Acute effects of intravenous furosemide administration on serum digoxin concentration

The effect of intravenous (IV) furosemide (2.5 mg/kg) on serum digoxin concentration, urine flow rate, and myocardial contractility and rhythm was studied in normal dogs and dogs treated with digoxin. Furosemide IV to animals which had not been receiving digoxin resulted in increased urine flow rate from 0.11 +/- 0.03 to 0.43 +/- 0.1 ml/min/kg, but had no effect on myocardial contractility, blood pressure, or cardiac rhythm. Furosemide IV to animals with steady-state therapeutic serum concentrations of digoxin (2.0 +/- 0.58 ng/ml) increased urine flow similarly but did not significantly alter serum digoxin concentration, blood pressure, myocardial contractility, or cardiac rhythm. Thus, contrary to some previous reports, furosemide does not interact with digoxin to produce an elevation in serum digoxin concentration or enhancement of the glycoside's myocardial action.