title: A comparative study of the effect of continuous combined conjugated equine estrogen plus medroxyprogesterone acetate and tibolone on blood coagulability.
abstract: BACKGROUND
  Hormone therapy (HT) after the menopause is associated with increased risk of venous thromboembolism (VTE). Tibolone has pharmacodynamic properties different from other hormone preparations. We compared the effect of a combined HT and tibolone on the inhibition of haemostasis.
  
  
  METHODS
  Thirty-eight post-menopausal women were randomly assigned to 1.25 or 2.5 mg per day of tibolone or oral continuous combined conjugated equine estrogen plus medroxyprogesterone acetate (CEE/MPA). Inhibitors of haemostasis were measured at baseline and after 12 months.
  
  
  RESULTS
  Results from the two groups of women receiving tibolone were not significantly different and, to improve the power of the study, the two groups were merged. Higher concentration of protein S (1.16 versus 1.00 IU ml(-1); P = 0.005) and higher activated protein C resistance ratio (APC-R) (4.2 versus 3.65; P = 0.04) were observed in the tibolone group than in the CEE/MPA group. Both doses of tibolone increased APC-R significantly (P < 0.01). Tissue factor pathway inhibitor (TFPI) was lower in the CEE/MPA group than in the tibolone group (67.8 versus 79.9 ng ml(-1); P = 0.03). CEE/MPA reduced the concentration of antithrombin (P = 0.002), protein S (P < 0.001) and TFPI (P < 0.001). Both preparations reduced the concentration of plasminogen activator inhibitor 1 (P < 0.05).
  
  
  CONCLUSIONS
  Tibolone induces fewer pharmacological alterations on blood coagulability than CEE/MPA and has a potentially favourable effect on APC-R. This may translate into a corresponding low risk of VTE, as also indicated from the existing clinical data.
authors.affiliation: Department of Obstetrics and Gynecology, Frederiksberg Hospital, University of Copenhagen, Denmark.
authors.forename: Sven O
authors.initials: SO
authors.lastname: Skouby
authors.forename: Johannes J
authors.initials: JJ
authors.lastname: Sidelmann
authors.forename: Lisbeth
authors.initials: L
authors.lastname: Nilas
authors.forename: Jørgen
authors.initials: J
authors.lastname: Jespersen
mesh_terms: D000368:Aged; D000818:Animals; D001777:Blood Coagulation; D020847:Estrogen Receptor Modulators / Q000008:administration & dosage; D004966:Estrogens, Conjugated (USP) / Q000008:administration & dosage*; D005260:Female; D006487:Hemostasis; D006736:Horses; D006801:Humans; D017258:Medroxyprogesterone Acetate / Q000008:administration & dosage*; D008875:Middle Aged; D009652:Norpregnenes / Q000008:administration & dosage*; D017698:Postmenopause; D013923:Thromboembolism / Q000209:etiology; D020246:Venous Thrombosis / Q000209:etiology
chemical_list: D020847:Estrogen Receptor Modulators; D004966:Estrogens, Conjugated (USP); D009652:Norpregnenes; D017258:Medroxyprogesterone Acetate; C027385:tibolone