Background and Importance Monitoring enoxaparin is not routine as per guidelines but is recommended in renal insufficiency and debated for extreme body weights and pregnancy.

Aim and Objectives This study aims to assess enoxaparin monitoring in hospitalised patients and identify variables that correlate with its efficacy.

Material and Methods A descriptive, single-centre, retrospective study was conducted. Hospitalised patients receiving therapeutic enoxaparin doses were included, with measurement of peak anti-Xa concentration between December 2021 and January 2023. Patients undergoing renal replacement therapies were excluded.

Demographic data, laboratory and clinical parameters, and enoxaparin-related details were collected. Obesity was defined as body mass index ≥30 kg/m². Multiple linear regression was used to analyse the relationship between anti-Xa concentration and different variables including enoxaparin dose, obesity, renal impairment (ClCr < 30mL/min), and critical status. Suggested peak target range for anti-Xa is 0.5–1.1 IU/mL. STATA/BE was used to assess their correlation with Pearson coefficient and determine the best predictor.

Results A total of 147 patients were included, with a mean±SD age of 68 years (±12.29), weight of 85.03 kg (±22.92), and a BMI of 29.64 kg/m² (±0.61). Among the study population, 64 patients (43.5%) were obese, 15 (10.2%) had renal impairment, and 78 (53.1%) were critical patients. Mean±SD enoxaparin dose was 0.93 mg/kg (±0.13), and no significant differences were observed between obese (0.91±0.15mg/kg) and non-obese (0.95±0.02 mg/kg) populations (p=0.104). Seventy-nine patients (53.7%) presented anti-Xa concentrations out of range; 36 of them (45.6%) were obese.

In the multiple regression analysis, we observed a statistically significant effect of enoxaparin dose (p<0.001) and obesity (p=0.007) in anti-Xa concentrations.

Using the final model, we found a good correlation between anti-Xa concentration and enoxaparin dose (p<0.001). Pearson coefficient of 0.56 was obtained for the non-obese population, while it was of 0.16 in the obese population.

Conclusion and Relevance In our study, we identified obesity as a variable that showed a significant effect on anti-Xa concentration. We confirmed the existence of a linear association between anti-Xa concentration and enoxaparin dose for the non-obese population. For the obese population, a poor correlation between anti-Xa concentration and enoxaparin was found suggesting the need for monitoring due to less predictable pharmacokinetics.

Conflict of Interest No conflict of interest.