Spironolactone interference with digoxin radioimmunoassay in cirrhotic patients

The effects of spironolactone and cirrhosis on the measurement of serum digoxin levels by radioimmunoassay were studied in patients not receiving cardiac glycosides. Three groups of 10 patients each were studied. Groups 1 and 2 included patients with alcoholic cirrhosis, with Group 1 patients receiving spironolactone and Group 2 receiving no spironolactone. Group 3, the control group, included patients who were not receiving spironolactone and did not have cirrhosis. Apparent digoxin serum levels were measured by radioimmunoassay, and the mean levels of each group were compared. Group 1 had significantly higher apparent digoxin levels (1.3 +/- 0.62 ng/ml, p 0.05) than Groups 2 or 3. The apparent digoxin level of Group 2 (0.74 +/- 0.44 ng/ml) did not differ significantly from that of Group 3 (0.40 +/- 0.35 ng/ml). Significant correlations were found between apparent serum digoxin levels and daily spironolactone dose (Group 1), SGOT levels (Group 1), and prothrombin time/control ratios (Group 2 and all groups combined). Spironolactone appears to increase digoxin levels measured by radioimmunoassay. The effect of cirrhosis on digoxin radioimmunoassay has not been confirmed.