title: Anti-Xa effect of a low molecular weight heparin (dalteparin) does not accumulate in extended duration therapy for venous thromboembolism in cancer patients.
abstract: Many patients with venous thromboembolism are being treated with low molecular weight heparin for extended periods of time. It is not certain if it is necessary to assess anti-Xa levels for extended treatment periods. This study is a prospective assessment of anti-Xa levels in patients on long-term therapy for acute venous thromboembolism who have active cancer. Consecutive consenting patients from one center in a multicenter trial that compared 6 months of low molecular weight heparin with oral anticoagulant therapy were treated with therapeutic doses of dalteparin (200 IU per kilogram) subcutaneously daily. Anti-Xa levels were assessed at the end of weeks 1 and 4,4-6 hours after injection of dalteparin. Patients were followed for bleeding and recurrent venous thromboembolism. There were 24 patients who had anti-Xa levels measured at weeks 1 and 4. Two other patients had week 1 measurements performed but died before the week 4 sample was collected due to their underlying cancer. The mean anti-Xa levels at weeks 1 and 4 were 1.11 and 1.03 anti-Xa units/ml respectively (P=0.13). These results suggest that for patients with active cancer receiving extended duration therapy with low molecular weight heparin (dalteparin) there is no accumulation of anti-Xa effect over the first month of therapy. Monitoring of anti-Xa levels in this situation is usually not required.
authors.affiliation: London Health Sciences Centre, 800 Commissioners Road East, London, Ontario, N6A 4G5, Canada. michael.kovacs@lhsc.on.ca
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Kovacs
authors.forename: Mark N
authors.initials: MN
authors.lastname: Levine
authors.forename: Michael
authors.initials: M
authors.lastname: Keeney
authors.forename: Karen M
authors.initials: KM
authors.lastname: Mackinnon
authors.forename: Agnes Y
authors.initials: AY
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage*; D017985:Dalteparin / Q000008:administration & dosage*; D065427:Factor Xa Inhibitors; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000150:complications*; D011446:Prospective Studies; D013923:Thromboembolism / Q000097:blood / Q000150:complications* / Q000188:drug therapy*; D014859:Warfarin / Q000008:administration & dosage
chemical_list: D000925:Anticoagulants; D065427:Factor Xa Inhibitors; D014859:Warfarin; D017985:Dalteparin