Acute Vasodilator Therapy Increases Renal Clearance of Digoxin in Patients with Congestive Heart Failure

SUMMARY We studied the effect of vasodilator therapy on renal digoxin clearance in patients with chronic congestive heart failure. Intravenous administration of nitroprusside or hydralazine to eight patients with severe heart failure produced the expected increase in cardiac output and a decrease in central circulatory pressure. Renal clearance of sodium para-aminohippurate and estimated renal blood flow increased without a change in glomerular filtration rate. Total renal clearance of digoxin increased by 50 % during vasodilator therapy. Thus, acute administration of vasodilator increases renal digoxin clearance without changing glomerular filtration rate, suggesting an increase in tubular secretion of digoxin. Long-term vasodilator therapy may alter the maintenance dosage of digoxin required for optimal treatment of patients in congestive heart failure. IN PATIENTS with congestive heart failure, renal excretion of digoxin occurs as a result of glomerular filtration and net tubular secretion of unchanged drug.1 Tubular reabsorption of digoxin may also be important in patients with low urinary flow rates.2 Patients with congestive heart failure often have sub