Clinical utility of plasma digoxin measurements.

The results of plasma digoxin concentration (PDC) measurements in 260 patients treated with digitalis lanata preparations (digoxin, lanatoside C, betamethyl-digoxin) allowed the following observations: 1. Owing to an important overlap between "toxic" and "nontoxic" PDC values, the method has a limited value in the diagnosis of digitalis toxicity. However, in patients with toxicity associated with PDC under 2 ng/ml, it allows identification digitalis sensitivity. 2. A dosage selection based on PDC assessment led to a decrease of digitalis toxicity under 4%. As the method is not widely available, it has to be used in patients with borderline renal function, in aged subjects and in patients with rapid atrial fibrillation who require higher digitalis doses for heart rate control.