A Difference in Cardiodecelerator Action Between Digitoxin and Digitoxigenin.

There is a qualitative difference between the circulatory action of digitoxin and that of its aglucone, digitoxigenin. Digitoxigenin causes an immediate and transient cardiodeceleration due to a central stimulation of the vagus. Digitoxin is without effect if administered in equimolar doses under the same experimental conditions. This pharmacological difference between digitoxin and its genin was demonstrated and analyzed with the use of the innervated heart-lung preparation of the dog in which the drugs could be administered into the blood supply to the central nervous system without reaching the heart-lung circuit.