title: Managing transitions from oral factor Xa inhibitors to unfractionated heparin infusions.
abstract: OBJECTIVE
  Published evidence regarding the effects of oral factor Xa inhibitors on anticoagulation monitoring tests is reviewed with a focus on monitoring concerns that can arise during transitions to i.v. heparin therapy.
  
  
  CONCLUSIONS
  Assays that measure inhibition of factor Xa activity (i.e., anti-Xa assays) are widely used in U.S. institutions to monitor i.v. heparin therapy and, in some cases, for monitoring other types of anticoagulation therapy. Clinicians have raised concerns that the use of anti-Xa assays to monitor heparin levels in hospitalized patients who must be transitioned from oral factor Xa inhibitor therapy to i.v. unfractionated heparin (UFH) infusions could yield unquantifiable or inaccurate results, leading to unnecessary UFH dose reductions and potential treatment failures; the manufacturer labeling of oral factor Xa inhibitors (apixaban, edoxaban, and rivaroxaban) does not provide specific guidance on this issue. Results of a literature review indicated that residual effects of oral factor Xa inhibitor use can result in substantial interference with the currently available chromogenic anti-Xa assays but negligible to moderate effects on global coagulation assays, which measure activated partial thromboplastin time (aPTT) or prothrombin time. Therefore, during the transition from an oral factor Xa inhibitor to i.v. UFH therapy, it may be prudent to consider an aPTT assay for anticoagulation monitoring.
  
  
  CONCLUSIONS
  The use of oral factor Xa inhibitors appears to affect the accuracy of anti-Xa assay results, with results of global coagulation assays affected to a lesser degree.
authors.affiliation: Department of Pharmacy, Texas Health Presbyterian Hospital of Dallas, Dallas, TX. andrewfaust@texashealth.org.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Faust
authors.affiliation: Community Hospital of the Monterey Peninsula, Monterey, CA.
authors.forename: Dave
authors.initials: D
authors.lastname: Kanyer
authors.affiliation: Department of Pharmacy, University of Washington, Seattle, WA.
authors.forename: Ann K
authors.initials: AK
authors.lastname: Wittkowsky
mesh_terms: D000284:Administration, Oral; D000925:Anticoagulants / Q000008:administration & dosage* / Q000097:blood; D001777:Blood Coagulation / Q000187:drug effects / Q000502:physiology; D016903:Drug Monitoring / Q000379:methods; D057915:Drug Substitution / Q000379:methods*; D065427:Factor Xa Inhibitors / Q000008:administration & dosage* / Q000097:blood; D006493:Heparin / Q000008:administration & dosage* / Q000097:blood; D006801:Humans; D007262:Infusions, Intravenous; D011517:Prothrombin Time / Q000379:methods
chemical_list: D000925:Anticoagulants; D065427:Factor Xa Inhibitors; D006493:Heparin