Interferences
Digoxin-specific antibodiy fragments are an antidote that may be used to treat digoxin overdose. These fragments cross-react with the digoxin assay and will cause falsely elevated results. Serum digoxin levels cannot be used for monitoring purposes after the administration of these fragments.
Some physiological states, such as pregnancy, chronic kidney disease and chronic liver disease are associated with endogenous digoxin-like substances that cross-react with the digoxin assay and will cause falsely elevated results.
Additional Specimen Information
A trough sample should be collected (i.e. taken immediately before the next dose is due).
Drug levels should not be checked until steady state pharmacokinetics have been achieved (i.e. at least 4-5 half-lives after starting the drug/changing dose - the half-life of digoxin is approximately 36 hours, but may be significantly longer in those with renal impairment).
