title: Once versus twice daily LMWH for the initial treatment of venous thromboembolism.
abstract: BACKGROUND
  In the initial treatment of venous thromboembolism (VTE) low molecular weight heparin (LMWH) is administered once or twice daily. A once daily treatment regimen is more convenient for the patient and may optimise home treatment. However it is not clear whether a once daily treatment regimen is as safe and effective as a twice daily treatment regimen.
  
  
  OBJECTIVE
  The objective of this review was to compare the efficacy and safety of once daily administration to a twice daily administration of LMWH.
  
  
  METHODS
  Trials were identified through the Specialised Register of the Cochrane Peripheral Vascular Diseases Group (last searched May 2001), the Cochrane Controlled Trials Register (CCTR/CENTRAL) (last searched Issue 1, 2002), by hand-searching other relevant journals, by checking cross-references and through personal communication with experts.
  
  
  METHODS
  Randomised clinical trials in which a once daily treatment regimen with LMWH is compared to a twice daily regimen in the initial treatment of patients with venous thromboembolism.
  
  
  METHODS
  Two reviewers assessed trials on criteria for inclusion and extracted the data independently.
  
  
  RESULTS
  Five studies were included with a total of 1508 patients. The pooled data showed a statistically non-significant difference in recurrent venous thromboembolism between the two treatment regimens (OR 0.82; 0.49 - 1.39). A comparison of major haemorrhagic events (OR 0.77; 0.40 - 1.45) and mortality (OR 1.14; 0.62 - 2.08) also showed a statistically non-significant difference between the two treatment regimens.
  
  
  CONCLUSIONS
  Once daily treatment with LMWH is as effective and safe as twice daily treatment with LMWH. However, the 95% confidence interval implies that there is a possibility that the risk of recurrent VTE might be higher when patients are treated once daily. Hence the decision to treat the patient with a once daily regimen will depend on the evaluated balance between increased convenience and the potential for a lower efficacy.
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, Room J2-204, Academic Medical Center, University of Amsterdam, PO Box 22700, 1100 DE Amsterdam, Netherlands. c.j.vandongen@amc.uva.nl
authors.forename: C J
authors.initials: CJ
authors.lastname: van Dongen
authors.forename: M R
authors.initials: MR
authors.lastname: Mac Gillavry
authors.forename: M H
authors.initials: MH
authors.lastname: Prins
mesh_terms: D000925:Anticoagulants / Q000008:administration & dosage*; D004334:Drug Administration Schedule; D006470:Hemorrhage / Q000139:chemically induced; D006495:Heparin, Low-Molecular-Weight / Q000008:administration & dosage*; D006801:Humans; D011655:Pulmonary Embolism / Q000188:drug therapy; D016032:Randomized Controlled Trials as Topic; D013923:Thromboembolism / Q000188:drug therapy*; D020246:Venous Thrombosis / Q000188:drug therapy*
chemical_list: D000925:Anticoagulants; D006495:Heparin, Low-Molecular-Weight