Half-life of digoxin in myocardium after stopping maintenance treatment

The rate of decline of digoxin level in myocardium was estimated from operative samples of atrial and ventricular tissue from 40 patients undergoing cardiac surgery 1-20 days after maintenance digoxin treatment was stopped. Linear regression of myocardial log concentration-time curves for the group as a whole gave half-lives of 2.9 and 3.1 days in ventricular and atrial myocardium, respectively. Serum concentrations of digoxin were measured twice in each patient in this study: once while receiving treatment and once at the time of operation. Analysis of the 22 pairs of serum samples in which the second sample contained measurable levels of digoxin gave an estimated half-life of 2.3 days. The serum half-life was shorter than either the ventricular or the atrial myocardial half-life when data were analysed by unpaired statistics. Considering data only from those patients in whom the serum half-life was measured, to allow comparison by paired statistics, estimated ventricular and atrial half-lives were 1.5 and 1.3 days, respectively, which are significantly less than the respective serum half-lives of 2.3 and 2.1 days. Relatively slow clearance of digoxin from myocardium received further, anecdotal support from its demonstration in one patient 20 days after treatment was stopped.