The antibody is specific for digoxin, a cardiac glycoside derived from the foxglove plant. Digoxin is administered for the therapeutic treatment of heart conditions such as atrial fibrillation, atrial flutter and heart failure, an acts by inhibiting the Na+/K+ ATPase. However, the drug has a very narrow therapeutic index and can cause toxic side effects. The Fab fragment prepared from 26-10 that neutralises the activity of digoxin and can be used as an antidote in case of overdose of digitalis. Anti-digoxin monoclonal antibodies can also be used to measure serum levels of the drug as a guide to therapy, and are useful in the investigation of the kinetics of interaction between antibody and antigen.