ACTION OF TANNIC ACID ' 419 



Vnguentnm Oallw Cum Opio. (B. P.) 

 AcnwM Tannicum. Tannic Acid. HCwH„Oo. (U. S. & B. P.) 



Synonym. — Acidum gallo-tannicum, tanninum, tannin, digallic acid, E.; acid 

 tannique, tannin, Fr.; gerbsaure, tannin, G. 



A tannin usually obtained from nutgalls. 



Derivation. — Powdered nutgall is exposed to damp air for 48 liours. It is 

 tlien treated with water and ether. The water dissolves tannic acid; the ether 

 removes gallic acid, coloring matters and impurities. The mixture is filtered and 

 allowed to stand, when the lower aqueous layer yields tannic acid on evaporation. 



Properties. — A light yeUowish-white to light brown amorphous powder, gradu- 

 ally turning darker when exposed to air and light, usually cohering in the form 

 of glistening scales or spongy masses, odorless, or having a faint, characteristic 

 odor, and a strongly astringent taste. 



Very soluble in water and alcohol; also in about 1 part of glycerin, with the 

 application of a moderate heat; freely soluble in diluted alcohol, sparingly in 

 dehydrated alcohol; almost insoluble in absolute ether, chloroform, benzene, or 

 petroleum benzin. 



Incompatibles.- — Alkaloids, alkalies, mineral acids, silver, ferric, lead and anti- 

 mony salts, gelatin and emulsions. 



Dose.— H. & C, 3ss-Sss; (2-15) ; Sh. & Sw., 3ss-i, (2-4) ; D., gr.i-xv, (.06-1). 



PREPAKATIONS. 



Collodium Stypticum. Styptic Collodion. (U. S. P. 1905.) 

 Tannic acid, 20 ; alcohol, 5 ; ether, 25 ; collodion, to 100. Made by solution. 



Unguentum Acidi Tannici. Ointment of Tannic Acid. (U. S. P.) 

 Tannic acid, 20; glycerin, 20; ointment, 60. 



Olyceritmn Acidi Tannici. Glycerite of Tannic Acid. (U. S. & B. P.) 

 Tannic acid, 20; glycerin, 80. (U. S. P.) 



Administration. — Tannic acid is given in solution in aromatic waters, 

 alcohol, syrup, wine, glycerine, and water; also it is exhibited in powder. 

 The drug is used externally in powder, ointment, glycerite and lotion. 

 Suppositories containing tannic acid are sometimes introduced into the 

 rectum. 



Action External. — Tannic acid coagulates albumin, gelatin, and 

 fibrin. It has little effect upon the unbroken skin, but when applied to a 

 raw surface or mucous membrane, it coagulates and dries secretion, and so 

 fills up the mouths of glands, making the tissues harder, denser, and drier. 

 Tannic acid causes a species of "tanning" compatible with life, by 

 occasioning coagulation of the interstitial fluid in the tissues, abstraction 

 of moisture, and contraction of the cells of the part — through the forma- 

 tion of protein tannate. It is the most important astringent principle 

 contained in vegetable drugs. Tannic acid is, moreover, a local styptic or 

 hemostatic in arresting hemorrhage by contraction of the smooth muscles 

 of the vessel walls by coagulation of the blood, and constriction of the 

 tissues surrounding the blood vessels. Tannic acid causes arrest of leuko- 

 cyte movements, and diapedesis of the same, at the point of its applica- 

 tion. Tannic acid, although a slight local irritanb to raw surfaces, exerts 

 a depressing action upon the sensory nerve endings, and is essentially a 

 sedative in inflammatory conditions by causing ischemia. There are 

 several kinds of tannic acid, possessing slightly different chemical and 

 physiological properties. The official tannic acid — gallotannic acid — is 

 contained in nutgall and oak bark, while another variety — catechutannic 

 acid — is found in kino, catechu, etc. 



Action Internal. — Tannic acid dries the mouth by closure of glan- 



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