The Evaluation of Serum Digoxin Measurement Frequency In Patients Hospitalized In A University Hospital and Treated with Digoxin

Abstract

Therapeutic drug monitoring (TDM) for digoxin started nearly 50 years ago. However, inappropriate use of TDM for digoxin is still encountered despite so many years of practice. The aims of the study were to find out the frequency of serum digoxin concentration measurements, the rate of unnecessarily frequent measurements and the reasons for unnecessarily frequent measurements. This is a descriptive and a cross sectional study which evaluates the data of the patients who had been hospitalized between January 2011-December 2015, treated with oral digoxin. Patients who had more than one measurement of serum digoxin concentration were included in the study evaluation. When the time between consecutive measurements was less than 7 days, it was considered an “unnecessary measurement”. Descriptive statistical analysis was performed for serum digoxin measurement frequency, time between consecutive measurements, serum digoxin, potassium and creatinine levels, age, gender, diagnosis and the inpatient department. The chi-square, chi-square for trend and logistic regression analysis were used. We evaluated 2065 hospital admissions for 1621 patients and 11407 serum digoxin measurements. The time between consecutive serum digoxin concentration measurements was 1.9±2.4 days and 96.7% of all measurements were classified as unnecessary. While no correlation between patient age, gender, serum creatinine level and measurement frequency was found, unnecessary measurement frequency was high when potassium levels were within the normal range. Unnecessary measurement frequency increased when serum digoxin level exceeded 2 ng/mL. Unnecessary measurements were often performed in all departments with the highest frequency in coronary care unit and cardiology department. In our study, unnecessary serum digoxin measurement frequency was found to be very high although only one of the appropriateness criteria was evaluated. The findings reveal the need for a continuous medical education on TDM in order to plan a proper treatment and reduce unnecessary costs.