On the problem of optimum digitlaization in man.

: The low therapeutic index of cardiac glycoside requires an optimum individual digitalization. This is also a difficulty in the case of known serum glycoside concentrations because individual differences of biochemical and physiological factors (which influence both therapeutic and side effects) are important. As a rule the physician's criterion for an optimum digitalization is that side effects are avoided. This investigation attempted to find a measure for the effect of glycosides by noninvasive recording of parameters of myocardial contractility (systolic time intervals, STI). The measurements were made under oral digitalization with digoxin (Dilanacin). The serum glycoside concentration was determined by the radioimmunoassay method. The changes in STI were investigated in the rage of 1 to 3 ng digoxin per ml serum. In this concentration a significant correlation was demonstrated between STI shortening and glycoside level. It was found that the shortening of STI was maximum at the lowest concentration (1 ng/ml). It appears that the control of STI is for the physician a useful aid for an optimum digitalization in man.