Evaluation of therapeutic and toxic levels of serum digoxin concentration: a cross-sectional study from a tertiary hospital.

Objective: Digoxin is a cardiac glycoside for treating heart failure and atrial fibrillation. Despite its limited therapeutic range and complex pharmacokinetic properties, this medication continues to be frequently prescribed. This study aimed to evaluate the serum digoxin concentration (SDC) at therapeutic, subtherapeutic, and toxic levels and explore the factors affecting these levels in patients receiving digoxin therapy for heart failure.

Patients And Methods: In this descriptive and cross-sectional study, the data were obtained from the electronic system of patients who presented to Afyonkarahisar Health Sciences University. For the SDC, the reference range was accepted as 0.5-0.9 ng/mL, and the upper limit was 2.0 ng/mL. The patient's demographic characteristics, comorbidities, and laboratory findings were evaluated. The Mann-Whitney U test, Chi-square test, and logistic regression analysis were used. p<0.05 was considered statistically significant.

Results: The data of 419 patients (mean age: 65.9±16.1 years, 68.5% women) were evaluated. The mean SDC was 1.11±1.01 ng/mL, and it was below 0.5 ng/mL in 24.3% of the patients, 0.5-0.9 ng/mL in 23.4%, 0.9-2 ng/mL in 41.3%, and over 2 ng/mL in 11.1%. Age, male gender, the presence of diabetes mellitus, and high HbA1c values were found to be associated with greater SDC levels, but this was not statistically significant. The presence of renal failure, elevated creatinine and magnesium levels, and potassium, sodium, and calcium levels outside the normal limits significantly increased the SDC. High creatinine and low/high potassium values significantly affected the detection of SDC at the toxic level.

Conclusions: The measurement of SDC levels holds significance not only in the monitoring of toxicity but also in ensuring adherence to the recommended therapeutic range during therapy. It is recommended to exercise caution in terms of risk factors such as age, kidney function test results, and blood electrolyte levels.