Current considerations in digoxin usage.

Basic considerations in biotransformation and pharmacodynamics are presented as a basis for understanding clinical usage. The role of polarity in determining a given glycoside's duration of action and extent of biotransformation is emphasized. The pharmacokinetics are summarized emphasizing the fact that digoxin is not completely absorbed by oral administration. The important relationship of serum digoxin levels to myocardial content and apparently to myocardial response is reviewed. This relationship and the development of precise methods for measurement of digoxin in serum provide the clinician with accurate means to assess myocardial tolerance for digoxin under diverse clinical circumstances. This review includes discussion of methods of digitalization, appropriate use of serum levels, apparent and real resistance to digoxin, and apparent and real sensitivity to digoxin. The limitations of serum levels as a precise guide to toxicity are analyzed. Finally, new developments in use of immunologic therapy for digoxin intoxication are presented.