DIGITONIN. — Soluble in water and alcohol, appears in the form of yellow grannies, but possesses none of the prop erties for which digitalis is celebrated. It appears to be identical, or at least closely related, to saponin, the active principle of quilliai bark.
lhontx.—Digitin is a coarsely-granu lated, crystalline powder, soluble in hol, ether, and alkaline solutions, and is physiologically and therapeutically inert. DIGITALIRESIN. — DigitalireSin and digitoxiresin purport to be derivatives, respectively, of the digitalin and digi toxin of Schiniedeberg, but beyond this nothing- is known of either.
A comparative study of digitalis and its derivatives shows that: 1. Digitalis and digitoxin each represent the full circulatory powers of digitalis. 2. Digi talis, digitalin, and digitoxin stimulate the cardio-inhibitory mechanism both centrally and peripherally. In larger doses they paralyze the intrinsic eardio inhibitory apparatus. 3. They all cause a rise of blood-pressure by stimulating the heart and constricting the blood vessels. 4. Very large doses paralyze the heart-muscle of the mammal, the organ stopping in diastole. 5. Digitalin of Merck is a stable compound, 1 gramme of it being equivalent to about 70 cubic centimetres of tincture of digitalis. G. Digitoxin is not to be recommended for human medication on account of its irri tant action, which makes it liable to upset the stomach when given by the mouth, or to cause abscess when given hypodermically, and on account of its insolubility, which renders it slowly ab sorbed and irregularly eliminated, having a marked tendency to cumulative action. Arnold and Wood (Amer. Jour. of Med. Sciences, Aug., 1900).
Digitalis as obtained from various re gions shows entirely regular alterations at different periods of the year. These alterations are always in direct associa tion with certain definite periods of the year, the general result being that the old leaves found tOward the beginning of August have customarily only about one-fourth the activity of the new leaves. D. Focke (Zcits. f. Med., vol. xlvi, Nos. 5 and G, 1902).
When digitoxin is employed, it is rec ommended that a solution be made in alcohol, chloroform, and water, and that it be administered by clyster: digitoxin, 1/06 to 1/64 grain; chloroform, 4 minims; 90-degree alcohol, 1 drachm; water, to make 14 drachms; at one dose.
Physiological Action.—Though digi talis per se has been before the medical profession for more than three centuries, the fact remains that its physiological attributes are by no means thoroughly understood; indeed, they constitute a subject on which there is great differ ence of opinion. It may be affirmed that experiments upon mammals, birds, and batrachians have added practically nothing to the knowledge already pos sessed regarding the action of digitalis when introduced into the economy of man. Part of the trouble may have
arisen from the fact that many of the preparations as found in shops are prac tically inert, while the different dosage and forms of exhibition as employed by different observers inhibit uniformity. The action on the two-chambered heart of the frog, or three-chambered heart of the bird, both of which animals excrete solid urea, cannot coincide with that on the four-chambered heart and the fluid excreting renal gland of the mammal, while, as is well known, there are few drugs toward which individual mem bers of the human family are so generally and differently idiosyncratic. .Again, the actions of watery and alcoholic prep arations are by no means identical, owing to the differences in the solubility of the various glucosides in these menstrua; an infusion, for instance, holds in solution chiefly the digitonin, while the tincture contains digitalin and digitalein, — neither contains much digitoxin, but the tincture necessarily carries more than the infusion. Notably the infusion is more directly and promptly diuretic, and the B. P. tincture more so than that of the U. S. P., but the latter two afford the best results when the heal t alone is to be acted on. But it is doubtful if the tincture alone ever acts as a true diuretic, except in the presence of a heart-lesion, such as is found in connec tion with some form of hydrops. The drug often fails completely in securing the desired action clinically, because the wrong preparation is employed, and it may here be noted that little reliance is to be put on the glucosides, at least not until we are possessed of more definite knowledge regarding their composition and physiological relations. Not only is their use to be deprecated, but they are generally dangerous and sometimes re medially worthless. Digitoxin especially is so highly toxic and so difficult of elimination as properly to bar it from official recognition. How often is seen the statement that digitalis is a power ful sedative, and again that it is a heart stimulant? This conveys little informa tion, because it is conflicting; yet it may be true, and depends solely upon the dosage, and the peculiarities of the in dividual patient. In fact, there is no drug in the materia medica that requires more careful handling or more careful study of effects in each and every one for whom it is prescribed; and again there is no drug more certain in secur ing definite results, when intelligently exhibited.