Influence of canrenoate-K and cardiac glycosides on their tissue distribution and elimination

The combination of cardiac glycosides and canrenoate-potassium (CR-K) produces synergistic effects on hemodynamics. On the other hand, CR-K antagonizes digitalis-induced cardiac arrhythmias. Therefore, it was the purpose of this study to determine interactions between these substances, particularly of their myocardial uptake. The additional administration of CR-K leads to significantly higher concentrations of digoxin and ouabain in heart, liver, adrenal gland and spleen. Contrary to this, additional digoxin reduces the concentration of CR-K in the tissue. Particularly obvious is the reduced concentration in the kidney, adrenal gland, pancreas, brain and spleen. The renal excretion of digoxin and ouabain is reduced by the additional administration of CR-K, while digoxin accelerates the CR-K excretion within the first 60 min after application. Metabolic interference was not detected in the combination of cardiac glycosides and CR-K. The mechanisms for the interactions between cardiac glycosides and CR-K during the distribution phase are discussed. The inhomogenous interference of their myocardial uptake makes a common cardiac receptor for the synergistic effect of cardiac glycosides and CR-K rather unlikely. CR-K does not have a suppressant effect on digitalis-induced arrhythmias due to any diminution of the glycoside uptake by myocardial tissue.