title: Apixaban versus enoxaparin for thromboprophylaxis after hip replacement.
abstract: BACKGROUND
  There are various regimens for thromboprophylaxis after hip replacement. Low-molecular-weight heparins such as enoxaparin predominantly inhibit factor Xa but also inhibit thrombin to some degree. Orally active, specific factor Xa inhibitors such as apixaban may provide effective thromboprophylaxis with a lower risk of bleeding and improved ease of use.
  
  
  METHODS
  In this double-blind, double-dummy study, we randomly assigned 5407 patients undergoing total hip replacement to receive apixaban at a dose of 2.5 mg orally twice daily or enoxaparin at a dose of 40 mg subcutaneously every 24 hours. Apixaban therapy was initiated 12 to 24 hours after closure of the surgical wound; enoxaparin therapy was initiated 12 hours before surgery. Prophylaxis was continued for 35 days after surgery, followed by bilateral venographic studies. The primary efficacy outcome was the composite of asymptomatic or symptomatic deep-vein thrombosis, nonfatal pulmonary embolism, or death from any cause during the treatment period. Patients were followed for an additional 60 days after the last intended dose of study medication.
  
  
  RESULTS
  A total of 1949 patients in the apixaban group (72.0%) and 1917 patients in the enoxaparin group (71.0%) could be evaluated for the primary efficacy analysis. The primary efficacy outcome occurred in 27 patients in the apixaban group (1.4%) and in 74 patients in the enoxaparin group (3.9%) (relative risk with apixaban, 0.36; 95% confidence interval [CI], 0.22 to 0.54; P<0.001 for both noninferiority and superiority; absolute risk reduction, 2.5 percentage points; 95% CI, 1.5 to 3.5). The composite outcome of major and clinically relevant nonmajor bleeding occurred in 129 of 2673 patients assigned to apixaban (4.8%) and 134 of 2659 assigned to enoxaparin (5.0%) (absolute difference in risk, -0.2 percentage points; 95% CI, -1.4 to 1.0).
  
  
  CONCLUSIONS
  Among patients undergoing hip replacement, thromboprophylaxis with apixaban, as compared with enoxaparin, was associated with lower rates of venous thromboembolism, without increased bleeding. (Funded by Bristol-Myers Squibb and Pfizer; ClinicalTrials.gov number, NCT00423319.).
authors.affiliation: Department of Orthopedics, Spine Clinic, and Clinical Trial Unit, Hørsholm Hospital, University of Copenhagen, Hørsholm, Denmark. mirula@noh.regionh.dk
authors.forename: Michael Rud
authors.initials: MR
authors.lastname: Lassen
authors.forename: Alexander
authors.initials: A
authors.lastname: Gallus
authors.forename: Gary E
authors.initials: GE
authors.lastname: Raskob
authors.forename: Graham
authors.initials: G
authors.lastname: Pineo
authors.forename: Dalei
authors.initials: D
authors.lastname: Chen
authors.forename: Luz Margarita
authors.initials: LM
authors.lastname: Ramirez
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000009:adverse effects / Q000627:therapeutic use*; D019644:Arthroplasty, Replacement, Hip; D016001:Confidence Intervals; D004311:Double-Blind Method; D017984:Enoxaparin / Q000009:adverse effects / Q000627:therapeutic use*; D065427:Factor Xa Inhibitors; D005260:Female; D006470:Hemorrhage / Q000139:chemically induced / Q000453:epidemiology; D006801:Humans; D007279:Injections, Subcutaneous; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000517:prevention & control*; D011720:Pyrazoles / Q000009:adverse effects / Q000627:therapeutic use*; D011728:Pyridones / Q000009:adverse effects / Q000627:therapeutic use*; D016896:Treatment Outcome; D054556:Venous Thromboembolism / Q000517:prevention & control*; D055815:Young Adult
chemical_list: D000925:Anticoagulants; D017984:Enoxaparin; D065427:Factor Xa Inhibitors; D011720:Pyrazoles; D011728:Pyridones; C522181:apixaban