A few more words on strophanthus / by George W. Balfour.

Date:
1896
Catalogue details

Licence: Public Domain Mark

Credit: A few more words on strophanthus / by George W. Balfour. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    difficult to see how there can be any comparison between the two. In Africa, its native habitat, strophanthus is employed as an arrow poison, and the natives have so great a dread of it that when told that the seeds were employed as a medicine in this country, “ they expressed the opinion that the English must be mad to employ so poisonous a substance for medicinal purposes.”1 The action of strophanthus on the heart is twofold : in small doses it arrests the heart in diastole, and in large doses it arrests it in systole.2 The diastolic type of action seems to be that which alone is useful therapeutically; in it the diastole is prolonged and the contractile energy of the myocardium at the same time increased. The type is thus that of bradycardia, a slow-beating heart sending forward a large blood-wave with each contraction,— not a type of heart usually associated with much vigour of the circulation. This type of heart action is produced only by small doses; and the excessive energy of the drug, the many preparations of strophanthus in the market, of varying composition and strength, must introduce an element of uncertainty in its employ- ment that cannot be devoid of anxiety. Strophanthus acts three thousand times more powerfully on the heart than digitalis;3 so that if some still dread digitalis as a dangerous cardiac poison, what must be their feelings towards strophanthus. And if it be difficult to select an appropriate dose of a drug of but moderate energy and only one action, how great must be the difficulty in the case of a drug of such excessive potency and possessing a twofold action on the heart. Indeed, whether we regard the un- certainty of its direction or its excessive energy as a poison, it seems difficult to formulate a more forcible indictment against any drug than that presented by a bare statement of the facts recorded against strophanthus by its most able investigator and most ardent advocate. But this is not all. Digitalis, as we have seen, acts equally upon all muscular fibre, and only more powerfully upon the heart and muscles of the arterioles because these organs receive from the blood within a given time a larger dose of the drug than the other muscles. The conditions as regards the circulation are perman- ently similar; and if strophanthus acted on all muscular fibre after the manner of digitalis, there would be a similar ratio between the action of the two drugs on the heart and on the arterioles, but this is not the case. Strophanthus acts three thousand times more powerfully on the heart than digitalis, but it acts one hundred times less powerfully than digitalis upon the muscles of the arterioles.4 There is thus no similarity whatever between the action of the two drugs. From the entire absence of any appreci- 1 Fraser on “Strophanthus Hispidus,” Transactions of the Royal Society of Edinburgh, vol. xxxv., part 4, p. 974. 2 Ibid., vol. xxxvi., part 2, p. 401. 3 Ibid., p. 403. i Ibid., pp. 438, 453.