Digoxin Loading Doses and Serum Digoxin Concentrations for Rate Control of Atrial Arrhythmias in Critically Ill Patients

Intravenous (IV) digoxin loading dose (LD) recommendations for rate control of atrial arrhythmias in critically ill patients are not well studied. When using digoxin in the setting of atrial fibrillation/atrial flutter (AF/AFL), a LD in either a fixed-dose regimen, weight-based dose, or pharmacokinetic-based calculation to target a serum digoxin concentration (SDC) of 0.8-1.5 ng/mL is recommended. The objective of this study was to assess the safety and effectiveness of digoxin LD used in critically ill patients for rate control of AF/AFL and to assess the SDC achieved. This single-center retrospective cohort study included patients, who received IV digoxin and had a SDC drawn. The primary endpoint was the median SDC achieved after a digoxin LD. Secondary outcomes included the frequency of SDCs ≥1.5 ng/mL and heart rate control. A total of 92 patients were included. The median total LD of digoxin for the entire cohort was 11 μg/kg (750 μg). For 61% of the cohort, the LD was distributed over 6-hour intervals. The median SDC after completion of the IV digoxin LD was 1.3 ng/mL (0.9-1.7). The incidence of supratherapeutic SDC was 36% for the total cohort. A target heart rate <110 beats per minute within 24 hours from digoxin LD was achieved in 60% of the cohort. In conclusion, a median total digoxin LD of 750 μg in critically ill patients with AF/AFL, targeting a SDC <1.5 ng/mL, may be considered for acute rate control, taking into account drug-drug interactions in the cardiac intensive care unit. Future studies are necessary to confirm our findings.