This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol2", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
Digitalis has already been treated of generally with the nervous sedatives (II. 103). it is here to be considered only as a diuretic. in this capacity, it is certainly one of the most efficient medicines known.
in the cautious mode in which it is usually deemed safest to administer digitalis, in order to avoid its dangerous depressing effects, and guard against its cumulative tendency, it is slow in its diuretic operation. Several days almost always elapse before any effect is experienced; generally it is not until after a week or two, that its full influence is felt; and sometimes, even when, in the end, it may act energetically, the result is postponed much longer. No doubt, its influence on the kidneys might be sooner obtained by a more energetic administration; but the advantage gained would not be equivalent to the danger incurred. When it does begin to operate, the effect is often sudden and striking. I have visited patients upon one day, passing not more than a pint of urine in twenty-four hours, and, upon the next visit, have found them passing a gallon or more in the same time. The effect, too, after it has begun, continues in general without abatement for several days, even though the medicine should be withheld; and it is a good rule to diminish the dose somewhat, upon the occurrence of profuse diuresis, for fear of too great an accumulation. Should the effect diminish, the original dose must be resumed.
The opinion has been advanced, that digitalis operates as a diuretic, not by a direct action on the kidneys, but by promoting absorption; and the opinion is supported upon the ground, that it does not produce an increased secretion of urine, unless there may be dropsical effusion. But the fact is, that digitalis will sometimes prove diuretic in health; and, if less copiously so than in dropsy, it is probably because there is less liquid in the blood to be eliminated than when the deficiency, produced by the secretory act, can be instantly supplied by the liquid from the tissues and cavities.
Another opinion is, that both the absorption and diuresis are connected with the depressed state of the circulation; the feebleness of the movement of the blood being supposed to favour the endosmose of liquid from the cavities into the circulation, and its presence there to be the exciting cause of the increased action of the kidneys. But here, again, hypothesis is opposed by fact; for digitalis will often operate as a diuretic, without any appreciable effect on the pulse. Besides, against all the views which refuse to the medicine a direct action on the kidneys is the insurmountable objection that, supposing the dropsical effusion to be absorbed, if the kidneys remain in the same torpid condition, either the liquid taken up will escape again as it did originally, or find its way out of the system, by some other emunctory, as that of the skin, lungs, or bowels.
It is impossible to account for all the effects of digitalis, without admitting a direct action on the kidneys. This may very possibly be aided by its absorbent influence consequent on the depression of the circulation, but certainly does not exclusively depend upon it. From the experiments of Dr. W. A. Hammond, of the U. S. Army, it would appear, while increasing the amount of water discharged by urine, not materially to alter the quantity of solid matters. (Am. Journ. of lied. Sci., Jan. 1859, p. 215.)
As a diuretic, digitalis is given only in dropsy; and there is no variety of this disease, strictly speaking, in which it may not be used with a prospect of advantage; for ovarian dropsy and infantile meningitis, in which it is admitted that the medicine is of little or no service, though they are frequently designated as dropsies, are not entitled to the name; at least they are pathologically distinct from the other forms of the disease. Even in dropsies attended with the lowest grade of general strength, there is no positive contraindication to the medicine; for its depressing effects, when it is cautiously managed, may be readily counteracted by the conjoint use of supporting measures.
But certainly we cannot say of the remedy, what Dr. Withering is stated by Dr. Chapman, in his Therapeutics (2d ed., i. 284), to have declared of it, that "so far as the removal of the water will contribute to cure the patients, so much may be expected from this medicine." On the contrary, the medicine not unfrequently fails entirely to act on the kidneys; and I have seen patients prostrated, under its depressing influence, to the lowest point compatible with safety, in whom, nevertheless, no diuretic effect was produced.
Attempts have been made to indicate the circumstances under which digitalis will be most likely to act efficiently. My own experience coincides with that of Dr. Blackall, who found it most successful in cases attended with coagulable urine; at least I can say truly that no remedy in my hands has seemed equally efficacious, in the dropsies with this condition of the urine, unless possibly bitartrate of potassa. I have witnessed several cases of what appeared to be decided and obstinate attacks of Bright's disease, with universal dropsy, and unconnected with scarlatina, which yielded completely and permanently to the use of digitalis; and I am convinced that, in some of the cases, it exercises a positively curative influence on the kidneys, independently of the mere increase of their secretion.
Another condition of dropsy to which it is especially applicable, is that which complicates cardiac affections, of a character calling at the same time for the sedative action of the remedy on the heart.
The commencing dose of the powdered leaves as a diuretic is a grain, which may be repeated three times a day, and increased every other day by one-quarter, or one-half, until its effects begin to be felt, either upon the kidneys, heart, or nervous system. For the dose and method of using the other officinal preparations, I would refer the reader to the article on digitalis among the nervous sedatives (II. 121). in relation to the infusion, which has been thought by some to be the most effectual diuretic preparation of the medicine, I would simply say, that any superiority of effect obtained from it may be ascribed to the much larger proportional dose in which it is usually given, than either the powder or the tincture. All the preparations are efficient, if well made, and from good material.* I usually prefer the powder, prepared immediately from the green portion of the leaves, without the midrib or footstalk.
Great advantage often accrues from giving other medicines with digitalis, either to meet some coincident indication, or to aid in producing its diuretic effect. Thus, in anemic states of the system, it may be combined with iron, in the plethoric or febrile, with bitartrate or nitrate of potassa, and in pectoral and hepatic dropsies, often with calomel.
It has been used externally, with asserted success, in promoting diuresis, especially in cases of abdominal dropsy. This method may be resorted to when digitalis is not well borne on the stomach, or when it fails to act in the ordinary method. For this purpose, the tincture may be applied by friction to the inside of the thighs and arms, or a strong decoction may be placed, in the form of a cataplasm, or by means of linen cloths saturated with it, over the abdomen. The endermic method is inapplicable, as digitalis is too irritant in its local operation.