refludan and Disease-Models--Animal

Limitations and contraindications of heparins and oral vitamin K antagonists have led to the development of new anticoagulant drugs over the last few years. Argatroban is an intravenous direct thrombin inhibitor currently indicated for the prophylaxis and treatment of thrombosis associated with heparin-induced thrombocytopenia (HIT) and for patients at risk of HIT undergoing percutaneous coronary intervention (PCI). The role of argatroban for the treatment of acute coronary syndrome (ACS) is under evaluation.. This article reviews the potential use of argatroban for the treatment of ACS and presents the pharmacokinetic data currently available. The authors also present the pharmacodynamic literature of agratroban in addition to highlighting the safety and tolerability of the drug.. Theoretically, argatroban's pharmacokinetics makes it an attractive alternative to heparin. Pharmacological advantages of argatroban over heparin include a more-predictable anticoagulant response and the absence of a risk of HIT. Furthermore, argatroban has a fast and predictable dose-dependent anticoagulant effect with low inter-individual variability. It is non-immugenic, not susceptible to degradation by proteases and it is cleared via the liver. These characteristics confer argotroban a different profile from other anticoagulants. Agatroban is an effective alternative for patients when heparin, lepirudin and bivalirudin cannot be used. Its utility in ACS and PCI in non-HIT patients has been evaluated but further studies are warranted to define its role in this context.

Topics: Acute Coronary Syndrome; Animals; Antithrombins; Arginine; Disease Models, Animal; Drug Evaluation; Heparin; Hirudins; Humans; Peptide Fragments; Percutaneous Coronary Intervention; Pipecolic Acids; Randomized Controlled Trials as Topic; Recombinant Proteins; Sulfonamides; Thrombocytopenia; Thrombosis

Heparin-induced thrombocytopenia (HIT), a drug-induced immunohaematological adverse reaction, is a rare but potentially very severe condition. The main problem for this complex syndrome is its recognition and management, which should be as early as possible to avoid the development of life-threatening complications. Most studies have reported heterogeneous populations of patients with other diseases that potentially induce thrombocytopenia. There is no gold standard diagnostic criteria, and we have established a score with anamnestic criteria that allows us to evaluate the likelihood of HIT. In clinical practice, the diagnosis is based on the analysis of clinical features and laboratory tests. Platelet aggregation test (PAT) and an ELISA test (heparin platelet-induced antibodies) are generally performed by expert laboratories to confirm the occurrence of HIT. In our experience, both tests are concordant in the majority of patients. PAT seems to correlate better with the clinical features while ELISA appears more specific. Regarding their limits, both are complementary in the determination of HIT diagnosis coupled to the clinical score system. The treatment often requires a multidisciplinary approach. Danaparoid (Orgaran) or lepirudin (Refludan) are the two alternative treatments for HIT patients with marketing approval. To avoid further exposure to heparin, every HIT patient should carry a written document that confirms the immunoallergy.

Topics: Animals; Anticoagulants; Chondroitin Sulfates; Dermatan Sulfate; Disease Models, Animal; Drug Combinations; Fibrinolytic Agents; Heparin; Heparitin Sulfate; Hirudin Therapy; Hirudins; Humans; Immunoassay; Platelet Activation; Recombinant Proteins; Thrombocytopenia

Edoxaban is a novel, potent and orally active direct Factor Xa (FXa) inhibitor under development for prophylaxis and treatment of thromboembolic diseases. Properties of dose response and margin of safety of anticoagulants are the key factors for a positive risk/benefit of novel oral anticoagulants.. To compare the dose response of antithrombotic effect and margin of safety between antithrombotic and hemorrhagic effects of edoxaban with conventional anticoagulants, unfractionated heparin (UFH), dalteparin (low molecular weight heparin), lepirudin, and warfarin in rat models of thrombosis and hemorrhage.. Rats were treated with edoxaban, UFH, dalteparin, and lepirudin by continuous intravenous (iv) infusion, or with oral warfarin for 4 days before inducing thrombosis or bleeding. Thrombosis was induced by inserting a platinum wire into the inferior vena cava for 60 minutes. Tail template bleeding time was measured after making an incision on the tail.. In rats, iv infusion of edoxaban inhibited venous thrombosis in a dose-dependent manner. The other anticoagulants also exerted dose-dependent antithrombotic effects. The slopes of the dose-response curves of edoxaban were significantly shallower than the slopes of UFH, dalteparin, and warfarin. At supratherapeutic doses, edoxaban prolonged bleeding time in a rat tail bleeding model. To determine bleeding risk, the margins between antithrombotic and bleeding-time prolongation were compared. The margins of safety of edoxaban were wider than those of UFH, dalteparin, lepirudin, and warfarin.. These results suggest that edoxaban may be more easily controlled and has the potential for a more positive risk/benefit ratio compared to conventional anticoagulants.

Topics: Animals; Anticoagulants; Disease Models, Animal; Dose-Response Relationship, Drug; Factor Xa Inhibitors; Heparin; Hirudins; Male; Pyridines; Rats; Rats, Wistar; Recombinant Proteins; Thiazoles; Thromboembolism; Warfarin

Myocardial ischemia/reperfusion (I/R) injury is partly mediated by thrombin. In support, the functional inhibition of thrombin has been shown to decrease infarct size after I/R. Several cellular responses to thrombin are mediated by a G-protein coupled protease-activated receptor 1 (PAR1).However, the role of PAR1 in myocardial I/R injury has not been well characterized. Therefore, we hypothesized that PAR1 inhibition will reduce the amount of myocardial I/R injury. After we detected the presence of PAR1 mRNA and protein in the rat heart by RT-PCR and immunoblot analysis,we assessed the potential protective role of SCH 79797, a selective PAR1 antagonist, in two rat models of myocardial I/R injury. SCH 79797 treatment immediately before or during ischemia reduced myocardial necrosis following I/R in the intact rat heart. This response was dose-dependent with the optimal dose being 25 microg/kg IV. Likewise, SCH 79797 treatment before ischemia in the isolated heart model reduced infarct size and increased ventricular recovery following I/R in the isolated heart model with an optimal concentration of 1 microM. This reduction was abolished by a PAR1 selective agonist. SCH 79797-induced resistance to myocardial ischemia was abolished by wortmannin, an inhibitor of PI3 kinase; L-NMA, a NOS inhibitor; and glibenclamide, a nonselective K(ATP) channel blocker. PAR1 activating peptide,wortmannin, L-NMA and glibenclamide alone had no effect on functional recovery or infarct size. A single treatment of SCH 79797 administered prior to or during ischemia confers immediate cardioprotection suggesting a potential therapeutic role of PAR1 antagonist in the treatment of injury resulting from myocardial ischemia and reperfusion.

Topics: Androstadienes; Animals; Cardiotonic Agents; Disease Models, Animal; Dose-Response Relationship, Drug; Enzyme Inhibitors; Glyburide; Hirudins; Male; Myocardial Infarction; Myocardial Reperfusion Injury; Myocardium; Nitric Oxide; Nitric Oxide Synthase; Oligopeptides; omega-N-Methylarginine; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Potassium Channel Blockers; Potassium Channels; Proto-Oncogene Proteins c-akt; Pyrroles; Quinazolines; Rats; Rats, Sprague-Dawley; Receptor, PAR-1; Recombinant Proteins; Research Design; RNA, Messenger; Signal Transduction; Thrombin; Time Factors; Ventricular Function, Left; Wortmannin

Upregulation of the activated Factor VII (FVIIa)/Tissue Factor complex, downregulation of natural anticoagulation pathways, and inhibition of fibrinolysis, are major contributors to coagulopathies associated with acute inflammation. Provision of FVIIa, and consequent downstream coagulation-related proteases, also stimulates further inflammatory changes, which can result in disseminated intravascular coagulation. Thus, the potential protective effects in vivo of a genetic-based reduction in FVII levels have been investigated in a murine model of acute inflammation, namely lipopolysaccharide (LPS)-induced lethal endotoxaemia. Mice with a total FVII deficiency do not survive the neonatal period. Therefore mice expressing low levels of FVII (FVII(tTA/tTA)), producing sufficient amounts of FVII for survival (approximately 5% of wild-type (WT) FVII), were employed to investigate in vivo pathways involved in the crosstalk between coagulation, inflammation, and survival, consequent to administration of a lethal dose of LPS. The FVII(tTA/tTA) mice presented with reduced mortality, coagulation, and inflammatory responses in comparison with similarly treated WT mice after administration of LPS. The attenuated inflammatory responses in FVII(tTA/tTA) mice were associated with downregulation of Egr-1 signalling. Administration, in vivo, of specific inhibitors of FXa and thrombin demonstrated that the inflammatory responses were unaltered in WT mice, but further reduced in FVII(tTA/tTA) mice. Therefore, a FVII deficiency enhances survival from lethal endotoxaemia both through attenuation of inflammatory responses that result directly from reduced FVIIa levels, and, indirectly, from downregulation of coagulation proteases downstream of the FVII-dependent cascade.

Topics: Ancrod; Animals; Anticoagulants; Antithrombin III; Biomarkers; Blood Coagulation; Disease Models, Animal; Down-Regulation; Early Growth Response Protein 1; Endotoxemia; Factor VII Deficiency; Factor Xa; Fibrinogen; Fondaparinux; Hirudins; Lipopolysaccharides; Male; Mice; Mice, Inbred C57BL; Neutrophils; Peptide Hydrolases; Polysaccharides; Recombinant Proteins; Signal Transduction; Thrombin

Many functions of the coagulation system have nonthrombotic effects. The indirect thrombin inhibitor heparin has been previously shown to be effective in limiting intimal hyperplasia (IH). We sought to study the effect of thrombin on IH by using two direct thrombin inhibitors (DTIs), argatroban and lepirudin. Sprague-Dawley rats underwent interposition vein grafting to the carotid artery. Vein grafts were treated with either saline (n = 6) or one of the two DTIs (n = 6 for both). At 30 days, the rats were sacrificed and vessels were perfusion fixed. Sections of the proximal carotid artery, graft, and both anastomoses were stained with both hematoxlyin/eosin and von Gieson's elastin stain. Sections were examined and compared for luminal area and intima-to-media (IM) ratio. The vessels treated with DTIs had less (p < 0.05) IH (IM ratio for proximal anastomosis: control 1.036 +/- 0.857, lepirudin 0.373 +/- 0.21, argatroban 0.182 +/- 0.118) and better lumen preservation than the control vessels (lumen area of proximal anastomosis: control 1.69 +/- 0.9, lepirudin 2.45 +/- 0.74, argatroban 2.81 +/- 0.78). There were no thromboses in the DTI-treated vessels. Dilatation of the graft segment was noted in the argatroban group. Thus, DTIs are effective at reducing IH in a small-animal model, suggesting that inhibition of thrombin has a protective role in IH. In addition, a difference of action between DTIs is suggested by the dilatation seen only in the argatroban-treated graft sections.

Topics: Anastomosis, Surgical; Animals; Carotid Artery, Common; Disease Models, Animal; Fibrinolytic Agents; Hirudins; Hyperplasia; Male; Models, Cardiovascular; Rats; Rats, Sprague-Dawley; Recombinant Proteins; Thrombin; Thrombosis; Tunica Intima; Veins

Topics: Animals; Clinical Trials as Topic; Disease Models, Animal; Endothelium, Vascular; Escherichia coli; Hirudins; Humans; Recombinant Proteins; Shiga Toxin; Thrombin

Cardiopulmonary bypass and surgical stress are accompanied by a systemic inflammatory response and activation of coagulation. Thrombin forms fibrin and activates platelets and neutrophils. Consequently, disseminated microthrombosis might increase capillary vascular resistance and thus impair reperfusion. We hypothesized that recombinant hirudin, a direct inhibitor of thrombin, could attenuate coagulation and enhance microvascular flow during reperfusion.. Twenty pigs undergoing 60 minutes of aortic clamping and 75 minutes of normothermic perfusion were randomized in a blinded setting to receive an intravenous bolus of recombinant hirudin (10 mg, 0.4 mg/kg; n = 10) or placebo (n = 10) 15 minutes before aortic declamping and then continued with an intravenous 135-minute infusion of recombinant hirudin (3.75 mg/h, 0.15 mg/kg) or placebo. Thrombin-antithrombin complexes, activated clotting times, and several hemodynamic parameters were measured before cardiopulmonary bypass, after weaning from cardiopulmonary bypass, and at 30, 60, 90, and 120 minutes after aortic declamping. Intramucosal pH and Pco(2) were measured from the luminal surface of ileum simultaneously with arterial gas analysis at 30-minute intervals.. Recombinant hirudin inhibited thrombin formation after aortic declamping; at 120 minutes, thrombin-antithrombin complexes levels (microg/L, mean +/- SD) were 75 +/- 21 and 29 +/- 44 (P <.001) for placebo and pigs receiving recombinant hirudin, respectively. When compared with the placebo group, pigs receiving recombinant hirudin showed significantly higher stroke volume, cardiac output, and lower systemic vascular resistance at 60 and 90 minutes after aortic declamping (P <.05). Based on arteriomucosal Pco(2) and pH differences, progressive worsening of intestinal microcirculatory perfusion occurred in the placebo group but not in the recombinant hirudin group.. Infusion of thrombin inhibitor recombinant hirudin during reperfusion was associated with attenuated postischemia left ventricular dysfunction and decreased vascular resistance. Consequently microvascular flow was improved during ischemia-reperfusion injury. Control of thrombin formation during reperfusion may be a feasible approach to improve oxygen delivery to reperfused vascular beds.

Topics: Animals; Anticoagulants; Blood Gas Analysis; Cardiopulmonary Bypass; Disease Models, Animal; Female; Hemodynamics; Hirudins; Intestines; Male; Manometry; Postoperative Complications; Random Allocation; Recombinant Proteins; Swine; Vascular Resistance