly by preliminary contraction of the blood-vessels, but more particularly by coagulating the proteid of the blood.

Nervous System. - No special effect has been observed.

Absorption and Elimination. - As tannic acid combines so readily with the proteids of the intestinal canal it is not absorbed, as a rule, in large amounts. Some of the ingested tannic acid is eliminated unchanged by the intestines. Most of it is converted into gallic acid in the intestines, and as such is eliminated by the urine and stools. The tannate that is absorbed may be found in the blood, possibly a sodium salt of tannic or gallic acids. Sodium tannate may be found in the urine. Much of the tannic acid taken up is completely oxidized.

Uterus. - No special influence other than arresting hemorrhage when locally applied has been noted.

Untoward Action. - A dose of 3 grains (0.2 Gm.) may cause pain in the stomach and intestines. Following such a dose, there may be coating of the tongue, thirst, eructation of gas, and tenesmus. A tendency to hemorrhoidal congestion is enhanced.

Therapeutics. - Externally and Locally. - Tannic acid is a valuable application for bedsores and ulcers. Its astringent property is of use in cases of intertrigo, impetigo, sycosis, sore nipples, and eczema of the chronic desquamating variety. It is beneficial in hyperidrosis of the hands and feet, of the axillae and genitals.

The glycerite of tannin, applied locally in cases of otorrhea and ozena as sequelae of scarlet fever or measles, is of some benefit. The same preparation or a powder may be used in stomatitis, tonsillitis, and pharyngitis, as well as in cases of spongy or ulcerous gums. The lozenges are beneficial in whooping-cough. Suppositories of tannic acid are employed for hemorrhoids, fissure, prolapse, and rectal ulcers.

An aqueous solution of tannic acid is very useful in leukor-rhea. The glycerite and iodoform tannin are excellent agents in inflammation of the cervix uteri. Tannic acid also dispels the odor and allays the discharges in carcinoma uteri, being applied as a vaginal douche. It is useful as a lotion in herpes and alopecia circumscripta. Injection of the acid or insufflation of the powder into the urethra is of some value in gonorrhea. In acute dysentery much benefit may be derived from an enema of 10 grains of tannin added to a 4 per cent. solution of boric acid. It lessens pain and tenesmus and controls hemorrhage.

Internally. - Tannic acid is styptic in intestinal hemorrhage and is valuable in treatment of diarrhea. It forms tannates when given as an antidote for poisoning by alkaloids and tartar emetic. Since these tannates are more or less soluble, however, some drug should be given as a purgative.

Administration. - For hematemesis powders of 10-20 grains are given. For effect upon the intestines it should be administered in pills, 3-5 grains, or it may be dissolved in the stomach. Locally it may be applied as a solution, glycerite, powder, suppository, or an ointment. Styptic collodion is a protection to lacerated or incised wounds.

Organic Combinations of Tannin.

Because of its irritating properties in the gastro-intestinal canal, tannic acid has been largely supplanted by a number of organic combinations. Among these are tannalbin, tannigen, tannoform, tannon (tannopin), and tannocol.

Tannalbin. - This is a compound of tannin and albumin, heated to 120o F. It is obtained as a red-brown powder, and is decomposed by the alkaline secretions of the intestinal canal and not by the gastric juice. It is one of the best of these newer compounds in the treatment of intestinal diarrhea if such diarrheas call for astringent action. The dose of tannalbin is from 45-150 grains (3-10 Gm.) for adults, children in proportion.

Tannigen. - This is a yellowish-gray powder - an acetic ester of tannic acid. It is odorless and tasteless, hygroscopic, insoluble in water, and slightly soluble in ether and alcohol. It acts best in the alkaline secretions, and is not acted on, or but slightly (Rost), by the gastric secretions. It is useful as an intestinal astringent in chronic diarrheas in about the same dosage as tannalbin.

Tannoform. - This is a product of condensation formed by the action of formal-dehyd on gallotannic acids. It is a pale rose-colored powder, insoluble in water and soluble in alkaline solutions. It is valuable in diarrheas associated with much fermentation, and is also used as a topical application (as 10 per cent. ointment) in ozena, burns, hyperidrosis, pruritus, and hemorrhoids. Its dose internally is from 5-8 grains (0.25-0.5 Gm.). A number of tannoforms may be formed from the vegetable astringents, such as rubus, juglans, rhatany, catechu, quercus, etc.

Tannon, also called tannopin, is a combination of urotropin and tannin. It is a light-brown powder, insoluble in water and soluble in weak alkaline fluids. It has been recommended in diarrhea in 15-grain doses (1 Gm.).

Tannocol. - This combination of tannic acid and gelatin is practically identical with tannalbin.