[Prospective examinations of digitalis poisoning]

Despite many years of using digitalis to treat congestive heart failure, the problem of intoxication has remained unchanged. In nine prospective studies on patients under a maintenance treatment with digoxin the intoxication rate ranged from 15.2% to 27.5%. Other studies have also shown that renal insufficiency was present in 70% of intoxicated patients. In contrast the digitoxin toxicity rate, as shown in two prospective studies from Norway and France on 649 and 2120 patients respectively, resulted in an intoxication rate of 5.8% and 3.2% respectively. The explanation for the discrepancy between the two glycosides seems to be predominantly the influence of renal function on drug elimination. Digoxin is mainly excreted through the kidneys; an impairment of the renal function will therefore lead to a reduced elimination of this drug. In these cases a dose reduction of digoxin is necessary. Digitoxin on the other hand is excreted both through the kidneys and the bile. Impairment of the renal function does, therefore, not lead to any decrease in digitoxin elimination whether in renal disease, during heart failure or in old age. In contrast to digoxin, no dose reduction is necessary with digitoxin when renal function is reduced. Digitoxin is therefore easier to handle in the long term management of cardiac patients with and without renal impairment.