Related entry: Digitalis Leaves
Synonym.—Digitaline cristallisée (Ph.Fr.).
C34H54O11 = 638.432.
Digitoxin, C34H54O11, is a glucoside obtained from digitalis leaves. It occurs in colourless crystals, or as a white crystalline powder, odourless, and bitter, and may contain five molecules of water of crystallisation. Anhydrous digitoxin contracts in bulk at 240°; the hydrated form melts at 145°. It gives a precipitate with tannic acid. If a little digitoxin be dissolved in 3 or 4 mils of glacial acetic acid, a drop of dilute solution of ferric chloride added, and then concentrated sulphuric acid poured down so as to form a layer under the acetic acid solution, a dull brownish-green band first appears; this quickly alters, so that the uppermost layer of the sulphuric acid is coloured brownish-red, while above this a broad, intense, bluish-green band appears, which soon changes to indigo-blue; after thirty-six to forty-eight hours a green colour again appears, which then, after a longer time, fades to a dirty brown (Keller's reaction). Heated on a water-bath for some time with concentrated hydrochloric acid, a green or brownish-green colour is obtained, which gives a cloudy greenish-yellow solution on diluting with water. "Digitaline cristallisée, Nativelle," and "Digitaline amorphe, Homolle," consist largely of digitoxin, but a German variety of so-called "crystalline digitalin," consists of digitonin. A solution of digitoxin is prepared under the trade-name Digalen. One mil contains 0.3 milligram of glucoside, and is stated to be equivalent to 0.15 gramme of digitalis leaf. Digalen is given by the mouth or by intravenous or subcutaneous injection in doses of from ½ to 1 mil (8 to 15 minims).
Insoluble in water; soluble in alcohol, chloroform, or ether.
Action and Uses.—Digitoxin is the most powerful of the glucosides which have been extracted from digitalis leaves, but owing to slow excretion it is cumulative in its action. It may be prepared in solution (1 in 1000), by using as a solvent 90 per cent. alcohol, 6 parts, adding glycerin, 3 parts, and water, 1 part. Pills may be prepared by careful trituration of the digitoxin with sugar of milk and massing with glycerin of tragacanth. Digitoxin is not considered suitable for hypodermic injection; it may be given rectally in doses of ½ to ¾ milligram (1/120 to 1/80 grain). In cases of poisoning use the stomach pump, apply mustard plasters, and give emetics, tannin, nitroglycerin, morphine, alcoholic stimulants, or camphor.
Dose.—¼ milligram (1/250 grain), increased to 1 milligram (1/64 grain).