(950) Digoxin Loading Dose Strategies and Supratherapeutic Levels in a Cohort of Critically Ill Patients

Introduction: Digoxin is a rate controlling option for atrial fibrillation with rapid ventricular response. Loading doses (LD) can be weight-based or fixed, with recommendations to dose-adjust when creatinine clearance (CrCl) < 15 mL/min, and to avoid in renal replacement therapies (RRT). The purpose of this study was to assess intravenous (IV) LD strategies and factors that impact serum digoxin concentrations (SDC).

Methods: We retrospectively reviewed intensive care unit (ICU) patients from January 2021, to September 2023 who received at least a single dose of IV digoxin. We excluded patients who had digoxin as a documented home medication or received for heart failure. Demographic data, renal function, total digoxin LD were collected in addition to SDC after load completion. Digoxin levels were included for analysis if they were collected between 6 and 12 hours after the LD, and SDC of 1.2 ng/mL or greater were considered to be supratherapeutic. Doses were classified as appropriate or inappropriate based on ideal body weight (IBW) and renal function.

Results: Of the 99 patients identified, 84 underwent analysis. Patients were mostly male (n=57, 68%), with a median age of 68 (IQR 58-73) years. Nineteen patients (23%) were on RRT or had a CrCl < 15 mL/min. Patients received a median LD of 9.3 (IQR 6.7-13.3) mcg/kg. Doses were considered too low, too high, and appropriate in 38%, 35%, and 27% of patients, respectively. Fifty patients had an evaluable SDC, with 23 (46%) having a supratherapeutic level which occurred more commonly in patients with a CrCl < 30 mL/min or on RRT compared to those without (48% vs. 7%, p < 0.05). There were significantly more patients with a level < 1.2ng/mL with a CrCl > 50 mL/min compared to patients with impaired renal function (74% vs. 30%, p < 0.05). A LD too high for renal function and IBW occurred in 7 patients (30%), all of which resulted in supratherapeutic levels. There were no serious adverse events (ADEs) attributed to digoxin administration.

Conclusions: The findings of this study suggest that digoxin LD are variable, and supratherapeutic digoxin levels were common, particularly in patients with impaired renal function. Higher thresholds, such as CrCl less than 30 mL/min could be considered for a dose adjustment. Despite supratherapeutic SDC, no ADEs were noted.