Limited evidence suggests that
digoxin levels may be increased by about 20% by
spironolactone, but because
spironolactone or its
metabolite, canrenone, can interfere with some
digoxin assay methods, the evaluation of this interaction is difficult. In one report,
radioimmunoassay (RIA) and affinity-column-mediated immunoassay
(ACMIA) were particularly affected by
spironolactone and its metabolites. Conversely, falsely low
digoxin readings with the AxSym microparticle
enzyme immunoassay (MEIA) assay method led to
digoxin overdose and
toxicity in one patient.
Monitor
digoxin effects and consider taking
digoxin levels. Adjust the dose as necessary. Measurement of free
digoxin levels or use of a chemiluminescent assay (CLIA) or turbidometric immunoassay for
digoxin has been reported to mostly eliminate interference.