Spironolactone as a source of interference in commercial digoxin immunoassays.
Eight commercial digoxin immunoassay methods were tested in 17 subjects taking spironolactone (but not digoxin) to evaluate cross-reactivity from parent drug and/or metabolites. Four of these methods showed significant (up to 1.9 nmol/L) and variable "apparent digoxin" concentrations, despite the absence of digoxin in the drug regimen. The results suggest that clinical laboratories require a knowledge of their method with respect to spironolactone-related cross-reactivity and should exercise caution when interpreting digoxin results where spironolactone is coadministered. Further, the presence of concurrent renal and/or hepatic impairment could delay clearance of spironolactone metabolites (as well as digoxin metabolites and endogenous substances) and further distort a genuine digoxin result.
D000328:Adult; D000368:Aged; D003429:Cross Reactions; D004077:Digoxin / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011863:Radioimmunoassay; D013148:Spironolactone / Q000097:blood*
D013148:Spironolactone; D004077:Digoxin