Immunopharmacological activity of monoclonal antidigitoxin.

A monoclonal antibody specific to digitoxin was developed and Fab fragments were prepared using the conventional papain method. The affinity constant was determined as 10(9)M-1 and the cross reactivity with digoxin was 2%. The Fab fragments were used for the reversal of acute digitoxin poisoning in rabbits (100% mortality). Fab fragments were administered over a 40 or 80 minute period just after digitoxin infusion. Rabbits treated with specific Fab fragments were protected by a bistoichiometrical dose. Evaluation of plasma digitoxin confirmed that the specific Fab fragments were able to extract and sequestrate digitoxin. The digitoxin-Fab fragment complexes were removed by renal excretion. Our data provide evidence of the benefit of monoclonal Fab fragments specific for digitoxin for the reversal of acute digitoxin poisoning.