PSHP 2026 Residency Conference

Purpose: 
This study aims to evaluate real-world enoxaparin dosing and anti-Xa levels among patients with obesity to assess whether dose reductions improved the proportion of therapeutic anti-Xa levels and reduced supratherapeutic exposure.
 
Methods: 
This single-center retrospective chart review at Penn State Health Milton S. Hershey Medical Center evaluated adults with body mass index ≥35 kg/m2 receiving therapeutic enoxaparin every 12 hours with at least one appropriately timed anti-Xa level between June 2023 and June 2025. Therapeutic enoxaparin included standard weight-based dosing (1 mg/kg) using actual body weight with institutional syringe rounding, continuation of home regimen, or empiric dose adjustments based on body mass index or prior anti-Xa levels. Data collected included demographics, enoxaparin doses, anti-Xa levels, and bleeding events. The therapeutic anti-Xa range was defined as 0.5-1 IU/mL. The primary outcome was the proportion of patients requiring dose reduction based on anti-Xa levels. Secondary outcomes included percent dose reduction and bleeding events. Descriptive statistics and subgroup analyses by dosing group and obesity class were performed.
 
Results: 
Among 174 patients, 56% had supratherapeutic, 41% therapeutic, and 3% subtherapeutic initial anti-Xa levels. Lower initial doses (<0.85 mg/kg) were associated with higher therapeutic rates (64-65%) and lower supratherapeutic rates (18-32%) compared with >0.95 mg/kg (35% therapeutic, 65% supratherapeutic). Patients receiving <0.75 mg/kg had significantly lower odds of supratherapeutic levels (OR 0.11, p<0.001). The mean therapeutic dose was 0.84 mg/kg among all patients, however 0.81 mg/kg among those with class 3 obesity. Repeat anti-Xa monitoring occurred in 16% of patients with therapeutic anti-Xa levels, with 71% remaining therapeutic. Bleeding occurred in 6% of patients, with 82% of events in those with supratherapeutic levels.
 
Conclusion:
Reduced enoxaparin dosing (<0.85 mg/kg) in patients with obesity was associated with improved therapeutic anti-Xa levels and significantly lower supratherapeutic anti-Xa levels compared with standard dosing (>0.95 mg/kg). Supratherapeutic levels were common and linked to most bleeding events. These results support lower initial dosing and more targeted anti-Xa monitoring in patients with obesity.