2025 Southeastern Residency Conference

Title: Determining the Therapeutic Dosage of Enoxaparin Anticoagulation Among Morbidly Obese Patients After the Implementation of an Automatic Clinical Pharmacy Anti-Xa Monitoring Service Using Enoxaparin Dosing Protocol
Authors: Kelsey Green, Michael Ezebuenyi, Jennifer Jones, Danielle Ricks, and Gregg Davis
Objective: The purpose of this study is to determine the required dose of enoxaparin in mg/kg to attain therapeutic anti-Xa levels in morbidly obese patients. 
Background: Enoxaparin is a low-molecular weight heparin (LMWH) used for prophylaxis and treatment of venous thromboembolism (VTE), acute coronary syndromes (ACS) and stroke prevention in atrial fibrillation. Most patients receiving LMWH do not need laboratory monitoring. However, monitoring anti-Xa levels in patients with morbid obesity is recommended due to variations in pharmacokinetic parameters which affect drug concentrations. Currently, there is no standardized dosing regimen for the morbidly obese patient population. 
Methods: This study is a single-center retrospective electronic chart review conducted from August 2021 to August 2024. This study has been approved by the Institutional Review Board at Our Lady of the Lake Regional Medical Center (OLORMC). The electronic medical record was used to identify eligible patients, which include adults with a BMI greater than or equal to 35 kilograms per square meter or total body weight greater than or equal to 150 kilograms who are initiated on treatment dosing of enoxaparin. OLOLRMC employs an automatic consult for a clinical pharmacist-driven anti-Xa protocol, which was implemented in 2019, for monitoring and adjusting enoxaparin doses for morbidly obese patients. Data was collected on the initial enoxaparin dose, initial anti-Xa levels, enoxaparin dose at goal anti-Xa level, the time (in days) to reach therapeutic anti-Xa level, length of hospitalization and the occurrence of adverse bleeding events. Descriptive statistics along with other relevant statistical tests, such as regression and correlation, will be utilized in the analysis of collected data. The primary outcome of the study is the required enoxaparin dose in mg/kg to attain two therapeutic anti-Xa levels. Subgroup analyses are planned to compare the doses of enoxaparin across BMI ranges, renal function, and different indications. 
Results: Overall, the enoxaparin dose at time of second consecutive therapeutic anti-Xa level was found to be 0.77 mg/kg (IQR 0.60, 0.84). The median time to attain two consecutive therapeutic anti-Xa levels was 154 hours (IQR 76, 221). Out of the patients weighing greater than or equal to 155 kg who had initial doses capped at 150 mg, had lower rates of supratherapeutic levels and improved time to two consecutive anti-Xa levels. In addition, one limitation of our study was 20% of anti-Xa levels were unable to be assessed due to being drawn outside of the peak window. 
Conclusion: In conclusion, lower initial enoxaparin doses of ~0.75 mg/kg and appropriate drawing times of anti-Xa levels would improve the ability and time to reach therapeutic anti-Xa levels in morbidly obese patients.