The Excretion of Tritiated Digoxin

Six normal human volunteers as renal transplant donors were given 33H-digoxin before and again after unilateral nephrectomy. The serum digoxin concentration was modestly increased following nephrectomy, the serum digoxin half-time was slightly prolonged, and total digoxin excretion for the group was reduced by only 6.4% during a 7-day study. Four of the six patients studied before and after unilateral nephrectomy exhibited no important reduction in digoxin excretion after nephrectomy; two patients excreted only 66% and 64% as much of the administered dose of digoxin as they had excreted compared to the control study. The removal of one kidney from an individual whose remaining kidney is normal does not usually cause significant reduction in the excretion of tritiated digoxin, and one may conclude that in such instances nephrectomy should not in itself prompt a change in digoxin dosage provided the remaining kidney achieves its expected increased functional capacity. The adequacy of renal function determines digoxin excretion and the dosage of digoxin in these patients.