Therapeutic drug monitoring of digoxin, Serum levels and associated biochemical markers in a tertiary care laboratory

This study focuses on evaluating digoxin requests and their relationship with other laboratory tests, such as renal and liver function, and electrolytes in a city hospital. The study retrospectively analyzed therapeutic drug monitoring (TDM) requests for digoxin between February 1, 2024, and September 30, 2025. Parameters such as the age and sex of patients, requesting departments, and measurement results of digoxin, urea, creatinine, alanine aminotransferase (ALT), aspartate aminotransferase, sodium, potassium, chloride, calcium (Ca), magnesium, albumin, and total protein were assessed. Digoxin levels were classified into 3 groups: subtherapeutic (<0.8 ng/mL), therapeutic (0.8–2.0 ng/mL), and supratherapeutic (>2.0 ng/mL). A total of 237 digoxin TDM requests were retrieved. Of these, 72.8% were female. Internal Medicine accounted for the highest proportion of TDM requests (35.3%), followed by other departments (27.6%) and intensive care units (12.5%). According to digoxin concentration levels, subtherapeutic values were lower than therapeutic and supratherapeutic groups for age, urea, and creatinine ( P  ≤ .001). Subtherapeutic group values were higher than therapeutic and supratherapeutic groups for ALT ( P  = .01 for subtherapeutic-therapeutic and P  = .029 for therapeutic-supratherapeutic groups), albumin ( P  ≤ .001 for subtherapeutic-therapeutic and P  = .004 for subtherapeutic-supratherapeutic), and total protein ( P  = .002 for subtherapeutic-therapeutic and P  = .015 for subtherapeutic-supratherapeutic). There was a statistical difference in the subtherapeutic-supratherapeutic group ( P  = .01) and the therapeutic-supratherapeutic group ( P  = .001) for Ca. Our study shows that treatment with digoxin needs to be evaluated with comprehensive laboratory tests, including urea, creatinine, ALT, albumin, total protein, and Ca.