Evaluation of therapeutic anticoagulation with enoxaparin and associated anti-Xa monitoring in patients with morbid obesity: a case series

Our purpose was to describe anti-Xa levels, dosage requirements, and complications associated with enoxaparin treatment doses in patients with morbid obesity. Inpatients with a BMI >40 kg/m 2 at an academic medical center prescribed therapeutic enoxaparin from 2004 to 2010 who also had an associated anti-Xa level were included in this retrospective evaluation. Twenty-six patients were identified having median weight of 162 kg (range 106–243), median BMI of 49.5 kg/m 2 (range 40.1–98.1), and median enoxaparin duration of 4 days (range 1–32). Venous thromboembolism was the most common reason for anticoagulation ( n = 19, 73%). The median starting dose was 0.8 mg/kg actual body weight (range 0.51–1; absolute dose 80–150 mg) every 12 h. Twelve patients (46%) achieved a goal anti-Xa level, 10 (38%) were above goal and 4 (15%) were uninterpretable. Among the 10 patients with anti-Xa levels above goal, the median initial dose was 0.85 mg/kg (range 0.75–1) versus 0.74 mg/kg (range 0.51–1) for patients at goal with similar median peak serum creatinine (PSCr) values between these two groups ( P > 0.05). No bleeding events occurred in patients achieving goal anticoagulation versus 4/10 (40%) with high anti-Xa levels ( P = 0.033) with similar median PSCr between these groups. No thrombotic events occurred while on therapy. The majority in this cohort with morbid obesity achieved anti-Xa levels at or above goal at doses less than the recommended 1 mg/kg every 12 h. Bleeding events were more frequent among patients with anti-Xa levels above goal, despite similar PSCr values.