Comparative Studies on the Bioassay of Digitalis

Accurate determinations of the activity of digitalis preparations are probably more difficult to make than those of any other of the more important drugs used in medicine. This is due to the fact that digitalis is composed of various closely related active and inactive principles; the amount and proportions of which vary with the geographical source and climatic conditions under which the plant was grown; the activity of the drugs and its preparations is affected by the length and conditions of storage; chemical methods of assay are inadequate; and many factors in the various bioassay methods are difficult to control. It is therefore necessary to determine which bioassay results can most properly be applied to the determination of therapeutic dosage and clinical value. The investigations reported in this study were undertaken to compare the more important methods mentioned above.