Significant Improvement in Digoxin Immunoassays Over Four Decades: Newer Assays are Less Affected by Interferences

Digitalis glycosides derived from foxglove plants have been used for medicinal purposes since the 16th century. Currently, digoxin derived from foxgloves is used clinically. Owing to the narrow therapeutic range, therapeutic drug monitoring is essential; however, digoxin immunoassays suffer from interference.

The issue of interference was reviewed for both older polyclonal antibody-based digoxin assays and newer monoclonal antibody-based digoxin assays. A literature search was conducted using PubMed, ScienceDirect, Scopus, Web of Science, and ResearchGate for studies on digoxin immunoassays published in the English language from 1969 to the present.

Radioimmunoassays for digoxin in the 1970s and, later, first-generation nonradioimmunoassay methods were liable to several interferences, including digoxin-like immunoreactive substances, spironolactone, potassium canrenoate, and various digoxin metabolites. However, for the last 10-15 years, next next-generation digoxin immunoassays have been virtually free from such interferences. Nevertheless, certain herbal supplements, as well as both Digibind and DigiFab, interfere with serum digoxin measurement, even with the more recently developed digoxin assays.

More recently introduced monoclonal antibody-based digoxin assays are superior to the older polyclonal antibody-based digoxin assays.