Prevalence of Nonoptimal Serum Digoxin Concentrations in a Cohort of Patients with Heart Failure

A recent post-hoc analysis of the Digitalis Investigation Group trial provides evidence that serum digoxin concentrations between 0.5 and 0.8 ng/mL may be optimal in the management of heart failure (HF). Purpose To evaluate the appropriateness of digoxin concentrations in patients treated for HF. Methods Serum digoxin concentrations and any subsequent changes in digoxin dosing were evaluated for hospitalized patients. Serum concentrations between 0.5 and 0.8 ng/mL were considered optimal for HF management. Results Over the period of May to November 2003, 119 patient admissions were evaluated accounting for 192 serum digoxin measurements. Of these measurements, 118 (61.5%) met both post-distributional and steady-state concentration criteria. Thirty-five (29.7%) concentrations were within the optimal range for HF, while the remaining 83 (70.3%) were either too high or low. Of those considered to be within an optimal range, eight (22.9%) received subsequent digoxin dose adjustments. Of the 83 concentrations considered to be nonoptimal for HF, only 18 (21.7%) received subsequent dose adjustments. Conclusions This study reveals that digoxin serum concentrations frequently lie outside of the optimal range for the management of HF. Response to these nonoptimal values is often inadequate or incorrect, indicating that there may be a delay in applying recent evidence into clinical practice in the patient population evaluated in this study. There appears to be a need for education about the use of digoxin in HF and adjustment in the “normal” range of digoxin concentrations reported by laboratories.