Serum digoxin concentrations : a retrospective analysis

Abstract

The use of digoxin is limited by its narrow therapeutic index. American and European guidelines for the management of heart failure and atrial fibrillation recommend targeting a serum digoxin concentration (SDC) between 0.5 and 0.9ng/ml. The aim of the study was to retrospectively analyse SDCs and to assess compliance to the SDC target range recommended in the guidelines. SDCs recorded at the hospital Pathology laboratory between January 2008 and December 2017 were analysed according to gender, age, origin of request, specialty of referring physician and reason for request, and were compared to the SDC target range. Serum potassium (K+) levels and estimated glomerular filtration rate (eGFR) were analysed for SDCs recorded in 2017. A total of 19,065 SDCs from 6,107 patients (65% female, mean age 78 ± 11 years) were analysed. Mean SDC was 1.31 ± 1.01ng/ml (range <0.1-20.0ng/ml). Variations from the recommended SDC target range (0.5-0.9ng/ml) were: 32% within, 11% below and 57% above target range. Mean serum K+ level was significantly higher (p=0.020) in patients with SDC ≥ 2.0ng/ml (4.66 ± 0.66) compared to patients with SDC ≤ 0.9ng/ml (4.54 ± 0.73mEq/L). Mean eGFR was significantly lower (p<0.001) in patients with SDC >0.9ng/ml (66.76 ± 36.43) and ≥ 2.0ng/ml (64.39 ± 34.23) compared to patients with SDC ≤ 0.9ng/ml (73.84 ± 35.21mL/min/1.73m²). The mean SDC observed was higher than the upper limit of the recommended target SDC range. Further investigation to establish the clinical significance of the observed SDC findings on patient outcomes is warranted.