Cardiac effects of once daily doses of 0.15 mg and 0.20 mg β-methyl digoxin

In this placebo-controlled study the cardiac effects of once daily doses of β-methyl digoxin 0.15 mg and 0.20 mg were evaluated using noninvasive methods. In double-blind fashion, 3 groups of 15 healthy volunteers each took 0.15 mg, or 0.20 mg β-methyl digoxin, or placebo for a period of 14 days. On the first 2 days, all volunteers received a double amount of tablets for digoxin loading. Before the start of the study and 12 h after the last dose, the following parameters were recorded: electrocardiogram (QTc, T wave amplitude), systemic time intervals (STI) (QS2c, PEP, PEPc, LVETc), and impedance cardiogram (Heather index). The mean digoxin serum concentrations were 0.648 ng/ml and 0.975 ng/ml respectively for the two doses. The typical glycoside effects were seen and there was shortening of the STI (QS2c: -12 ms/-14 ms resp.), flattening of the T wave, and a rise in the Heather index. The variations between baseline values and the 2 doses were statistically significant (p < 0.05). In most parameters, the more intensive effects corresponded with the higher serum level from the 0.20 mg dose; however, the difference between the 2 doses was not statistically significant. In conclusion, the results of this study show that a positive digitalis effect is demonstrable following the relatively small dose of β-methyl digoxin 0.15 mg once daily under long-term application in healthy volunteers.