Selection of Monoclonal Anti-Digoxin Antibodies Suitable for Monitoring of Cardiac Glycosides

Abstract

Digoxin is the third most commonly prescribed drug in the United States and is routinely monitored in clinical chemistry laboratories. Polyclonal antisera used so far in immunoassays for digoxin are not satisfactory and lead to poor precision and problems with standartization. Monoclonal antibodies would certainly be preferable because of high reproducibility and possibility of standartization which they ensure. Twenty two anti-digoxin monoclonal antibodies (Mabs) were selected by an absorption enzyme-linked immunosorbent assay (ELISA)and by treatment of antigen-antibody complex with potassium thiocyanate at the earliest stages of hybridoma growth. Dissociation constants of selected Mabs were determined by ELISA. Detection limit in this system was also assessed. Specificity of twelve antibodies with sufficiently high-affinity constants to detect therapeutic and subtherapeutic levels of digoxin was determined by cross-reactivity experiments with 25 steroid compounds - cardiac glycosides, digoxin metabolites, steroid hormones, spironolactone. On the basis of these data, Mabs suitable for monitoring of cardiac glycosides might be selected.