Thromb Haemostasis
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Dabigatran is a reversible and selective, direct thrombin inhibitor (DTI) undergoing advanced clinical development as its orally active prodrug, dabigatran etexilate. This study set out to determine the molecular potency and anticoagulant efficacy of dabigatran and its prodrug dabigatran etexilate. This was achieved through enzyme inhibition and selectivity analyses, surface plasmon resonance studies, platelet aggregation, thrombin generation and clotting assays in vitro and ex vivo. ⋯ In vivo, dabigatran prolonged the aPTT dose-dependently after intravenous administration in rats (0.3, 1 and 3 mg/kg) and rhesus monkeys (0.15, 0.3 and 0.6 mg/kg). Dose- and time-dependent anticoagulant effects were observed with dabigatran etexilate administered orally to conscious rats (10, 20 and 50 mg/kg) or rhesus monkeys (1, 2.5 or 5 mg/kg), with maximum effects observed between 30 and 120 min after administration, respectively. These data suggest that dabigatran is a potent, selective thrombin inhibitor and an orally active anticoagulant as the prodrug, dabigatran etexilate.
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Randomized Controlled Trial Multicenter Study Comparative Study
Comparison of the pharmacokinetics of two von Willebrand factor concentrates [Biostate and AHF (High Purity)] in people with von Willebrand disorder. A randomised cross-over, multi-centre study.
Plasma-derived factor concentrates are important in the management of von Willebrand disorder (VWD). In our geographic locality, a single viral inactivation step concentrate (AHF [High Purity]), has been replaced with one using a double viral inactivation step (Biostate). The aim of this study was to compare the pharmacokinetics of von Willebrand factor (VWF) and factor VIII (FVIII) after administration of AHF (High Purity) and Biostate. ⋯ VWF:CB and VWF:RCo relative to VWF:Ag, level of HMW VWF relative to LMW-VWF) were determined to be higher for Biostate than AHF (High Purity). PFA-100 CTs did not adequately reflect changes in these VWF parameters. Based on these results, one would expect Biostate to be at least as effective, if not superior to AHF (High Purity) for the treatment of VWD.
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Meta Analysis
Rivaroxaban for thromboprophylaxis after orthopaedic surgery: pooled analysis of two studies.
Rivaroxaban (BAY 59-7939) is an oral, direct factor Xa inhibitor in clinical development for the prevention and treatment of venous thromboembolism (VTE). This analysis of pooled results from two phase II studies of rivaroxaban for VTE prevention after major orthopaedic surgery aimed to strengthen the conclusions of the individual studies. One study was conducted in patients undergoing total hip replacement (THR; N = 722), and one in patients undergoing total knee replacement (TKR; N = 621). ⋯ Major bleeding (safety population, n = 1,317) increased dose-dependently with rivaroxaban (p < 0.001), occurring in 0.9%, 1.3%, 2.1%, 3.9%, and 7.0% of patients receiving rivaroxaban total daily doses of 5, 10, 20, 40, and 60 mg, respectively, versus 1.7% of patients receiving enoxaparin. No routine coagulation monitoring was performed, and there were no significant differences between dose response relationships with rivaroxaban after THR and TKR. Overall, rivaroxaban total daily doses of 5-20 mg had the most favorable balance of efficacy and safety, relative to enoxaparin, for the prevention of VTE after major orthopaedic surgery.
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It is unknown whether strategies validated for diagnosing pulmonary embolism (PE) are valid in patients with a history of PE. It was the objective of this study to investigate whether a diagnostic algorithm consisting of sequential application of a clinical decision rule (CDR), a quantitative D-dimer test and computed tomography (CT) safely ruled out a clinical suspicion of acute recurrent PE. Data were obtained from a diagnostic outcome study of patients suspected of PE. ⋯ A CT was indicated in all other patients (192) and ruled out recurrent PE in 127 patients (54%). Only one patient with a negative CT had a fatal recurrent PE during follow-up (0.8%; 95%CI: 0.02-4.3). In conclusion, this prospective study demonstrates the safety of ruling out a clinical suspicion of acute recurrent PE by a simple diagnostic algorithm in patients with a history of PE.
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Comparative Study
Parnaparin, a low-molecular-weight heparin, prevents P-selectin-dependent formation of platelet-leukocyte aggregates in human whole blood.
Parnaparin, a low-molecular-weight heparin (LMWH), prevents platelet activation and interaction with polymorphonuclear leukocyte (PMN) in a washed cell system. The in-vitro effect of parnaparin was studied here on platelet-PMN aggregates formed with more physiologic approaches in whole blood, in parallel with unfractionated heparin and enoxaparin, another LMWH. Citrated blood from healthy subjects was stimulated: i) from passage through the "Platelet Function Analyzer" (PFA-100), a device that exposes blood to standardized high shear flow through collagen/ADP cartridges; ii) by collagen and ADP (2 and 50 mug/ml, respectively) added in combination under stirring in an aggregometer cuvette; iii) with recombinant Tissue Factor, to generate thrombin concentrations able to activate platelets without inducing blood clotting, or iv) the Thrombin Receptor Activating Peptide-6 (TRAP-6). ⋯ Platelet fibrinogen binding and PMN activation markers (fibrinogen binding, CD11b and CD40) were also prevented by parnaparin. These data extend in more physiological systems of platelet activation, the anti-inflammatory profile of parnaparin, previously reported in washed cells. The greater effect of parnaparin, as compared to the reference heparins, could be due to chemico-physical differences possibly unrelated to their anticoagulant effect.