title: Anti-Xa levels in bariatric surgery patients receiving prophylactic enoxaparin.
abstract: BACKGROUND
  Limited data exist regarding efficacy and dosing of low-molecular-weight heparins, including enoxaparin, for morbidly obese patients. Prophylactic doses of 30 to 60 mg every 12 h have been described in bariatric surgery patients with appropriate anti-Xa levels reported between 0.18 and 0.6 units/mL.
  
  
  METHODS
  Fifty-two laparoscopic gastric bypass or banding patients were enrolled. Patients were divided into two groups by the dose of enoxaparin that was given: Group 1--enoxaparin 30 mg every 12 hours--and Group 2--enoxaparin 40 mg every 12 h. Anti-Xa levels were obtained 4 h after the first and third doses. Levels between 0.18-0.44 units/mL were considered appropriate.
  
  
  RESULTS
  There were 19 patients (74% female, mean body mass index [BMI] 48.4 kg/m2) in Group 1 and 33 patients (82% female, mean BMI 48.5 kg/m2) in Group 2. In Group 1, anti-Xa levels were 0.06 and 0.08 units/mL after the first and third doses, respectively. In Group 2, anti-Xa levels were 0.14 and 0.15 units/mL after first and third doses, respectively (p = NS). There was a statistically significant difference in anti-Xa levels between Group 1 first dose and Group 2 first dose (p < 0.05) and between Group 1 third dose and Group 2 third dose (p < 0.05). Percentage of appropriate anti-Xa levels at first dose differed 0% vs. 30.8% (Group 1 vs. Group 2; p = 0.01) and at third dose 9.1% vs. 41.7% (Group 1 vs. Group 2; p = 0.155).
  
  
  CONCLUSIONS
  When prophylactic dose enoxaparin of 30 mg every 12 h was changed to 40 mg every 12 h in bariatric surgery patients, anti-Xa levels significantly increased with prophylactic dose enoxaparin in bariatric surgery patients. The percentage of appropriate levels also increased; however, more than half of the patients receiving 40 mg every 12 hours failed to reach therapeutic levels. No levels were supratherapeutic. Dosage of 40 mg every 12 h may not be sufficient for bariatric surgery patients.
authors.affiliation: Department of Pharmacy, Princeton Baptist Medical Center, Birmingham, AL, USA. browan22@gmail.com
authors.forename: Brea O
authors.initials: BO
authors.lastname: Rowan
authors.forename: David A
authors.initials: DA
authors.lastname: Kuhl
authors.forename: Marilyn D
authors.initials: MD
authors.lastname: Lee
authors.forename: David S
authors.initials: DS
authors.lastname: Tichansky
authors.forename: Atul K
authors.initials: AK
authors.lastname: Madan
mesh_terms: D000328:Adult; D000925:Anticoagulants / Q000627:therapeutic use*; D050110:Bariatric Surgery; D017984:Enoxaparin / Q000627:therapeutic use*; D015951:Factor Xa / Q000032:analysis*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009767:Obesity, Morbid / Q000150:complications; D054556:Venous Thromboembolism / Q000150:complications / Q000517:prevention & control*
chemical_list: D000925:Anticoagulants; D017984:Enoxaparin; D015951:Factor Xa