New advances in the assessment and treatment of digitalis toxicity.

The narrow margin between the therapeutic and toxic doses and serum levels of cardiac glycosides results in a high incidence of digitalis toxicity. This common problem has led to the development of methods for determining serum glycosides concentrations. It is clear that overlap of serum digoxin levels occurs between groups of patients with and without evidence of toxicity. In spite of these difficulties, use of serum digoxin measurement has been reported to be associated with a lower incidence of digitalis intoxication in clinical practice. When digitalis toxicity does develop, it is generally of two types: disturbances of impulse formation and disturbances of conduction. Therapeutic interventions may include antiarrhythmic drugs, pacemaker placement, and, in the most severe cases, administration of cardiac glycosides-specific antibodies. Recent studies have shown that monoclonal digoxin-specific antibodies and Fab fragments obtained by somatic cell fusion are effective in reversing advanced and otherwise lethal digoxin intoxication. The homogeneity of this antibody offers attractive possibilities for improving our ability to treat advanced digitalis intoxication safely and effectively.