The renal excretion of digoxin in the normal young subject.

Following the introduction of the embryonic duck heart assay method (1), and the radioactive isotope tracer technique (2), means were available for the quantitative study of the renal excretion of various cardioactive glycosides in both the experimental animal and man. It was but natural that the renal excretion of the digitalis glycoside, digitoxin, received the first attention of both the investigators employing the embryonic heart assay and those utilizing the radioactive method. Both groups agree exactly (3, 4) upon the amount of digitoxin excreted by man during the first 24 hours after administration. They also agree that the major portion of a given dose is destroyed and not excreted as intact digitoxin or a cardioactive metabolite of it. There is, however, some discrepancy in the quantitative estimates obtained by each group concerning the amount of cardioactive glycoside excreted after the first day of administration. This latter disagreement could be due to the fact that the group utilizing the embryonic duck heart method studied the renal excretion of glycoside in young, normal subjects, whereas the other group studied the same function in aged patients suffering from cardiac failure, subjects who have been found (3) to excrete far less unchanged digitoxin than the normal young subject. Thus, if some information has been obtained about the renal excretion of digitoxin, no quantitative studies have been done concerning the renal excretion of other useful, frequently employed cardioactive glycosides. One of these is digoxin, whose excretion has been assumed to be far more rapid than that of digitoxin. This belief is based upon the comparative rapidity with which both the therapeutic and toxic effects of digitalization disappear after cessation of administration of the drug (5). However, no quantitative renal measurements have been made. It was decided, therefore, to measure by means of the embryonic duck