Evaluation of Prophylactic Enoxaparin Anti-Xa Levels in Individuals ≥150 kg

Optimal dosing of prophylactic enoxaparin for individuals ≥150 kg is unknown due to limited inclusion in previous studies.Estimate an optimal weight-based prophylactic enoxaparin dose for individuals ≥150 kg.This multicenter, retrospective study included ≥150 kg adult patients admitted to the hospital between January 2014 and April 2024, who received twice daily prophylactic enoxaparin (goal peak anti-Xa 0.2-0.4 IU/mL). At least one peak anti-Xa was required, obtained 3 to 5 hours after the 3rd consecutive dose. The primary outcome was the range of dosing that produced goal prophylactic peak anti-Xa following linear regression modeling. Secondary outcomes were hospital and intensive care unit (ICU)/progressive care unit (PCU) length of stay (LOS), in-hospital mortality, and VTE/bleed events within 72 hours after an eligible peak anti-Xa.A total of 311 encounters and 388 peak anti-Xa levels were assessed. Patients were 46 (37-55) years old, 53.1% were male, and weighed 183.3 kg (166.1-204.1) with a BMI of 61.3 kg/m² (54.8-69.4). Creatinine clearance was 179.6 mL/min (126.5-228.2) and patients received 4 doses (4-6) before peak anti-Xa, with a time between of 249 minutes (227-271). Linear regression modeling revealed a statistically significant correlation (r² = 0.27) between weight-based dose and peak anti-Xa (p < 0.0001). Enoxaparin 0.34 mg/kg (95% CI 0.33-0.36) twice daily was predicted to achieve a peak anti-Xa of 0.3 IU/mL. Hospital LOS was 8 days (4-15), ICU/PCU LOS was 8 days (4-14, n = 158), and only two patients (0.6%) died during hospitalization. One VTE event was observed. Our results suggest an appropriate empiric weight-based prophylactic enoxaparin dose for hospitalized patients ≥150 kg is 0.34 mg/kg twice daily.