Thromboprophylaxis is a mainstay of hospital care in patients at high risk of thrombosis. Fixed doses of low-molecular-weight heparin (LMWH) are recommended for thromboprophylaxis in patients admitted to hospital for an acute medical condition. However, the distribution of LMWH is weight-based, and the efficacy of standard doses in obese patients may be decreased. Data for obese patients are mainly available in bariatric surgery with extremely obese patients who are at greater risk of venous thromboembolism than those hospitalized for a medical condition. We conducted a randomized control trial in medically obese inpatients (BMI≥30kg/m2) assessing two regimens of enoxaparin (40mg and 60mg SQ daily) in order to determine whether a stronger dosage would achieve higher anti-Xa level suitable for thromboprophylaxis. Between September 2013 and April 2015, 91 patients were included in the study (mean (±standard deviation) age was 70.4±10.7years, average BMI 37.8±6.4kg/m2). Main indications of thromboprophylaxis were mainly acute infection (50%), acute respiratory failure (10%), acute congestive heart failure (9%) and acute rheumatic disorders (18%). Average anti-Xa activity, measured 4h after the third administration of enoxaparin was 0.25±0.09IU/mL in group 1 (enoxaparin 40mg) and 0.35±0.13IU/mL in group 2 (enoxaparin 60mg) (P<10-3). The proportions of patients with normal anti-Xa activity (between 0.32 and 0.54IU/mL) were 31% (n=11) and 69% (n=24) in group 1 and 2 respectively (P=0.007). The proportions of anti-Xa activity measurement below the normal range were 64% and 36% in group 1 and 2 (P<10-3) respectively. Subgroup analysis focusing on high weight patients (above 100kg, n=45) showed a marked difference in the proportion of patients with normal anti-Xa activity between group 1 (9%) and 2 (44%) (P=0.009). No venous thromboembolism occurred during the study and one patient in group 1 died because of hemorrhagic shock due to a gastric ulcer. Incidence of adverse events was not different between the two groups (P=0.52). In conclusion, the ITOHENOX study shows in medically obese inpatients that thromboprophylaxis with enoxaparin 60mg provides higher control of anti-Xa activity, without more bleeding complications than the standard enoxaparin regimen. This trial is registered with ClinicalTrials.gov, number NCT01707732.
Keywords: Enoxaparin; Low-molecular weight heparin; Obesity; Special population; Thromboembolism prophylaxis; Weight-adapted regimen.
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