The Use of Serum Digoxin Levels in Clinical Practice

THE need for an accurate and simple method of monitoring digitalis dosage is clearly evident from recent studies showing that 30% of patients admitted to a medical service had evidence of toxic effects from digitalis, while 11% of patients were "under-digitalized." Studies in experimental animals indicate that 60% of a lethal dose has been given when cardiac arrhythmias first appear, ie, at the point of maximal therapeutic effect. In addition, with the exception of the patient with atrial fibrillation in whom the ventricular rate usually can be used as a guide to further digitalis therapy, heretofore there has been no accurate, safe, and reliable clinical means to determine optimal digitalis therapy. To complicate matters further, there is no specific cardiac arrhythmia due to digitalis that cannot also be due to a patient's underlying heart disease. Hence, the clinician is often presented with the therapeutic choice of either increasing his patient's