hirudin and Venous-Thrombosis

Heparin-induced thrombocytopenia (HIT) is a prothrombotic disorder characterized by heparin-dependent antibodies that activate platelets (PLTs) via PLT FcγIIa receptors. "Autoimmune" HIT (aHIT) indicates a HIT subset where thrombocytopenia progresses or persists despite stopping heparin; aHIT sera activate PLTs strongly even in the absence of heparin (heparin-independent PLT-activating properties). Affected patients are at risk of severe complications, including dual macro- and microvascular thrombosis leading to venous limb gangrene. High-dose intravenous immunoglobulin (IVIG) offers an approach to interrupt heparin-independent PLT-activating effects of aHIT antibodies.. A 78-year-old male who underwent cardiopulmonary bypass for aortic dissection developed aHIT, disseminated intravascular coagulation, and deep vein thrombosis; progression to venous limb gangrene occurred during partial thromboplastin time (PTT)-adjusted bivalirudin infusion (underdosing from "PTT confounding"). Thrombocytopenia recovered with high-dose IVIG, although the PLT count increase began only after the third dose of a 5-day IVIG regimen (0.4 g/kg/day × 5 days). We reviewed case reports and case series of IVIG for treating HIT, focusing on various IVIG dosing regimens used.. Patient serum-induced PLT activation was inhibited in vitro by IVIG in a dose-dependent fashion; inhibition of PLT activation by IVIG was much more marked in the absence of heparin versus the presence of heparin (0.2 U/mL). Our literature review indicated 1 g/kg × 2 IVIG dosing as most common for treating HIT, usually associated with rapid PLT count recovery.. Our clinical and laboratory observations support dose-dependent efficacy of IVIG for decreasing PLT activation and thus correcting thrombocytopenia in aHIT. Our case experience and literature review suggests dosing of 1 g/kg IVIG × 2 for patients with severe aHIT.

Topics: Aged; Aortic Aneurysm; Aortic Dissection; Cardiopulmonary Bypass; Cells, Cultured; Disease Progression; Gangrene; Heparin; Hirudins; Humans; Immunoglobulins, Intravenous; Male; Partial Thromboplastin Time; Peptide Fragments; Purpura, Thrombocytopenic, Idiopathic; Recombinant Proteins; Venous Thrombosis

Anticoagulant drugs belong to the group of antithrombotic agents and are successfully used in the prophylaxis and treatment of thromboembolic disorders. The use of anticoagulants in the prevention of deep venous thrombosis has significantly lowered the risk of venous thrombosis and fatal pulmonary embolisms even in high-risk situations such as orthopedic surgery. Anticoagulants play a central role in the treatment of acute venous thrombosis and in the prevention of recurrent events. Long-term anticoagulation therapy with orally active anticoagulants significantly reduces the risk of thromboembolic complications in patients showing cardiac arrhythmias. Whereas a few years ago heparins and vitamin K antagonists were the dominant anticoagulants, today a wide range of anticoagulants with improved pharmacological profiles are available. It remains an open question whether these new anticoagulants will improve the efficacy, safety, and acceptance of anticoagulant treatment approaches.

Topics: Administration, Oral; Anticoagulants; Antithrombins; Arginine; Arrhythmias, Cardiac; Blood Coagulation Tests; Factor Xa Inhibitors; Hemorrhage; Heparin; Heparinoids; Hirudins; Humans; Infusions, Intravenous; Orthopedic Procedures; Peptide Fragments; Pipecolic Acids; Postoperative Complications; Pulmonary Embolism; Recombinant Proteins; Risk Factors; Secondary Prevention; Sulfonamides; Thromboembolism; Treatment Outcome; Venous Thrombosis; Vitamin K

The standard multipotent anticoagulants (unfractionated and low molecular weight heparins, antagonists of vitamin K) are commonly used for treatment and/or prophylaxis of different thrombotic complications, such as deep vein thrombosis, thrombophilia, pulmonary embolism, myocardial infarction, stroke and so on. Advantages and shortcomings of these anticoagulants are considered. The modern tendencies to use small selective direct inhibitors of thrombin or factor Xa are surveyed. The search of the new targets in the coagulation cascade for development of new promising anticoagulants and improvement in antithrombotic therapy is discussed.

Topics: Anticoagulants; Benzimidazoles; beta-Alanine; Blood Coagulation; Dabigatran; Factor Xa; Factor Xa Inhibitors; Heparin, Low-Molecular-Weight; Hirudins; Humans; Platelet Aggregation Inhibitors; Thrombin; Thromboembolism; Thrombophilia; Venous Thrombosis; Vitamin K; Warfarin

Incidence of deep vein thrombosis in critically ill patients depends on the underlying disease but may be as high as 60%. The Surviving Sepsis Campaign clearly recommends administering anticoagulation in the absence of specific contraindications in patients with severe sepsis or septic shock. The article discusses risk factor for thromboembolic events in critical illness as well as means of non-pharmacologic and pharmacologic thrombosis prophylaxis. Peripheral vasoconstriction, edema, shock, and administration of catecholamines may reduce the bioavailability and efficacy of subcutaneous administration of low molecular weight heparin. This article further elaborates on the problem and pathophysiology of heparin resistance. Continuous intravenous administration of new anticoagulants may be a promising alternative to indirect anticoagulants. Severity of illness and SAPS II-score determine dosing of the direct thrombin inhibitor argatroban which needs to be about 10-times lower than in patients without critical illness.

Topics: Anticoagulants; Arginine; Biological Availability; Chromosome Breakage; Chromosome Disorders; Critical Care; Dose-Response Relationship, Drug; Drug Resistance; Heparin; Heparin, Low-Molecular-Weight; Hirudins; Humans; Infusions, Intravenous; Injections, Subcutaneous; Pipecolic Acids; Recombinant Proteins; Risk Factors; Sepsis; Severity of Illness Index; Shock, Septic; Sulfonamides; Thrombin; Thrombocytopenia; Venous Thrombosis

Direct thrombin inhibitors (DTIs) are an emerging class of anticoagulants in routine clinical practice, although they have been under investigation for quite some time. Desirudin (Iprivask®, Canyon Pharmaceuticals™) is a recombinant hirudin derivative that directly inhibits free and fibrin-bound thrombin. Desirudin was the first DTI approved for deep vein thrombosis (DVT) prophylaxis in Europe (Revasc®) and is the newest injectable DTI commercially available in the USA. Desirudin is one of the few nonheparin subcutaneous drugs that has demonstrable efficacy for DVT prophylaxis. Subcutaneous desirudin has been shown to be more effective than both subcutaneous unfractionated heparin and enoxaparin, with comparable bleeding rates in the prevention of DVT in patients undergoing elective hip replacement. Desirudin also offers the advantage of a fixed dosing regimen while being less immunogenic than unfractionated heparin. However, owing to its pharmacokinetic properties, patients with renal dysfunction require dosing modifications. The favorable profile shown with desirudin thus far will allow its clinical use to grow and will promote further investigation into broadening its clinical applications.

Topics: Animals; Anticoagulants; Antithrombins; Dose-Response Relationship, Drug; Hemorrhage; Hirudins; Humans; Recombinant Proteins; Renal Insufficiency; Venous Thrombosis

Topics: Acute Disease; Angioplasty, Balloon, Coronary; Anticoagulants; Arginine; Atrial Fibrillation; Azetidines; Benzylamines; Clinical Trials as Topic; Coronary Disease; Heparin; Hirudins; Humans; Myocardial Infarction; Peptide Fragments; Pipecolic Acids; Recombinant Proteins; Sulfonamides; Syndrome; Thrombin; Thromboembolism; Thrombosis; Venous Thrombosis

For patients with heparin-induced thrombocytopenia (HIT), reexposure to heparin is generally not recommended. However, these patients are likely to require anticoagulation therapy at some point in the future. During acute HIT, when thrombocytopenia and anti-heparin-platelet factor 4 antibodies (or HIT antibodies) are present, therapy with heparin must be avoided. In patients with subacute HIT, when platelets have recovered but HIT antibodies are still present, therapy with heparin should be avoided. In patients with a remote history of HIT, when HIT antibodies have cleared, heparin reexposure may be safe, although recurrent HIT has been described in some patients. For all of these patients, the use of alternate anticoagulant agents, including direct thrombin inhibitors and anti-Xa agents, is preferable. There is an increasing amount of data supporting the use of these alternative agents in a wide variety of clinical circumstances, including thromboprophylaxis and treatment of acute thrombosis. Except for a few clinical situations, it is generally possible to avoid heparin reexposure in patients with a history of HIT.

Topics: Angina, Unstable; Antibodies; Anticoagulants; Chondroitin Sulfates; Dermatan Sulfate; Drug Combinations; Female; Fondaparinux; Heparin; Heparitin Sulfate; Hirudins; Humans; Male; Multiple Organ Failure; Platelet Factor 4; Polysaccharides; Pregnancy; Preoperative Care; Recombinant Proteins; Thrombin; Thrombocytopenia; Venous Thrombosis

Unfractionated heparin, derived from porcine intestine, is the prototype of a rapidly acting anticoagulant. It has been used for over 60 years to arrest or prevent thrombus growth. Low-molecular-weight heparins, available in the last 20 years, are manufactured from unfractionated heparin and have superior dose-response relationships because of fewer nonspecific reactions with plasma proteins and cells. Fondaparinux is a recently approved five-saccharide synthetic molecule that carries the evolution of heparin further. It is a pure Xa inhibitor, with minimal nonspecific interactions. It does not appear to elicit the antibody that leads to heparin-induced thrombocytopenia (HIT). All of these agents are given either intravenously or subcutaneously. They act indirectly by activating the natural plasma inhibitor, antithrombin III. Direct thrombin inhibitors bind directly to thrombin's active site without interaction with the cofactor, antithrombin III. Lepirudin (Refludan; Berlex, Wayne, NJ) and argatroban (Argatroban; GlaxoSmithKline, Research Triangle Park, NC) are given intravenously and are usually used in HIT and thrombosis associated with HIT. Bivalirudin (Angiomax; The Medicines Company, Parsippany, NJ) is a parenteral direct thrombin used in place of heparin in percutaneous coronary interventions. Ximelagatran (Exanta; AstraZeneca, Wilmington, DE) is an oral direct thrombin inhibitor under development for both acute and chronic anticoagulation.

Topics: Anticoagulants; Arginine; Azetidines; Benzylamines; Embolism; Enzyme Inhibitors; Fondaparinux; Heparin; Heparin, Low-Molecular-Weight; Hirudins; Humans; Peptide Fragments; Pipecolic Acids; Polysaccharides; Recombinant Proteins; Sulfonamides; Thrombin; Thrombocytopenia; Venous Thrombosis

Current antithrombotic agents include anticoagulants (unfractionated and low-molecular-weight heparin, and antivitamin K) and platelet aggregation inhibitors (aspirin, ticlopidine, clopidogrel). Two areas are under particular investigation: specific inhibition, direct or indirect, of factor Xa and factor IIa. Pentasaccharide, an indirect anti-Xa, has proved effective in curing deep-vein thrombosis and more effective than enoxaparin for prophylactic treatment after orthopedic surgery. Administered in a single subcutaneous injection daily, it has no risk of thrombocytopenia; laboratory surveillance is based on anti-Xa activity. Hirudin and melagatran act by direct thrombin inhibition. Unlike hirudin (which requires monitoring of active coagulation time or ecarin clotting time), melagatran requires no laboratory monitoring. It is not associated with an increased risk of hemorrhage. But there is no true antidote at this time. If its efficacy is confirmed, ximelagatran, the orally active prodrug of melagatran, may facilitate the long-term treatment now reserved for antivitamin K. Three antagonists of the tissue factor-factor VIIa complex are also under development: rNAPc2 (Recombinant Nematode Anticoagulant Protein C2), ASIS (Active Site Inhibitor Factor Seven) and recombinant TFPI (Tissue Factor Pathway Inhibitor). Antiplatelet drugs are the reference antithrombotic agents for the prevention and treatment of arterial thrombosis. Aspirin remains in first place (75 to 300 mg/d) but the modest superiority of the thienopyridines (clopidogrel and ticlopidine) is established. Hemogram monitoring is no longer necessary for clopidogrel. Use of aspirin + a thienopyridine after placement of a coronary stent has been validated. Laboratory monitoring of antiplatelet treatments has not been codified.

Topics: Administration, Oral; Angioplasty, Balloon, Coronary; Anticoagulants; Aspirin; Azetidines; Benzylamines; Clopidogrel; Fibrinolytic Agents; Glycine; Hirudins; Humans; Injections, Subcutaneous; Platelet Aggregation Inhibitors; Polysaccharides; Prodrugs; Randomized Controlled Trials as Topic; Stents; Thrombosis; Ticlopidine; Time Factors; Venous Thrombosis

Lepirudin (Refludan), Berlex Laboratories, USA and Canada; Pharmion, all other countries), a recombinant derivative of the naturally occurring leech anticoagulant hirudin, was the first direct thrombin inhibitor to be approved by the European Agency for the Evaluation of Medicinal Products and the US Food and Drug Administration for the treatment of heparin-induced thrombocytopenia. Since its introduction into Europe and the USA, it has been studied in over 7000 patients requiring anticoagulation in conditions including acute coronary syndromes, percutaneous coronary intervention, cardiopulmonary bypass and heparin-induced thrombocytopenia. Three European clinical trials, designated Heparin-Associated Thrombocytopenia (HAT)-1, -2 and -3, demonstrated the efficacy and safety of lepirudin in the prevention and treatment of thrombosis in patients with antibody-confirmed heparin-induced thrombocytopenia. A postmarketing, observational study, termed the Drug-Monitoring Program, evaluated lepirudin in over 1000 patients with heparin-induced thrombocytopenia in the setting of routine clinical practice. In the Drug-Monitoring Program, adverse events were substantially reduced compared with clinical trials, while clinical efficacy was maintained; suggesting that insight gained through clinical experience was translated into improved safety. Here, pharmacotherapy using lepirudin is reviewed, with particular reference to clinical studies in heparin-induced thrombocytopenia, and some recommendations based on this extensive clinical experience with lepirudin are provided. Although only approved for the treatment of heparin-induced thrombocytopenia, the use of lepirudin in acute coronary syndromes, percutaneous coronary intervention, vascular surgery and coronary artery bypass grafting is also discussed. The review concludes with a discussion of pharmacokinetic and clinical data supporting the potential for subcutaneous administration of lepirudin.

Topics: Anticoagulants; Cardiovascular Surgical Procedures; Coronary Disease; Dose-Response Relationship, Drug; Heparin; Hirudins; Humans; Myocardial Infarction; Postoperative Complications; Recombinant Proteins; Thrombin; Thrombocytopenia; Venous Thrombosis

Native hirudin is the most potent natural direct thrombin inhibitor currently known; it is capable of inhibiting not only fluid phase, but also clot-bound thrombin. Recombinant technology now allows production of recombinant hirudins (r-hirudins), which are available in sufficient purity and quantity with essentially unaltered thrombin-inhibitory potency. As thrombin is known to play a key role in a number of thrombotic disorders, numerous studies focused on the impact of r-hirudins on the clinical course in these diseases. R-hirudins provided significantly more stable anticoagulation than standard heparin, but demonstrated a relatively narrow therapeutic range with relevant bleeding risk even at clinically effective doses. In doses that are not associated with an increased bleeding risk, r-hirudins often failed to demonstrate significant superiority to heparin. To date, r-hirudins have a definite role in the treatment of heparin-induced thrombocytopenia, where they markedly reduce the high risk of thrombosis. For prophylaxis of deep vein thrombosis, r-hirudins have been shown to be superior to both unfractionated and low molecular weight heparin, but are not extensively used in this indication. In acute coronary syndromes, a definite role of r-hirudins has not yet been firmly established. When applied in an appropriate dose as adjunct to thrombolysis in patients with acute myocardial infarction, randomized, controlled trials did not show a consistent benefit of r-hirudins, especially in the long-term. In patients undergoing coronary balloon angioplasty for acute coronary syndromes, promising effects in the early postprocedural phase did not translate to an improved outcome after 6 months. In patients with unstable angina pectoris, efficacy and safety of r-hirudins as primary antithrombotic therapy are still under debate. In the future, r-hirudins are to be compared with alternative or additional potent antithrombotic agents or treatment strategies. This comparison will ultimately lead to their final placement in the management of thrombotic disorders.

Topics: Clinical Trials as Topic; Coronary Disease; Fibrinolytic Agents; Heparin; Hirudins; Humans; Kidney Failure, Chronic; Partial Thromboplastin Time; Recombinant Proteins; Thrombin; Thrombocytopenia; Tissue Distribution; Venous Thrombosis

This review deals with a newly-developed category of antithrombotic drugs - the direct thrombin inhibitors. These agents interact with thrombin and block its catalytic activity on fibrinogen, platelets and other substrates. Heparin and its derivatives (low molecular weight heparins and the active pentasaccharide) inhibit thrombin and/or other coagulation serine proteases indirectly via antithrombin, and the warfarin-type drugs interfere with the synthesis of the precursors of the coagulation serine proteases. The direct thrombin inhibitors approved for clinical use at present (lepirudin, desirudin, bivalirudin, argatroban) and another in the advanced clinical testing stage (melagatran/ximelagatran), are the subject of this review. The chemical structure; kinetics of thrombin inhibition; pharmacokinetics and clinical use of each of these is discussed.

Topics: Antithrombins; Arginine; Coronary Disease; Half-Life; Hirudins; Humans; Metabolic Clearance Rate; Peptide Fragments; Pipecolic Acids; Recombinant Proteins; Sulfonamides; Thrombin; Venous Thrombosis

Topics: Ancrod; Anticoagulants; Antithrombins; Blood Coagulation; Fibrinolytic Agents; Forecasting; Heparin; Hirudin Therapy; Hirudins; Platelet Aggregation Inhibitors; Thromboembolism; Thrombolytic Therapy; Venous Thrombosis

This prospective pharmacoeconomic study analyses and discusses the cost effectiveness (expressed as cost per life-year gained) of desirudin in comparison with a low molecular weight heparin (LMWH), enoxaparin, as prophylaxis against deep vein thrombosis (DVT) in total hip replacement.. The cost effectiveness was analysed on the basis of results from a clinical trial that compared the recombinant hirudin, desirudin, with the LMWH, enoxaparin. The trial results regarding the incidence of DVT are included together with epidemiological data in a decision tree, simulating long term cost effectiveness of patients undergoing elective hip replacement. The model includes Markov processes simulating patients up to the age of 85 years, including the costs of DVT-related long term complications.. The average total thrombosis-related cost per patient under prophylactic therapy with enoxaparin is 7,022 Swedish kronor (SEK) compared with SEK7,497 when using desirudin (1998 values). The total costs with desirudin are 7% higher. Prophylaxis with desirudin in those patients undergoing elective hip replacement surgery adds, on average, 7 days of life per patient when compared with treatment using enoxaparin. This is equivalent to 1.91 additional years of life per 100 patients treated. The incremental cost-effectiveness ratio of prophylaxis with desirudin in patients undergoing elective hip replacement surgery is SEK24,864 per life-year gained in comparison with enoxaparin.. The present study demonstrates that prophylactic therapy with desirudin is a cost-effective approach for the prevention of DVT in patients undergoing total hip replacement.

Topics: Aged; Anticoagulants; Arthroplasty, Replacement, Hip; Cost-Benefit Analysis; Decision Trees; Economics, Pharmaceutical; Heparin, Low-Molecular-Weight; Hirudin Therapy; Hirudins; Humans; Postoperative Complications; Recombinant Proteins; Venous Thrombosis

At present, unfractionated heparin (UFH) and low molecular weight heparins (LMWHs) are used extensively for the prophylaxis and treatment of venous thromboembolism (VTE) and in most cases represent the agents of choice for these indications. However, both UFH and LMWHs have biophysical limitations. Over the past years, the progress in molecular biology and biotechnology has stimulated growing interest in hirudin, the most potent known natural inhibitor of thrombin. The biological properties of hirudin combined with its ready availability as recombinant forms make this drug well-suited for use as an anticoagulant agent. Available studies indicate that hirudin is significantly more effective for prophylaxis of VTE after total hip replacement than is either UFH or enoxaparin. Only limited data are available on its efficacy in the treatment of deep vein thrombosis. Moreover, hirudin is effective in the management of patients with heparin-induced thrombocytopenia (HIT) who require further anticoagulation. In conclusion, hirudin is an antithrombotic drug of high quality and may represent an attractive alternative to UFH and LMWHs in the management of VTE, and it is among the agents of choice in patients with contraindications to heparin therapy (such as HIT patients).

Topics: Animals; Hirudin Therapy; Hirudins; Humans; Therapeutic Equivalency; Thromboembolism; Venous Thrombosis

In the absence of prophylaxis, elective orthopedic surgery is associated with a high risk of venous thromboembolic events that are responsible for substantial morbidity and mortality. Despite the publication of articles questioning the significance of fatal pulmonary embolism (PE) following elective hip replacement, recent reports support the need for effective thromboprophylaxis in this indication. These reports also provide evidence of a significant reduction in fatal PE and overall mortality provided by treatment with low-molecular-weight heparin (LMWH), compared with unfractionated heparin. Even with the most effective prophylaxis currently available, however, deep vein thrombosis still develops in a minority of high-risk patients, indicating a need for improved therapies. Desirudin, a novel recombinant hirudin and direct thrombin inhibitor, has been shown to provide more effective prophylaxis than the most widely used LMWH, enoxaparin, in orthopedic surgery patients with multiple thromboembolic risk factors. This benefit was not associated with any increase in bleeding. Regional anesthesia and use of graduated compression stockings may provide additional independent reductions in thromboembolic risk in elective orthopedic surgery.

Topics: Anesthesia, Conduction; Anticoagulants; Bandages; Chondroitin Sulfates; Dermatan Sulfate; Drug Combinations; Heparin, Low-Molecular-Weight; Heparitin Sulfate; Hirudin Therapy; Hirudins; Humans; Logistic Models; Postoperative Complications; Pulmonary Embolism; Recombinant Proteins; Risk Factors; Venous Thrombosis

Joint replacement surgery is complicated by a high rate of postoperative venous thromboembolism (VTE). Current thromboprophylactic approaches reduce the rate of VTE, but the incidence remains as high as 20% to 50%. Recombinant hirudins, such as desirudin and lepirudin, function by directly inhibiting thrombin, and are a new development in antithrombotic therapy. In two multicenter studies, desirudin was found to be superior to unfractionated heparin (UFH) in the prevention of deep vein thrombosis (DVT) after total hip alloplasty. A further trial of more than 2,000 patients undergoing elective hip replacement compared the thromboprophylactic efficacy of desirudin versus the low-molecular-weight heparin (LMWH) enoxaparin. Desirudin was more effective than LMWH in providing effective prophylaxis, and maintained superiority in patients with additional risk. Desirudin was shown to be equally safe and did not require laboratory monitoring. Desirudin (15 mg twice daily) is an efficient therapy for DVT prevention in hip alloplasty patients at additional risk.

Topics: Arthroplasty, Replacement, Hip; Cost-Benefit Analysis; Drug Costs; Fibrinolytic Agents; Heparin, Low-Molecular-Weight; Hirudin Therapy; Hirudins; Humans; Recombinant Proteins; Venous Thrombosis

The past decade has seen many important advances in the pathogenesis, clinical and laboratory diagnosis, and management of heparin-induced thrombocytopenia (HIT), one of the most common immune-mediated adverse drug reactions. HIT is caused by IgG antibodies that recognize complexes of heparin and platelet factor 4, leading to platelet activation via platelet Fc gamma IIa receptors. Formation of procoagulant, platelet-derived microparticles, and, possibly, activation of endothelium generate thrombin in vivo. Thrombin generation helps to explain the strong association between HIT and thrombosis, including the newly recognized syndrome of warfarin-induced venous limb gangrene. This syndrome occurs when acquired protein C deficiency during warfarin treatment of HIT and deep venous thrombosis leads to the inability to regulate thrombin generation in the microvasculature. The central role of HIT antibodies in causing HIT, as well as refinements in laboratory assays to detect these antibodies, means that HIT should be considered a clinicopathologic syndrome. The diagnosis can be made confidently when one or more typical clinical events (most frequently, thrombocytopenia with or without thrombosis) occur in a patient with detectable HIT antibodies. The central role of thrombin generation in this syndrome provides a rationale for the use of anticoagulants that reduce thrombin generation (danaparoid) or inhibit thrombin (lepirudin).

Topics: Antibodies; Anticoagulants; Antithrombin III; Chondroitin Sulfates; Dermatan Sulfate; Drug Combinations; Fibrinolytic Agents; Gangrene; Heparin; Heparinoids; Heparitin Sulfate; Hirudin Therapy; Hirudins; Humans; Immunoglobulin G; Leg; Platelet Activation; Platelet Factor 4; Protein C Deficiency; Receptors, IgG; Recombinant Proteins; Retrospective Studies; Syndrome; Thrombin; Thrombocytopenia; Venous Thrombosis; Warfarin

Direct thrombin inhibitors offer potential advantages over unfractionated heparin but have been poorly studied in children.. To determine appropriate dosing of bivalirudin in children and adolescents and the relationship between activated partial thromboplastin time (APTT) and plasma bivalirudin concentration.. The UNBLOCK (UtilizatioN of BivaLirudin On Clots in Kids) study was an open-label, single-arm, dose-finding, pharmacokinetic, safety and efficacy study of bivalirudin for the acute treatment of deep vein thrombosis (DVT) in children aged 6 months to 18 years. Drug initiation consisted of a bolus dose (0.125 mg kg(-1) ) followed by continuous infusion (0.125 mg kg h(-1) ). Dose adjustments were based on the APTT, targeting a range of 1.5-2.5 times each patient's baseline APTT. Safety was assessed by specific bleeding endpoints and efficacy by repeat imaging at 48-72 h and 25-35 days.. Eighteen patients completed the study. Following the bolus dose and the initial infusion rate, most patients' APTT values were within the target range. The infusion rate bivalirudin correlated more closely with drug concentration than the APTT. At 48-72 h, nine (50%) patients had complete or partial thrombus resolution, increasing to 16 (89%) at 25-35 days. No major and one minor bleeding event occurred.. Bivalirudin demonstrated reassuring safety and noteworthy efficacy in terms of early clot resolution in children and adolescents with DVT. Although a widely available and familiar monitoring tool, the APTT correlates poorly with plasma bivalirudin concentration, possibly limiting its utility in managing pediatric patients receiving bivalirudin for DVT.

Topics: Adolescent; Age Factors; Antithrombins; Biomarkers; Child; Child, Preschool; Critical Illness; Dose-Response Relationship, Drug; Drug Monitoring; Female; Hemorrhage; Hirudins; Humans; Infant; Infusions, Intravenous; Injections, Intravenous; Male; Partial Thromboplastin Time; Peptide Fragments; Prospective Studies; Recombinant Proteins; Venous Thrombosis

This randomized, exploratory study compared the incidence of heparin-dependent antibodies associated with subcutaneous (SC) desirudin or heparin given for deep-vein thrombosis prophylaxis following cardiac and thoracic surgery.. Adult patients scheduled for elective cardiac or thoracic surgery received desirudin 15 mg SC twice daily or unfractionated heparin 5000 units SC thrice daily. Duration of thrombosis prophylaxis was determined by the treating physician. Primary outcome measure was the incidence of new antibody formation directed against platelet factor 4 (PF4)/heparin complex. Secondary outcomes included bleeding and thrombotic complications. Blood was tested for anti-PF4/heparin antibodies at baseline, after surgery prior to study drug administration, postdrug day (PDD) 2, PDD 7, and at 1 month. Doppler studies were done before discharge.. Of 120 patients, 61 received desirudin, 59 received heparin. New PF4/heparin antibodies occurred in 10.2% and 13.6% of desirudin- and heparin-treated patients, respectively. Among desirudin patients with no heparin exposure, none (0/36) developed PF4/heparin antibodies versus 17.1% with heparin exposure. Incidence of deep venous thrombosis was 4.9% and 3.4% in the desirudin and heparin groups, respectively. Two heparin-group patients developed pulmonary embolism. Two patients per group had bleeding events; no patients required re-exploration for bleeding complications. Median chest tube output was similar with desirudin (900 mL) and heparin (692 mL) as was blood transfusion requirements of more than 2 units (5/61, desirudin; 2/59 heparin).. The incidence of thrombotic events was low in both groups. There were no safety concerns, and desirudin was not associated with anti-PF4/heparin antibodies.

Topics: Antibodies; Anticoagulants; Cardiac Surgical Procedures; Female; Heparin; Hirudins; Humans; Male; Middle Aged; Partial Thromboplastin Time; Platelet Factor 4; Recombinant Proteins; Thoracic Surgical Procedures; Venous Thrombosis

Whether anticoagulant therapy should be used after spinal-cord injury (SCI) surgery was controversial. The anticoagulation characteristics of a newly developed anticoagulant, recombinant neorudin (EPR-hirudin (EH)), were explored using a rat model of SCI to provide a basis for clinical anticoagulation therapy of SCI.. A rat model of SCI was developed by Allen's method. Then, thrombosis in the inferior vena cava was induced by ligation. The low-bleeding characteristics of EH were explored by investigating dose-response and time-effect relationships, as well as multiple administration of EH, on thrombus formation complicated with SCI.. EH inhibited thrombosis in a dose-dependent manner by reducing the wet weight and dry weight of the thrombus. An inhibiting action of EH on thrombosis was most evident in the group given EH 2 h after SCI. After multiple intravenous doses of EH, thrombosis inhibition was improved to that observed with low molecular weight heparin (LMWH) (87% vs 90%). EH administration after SCI neither increased bleeding in the injured spine nor damaged to nerve function. Bleeding duration and activated partial thromboplastin time were increased in the high-dose EH group compared with that in the normal-saline group, but were lower than those in the LMWH group.. EH can reduce thrombus formation in a rat model of SCI, and bleeding is decreased significantly compared with that using LMWH. EH may prevent thrombosis after SCI or spinal surgery.

Topics: Administration, Intravenous; Animals; Anticoagulants; Heparin, Low-Molecular-Weight; Hirudins; Rats; Spinal Cord Injuries; Venous Thrombosis

Due to the high recurrence rate and mortality of venous thrombosis, there is an urgent need for research on antithrombotic strategies. Because of the short half-life, poor targeting capabilities, bleeding complications, and neurotoxic effects of conventional pharmacological thrombolysis methods, it is essential to develop an alternative strategy to noninvasive thrombolysis and decrease the recurrence rate of venous thrombosis. A platelet-mimetic porphyrin-based covalent organic framework-engineered melanin nanoplatform, to target delivery of hirudin to the vein thrombus site for noninvasive thrombolysis and effective anticoagulation, is first proposed. Owing to the thrombus-hosting properties of platelet membranes, the nanoplatform can target the thrombus site and then activate hyperthermia and reactive oxygen species for thrombolysis under near-infrared light irradiation. The photothermal therapy/photodynamic therapy combo can substantially improve the effectiveness (85.7%) of thrombolysis and prevent secondary embolism of larger fragments. Afterward, the highly loaded (97%) and slow-release hirudin (14 days) are effective in preventing the recurrence of blood clots without the danger of thrombocytopenia. The described biomimetic nanostructures offer a promising option for improving the efficacy of thrombolytic therapy and reducing the risk of bleeding complications in thrombus associated diseases.

Topics: Biomimetics; Hirudins; Humans; Thrombolytic Therapy; Thrombosis; Venous Thrombosis

Recombinant neorudin (EPR-hirudin, EH) is an inactive prodrug that is converted to its active metabolite, hirudin variant 2-Lys47 (HV2), at the thrombus site. We aimed to investigate the mechanism underlying site-selective bioconversion of EH to HV2 at the thrombus target site and metabolic transformation of EH in patients with deep vein thrombosis (DVT).. Metabolites in healthy volunteer plasma and urine after intravenous administration of EH were determined to elucidate how EH was metabolised after releasing HV2 at the target site in patients with DVT. After intravenous administration of EH in rats with venous thrombosis, the concentrations of EH in the blood and thrombus and the antithrombotic activity of EH were measured to predict whether EH could release HV2 at the thrombus site to exert anticoagulant effect in patients with DVT.. In healthy volunteers, EH and HV2 were predominantly excreted in the urine. Nine EH metabolites and ten HV2 metabolites truncated at the C-terminal were identified as N-terminal fragments, and these had the same cleavage sites. In rats with venous thrombosis, the area under the curve ratio of HV2 between the thrombus and blood was 29.5. The weight of wet thrombus was decreased with the production of HV2 by the cleavage of EH. The prothrombin time (PT) and prothrombin time (TT) changed proportionally to the concentration of EH and HV2 in the blood.. EH selectively accumulates and releases HV2 in the thrombus to exert antithrombotic effects, thus lowering the bleeding risk. Moreover, after conversion, EH may follow the same metabolic profile as that of HV2 in patients with DVT.

Topics: Animals; Anticoagulants; Hirudins; Humans; Rats; Recombinant Proteins; Thrombosis; Venous Thrombosis

Recombinant neorudin (EPR-hirudin, EH), a low-bleeding anticoagulant fusion protein, is an inactive prodrug designed to be converted to the active metabolite, hirudin variant 2-Lys47 (HV2), locally at the thrombus site by FXa and/or FXIa, following activation of the coagulation system. Our aim was to evaluate the prodrug characteristics of EH by comparing the biotransformation of EH and HV2 in biological matrices, including rat blood, liver, and kidney homogenates, demonstrating the cleavage of EH to HV2 by FXa and FXIa, and comparing the conversion of EH to HV2 between fresh whole blood and whole-blood clot homogenate, using ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS). Both EH and HV2 were stable in blood and unstable in the liver and kidney homogenates. Eight EH metabolites and eight HV2 metabolites identified as N-terminal fragments were found in the liver and kidney. C-terminal proteolysis is therefore the major metabolic pathway, with serine/cysteine carboxypeptidases and metallocarboxypeptidases being responsible for the degradation of EH and HV2 in the liver and kidney, respectively. EH was cleaved to release HV2 by FXIa. Higher levels of HV2 were produced from EH in the whole-blood clot homogenate, in which the coagulation system was activated compared with those in fresh whole blood. In conclusion, the metabolism of EH and HV2 shares the same cleavage pattern, and EH is transformed into HV2 when the coagulation system is activated, where FXIa is a specific enzyme. Our in vitro study revealed the anticipated prodrug characteristics of EH newly designed as an inactive prodrug of hirudin.

Topics: Animals; Anticoagulants; Biotransformation; Hirudins; Kidney; Liver; Male; Prodrugs; Rats, Wistar; Recombinant Fusion Proteins; Venous Thrombosis

Topics: Aged, 80 and over; Antibodies; Anticoagulants; Blood Platelets; Dalteparin; Female; Fondaparinux; Hip Fractures; Hirudins; Humans; Immunoglobulins, Intravenous; Immunologic Factors; Morpholines; Peptide Fragments; Platelet Count; Polysaccharides; Recombinant Proteins; Rivaroxaban; Thiophenes; Thrombocytopenia; Venous Thrombosis

The risk of thrombotic complications such as deep vein thrombosis (DVT) during tumor development is well known. Tumors release into the circulation procoagulant microparticles (MPs) that can participate in thrombus formation following vessel injury. The importance of this MP tissue factor (TF) in the initiation of cancer-associated DVT remains uncertain.. To investigate how pancreatic cancer MPs promote DVT in vivo.. We combined a DVT mouse model in which thrombosis is induced by flow restriction in the inferior vena cava with one of subcutaneous pancreatic cancer in C57BL/6J mice. We infused high-TF and low-TF tumor MPs to determine the importance of TF in experimental cancer-associated DVT.. Both tumor-bearing mice and mice infused with tumor MPs subjected to 3 h of partial flow restriction developed an occlusive thrombus; fewer than one-third of the control mice did. We observed that MPs adhered to neutrophil extracellular traps (NETs), which are functionally important players during DVT, whereas neither P-selectin nor glycoprotein Ib were required for MP recruitment in DVT. The thrombotic phenotype induced by MP infusion was suppressed by hirudin, suggesting the importance of thrombin generation. TF carried by tumor MPs was essential to promote DVT, as mice infused with low-TF tumor MPs had less thrombosis than mice infused with high-TF tumor MPs.. TF expressed on tumor MPs contributes to the increased incidence of cancer-associated venous thrombosis in mice in vivo. These MPs may adhere to NETs formed at the site of thrombosis.

Topics: Animals; Antithrombins; Carcinoma, Pancreatic Ductal; Cell Line, Tumor; Cell-Derived Microparticles; Disease Models, Animal; Extracellular Traps; Hirudins; Ligation; Male; Mice, Inbred C57BL; Mice, Knockout; P-Selectin; Pancreatic Neoplasms; Platelet Glycoprotein GPIb-IX Complex; Regional Blood Flow; Thromboplastin; Vena Cava, Inferior; Venous Thrombosis

Bivalirudin is an ultrashort acting direct thrombin inhibitor, which has been used in place of heparin in selected settings. We describe our preliminary experience with the use of bivalirudin in patients who required anticoagulation for a deep vein thrombosis, prosthetic heart valve, or hypercoagulable state but were felt to be at high risk for the use of heparin.. Eight patients in our neurocritical care unit required anticoagulation but were felt to be poor candidates for heparin either due to heparin-induced thrombocytopenia or due to high risk for intracranial hemorrhage. A standard protocol was utilized for bivalirudin with a loading dose of 0.75 mg/kg followed by a continuous infusion of 0.15 mg/kg hr. Serial aPTT levels were checked on a routine basis to monitor therapeutic effect. The bivalirudin infusion was continued for a period of 2 days to 2 weeks prior to starting coumadin therapy.. These patients were in the early postoperative period (within 48 h) following craniotomy, had suffered a recent large hemispheric infarct with hemorrhagic conversion, or had presented with an acute intracerebral hemorrhage. In this small series of patients, no intracranial hemorrhagic complications were encountered. No patients demonstrated progressive systemic thrombotic issues while on bivalirudin.. Based on these findings, bivalirudin may represent a reasonable alternative in patients for whom heparin anticoagulation is contraindicated. A larger multicenter trial of bivalirudin in this setting may be appropriate.

Topics: Adult; Aged; Aged, 80 and over; Antithrombins; Female; Heart Valve Prosthesis; Hirudins; Humans; Intracranial Hemorrhages; Male; Middle Aged; Peptide Fragments; Recombinant Proteins; Retrospective Studies; Thromboembolism; Thrombophilia; Treatment Outcome; Venous Thrombosis

The authors present the case of a nulliparous 34-year-old patient. At the tenth week of gestation, she developed phlebothrombosis of veins of the right leg and massive pulmonary embolism. After thrombolytic and heparin therapy she developed rethrombosis and heparin-induced thrombocytopenia type II. Lepirudin was introduced in therapy and in the 12th week of gestation acenocumarol was added. After the 34th week, she received danaparoid sodium. After a week, by cesarean section, a healthy and mature female was delivered.

Topics: Acenocoumarol; Adult; Anticoagulants; Cesarean Section; Chondroitin Sulfates; Dermatan Sulfate; Female; Fibrinolytic Agents; Gestational Age; Heparin; Heparitin Sulfate; Hirudins; Humans; Pregnancy; Pregnancy Complications; Pregnancy Outcome; Pulmonary Embolism; Recombinant Proteins; Thrombocytopenia; Venous Thrombosis

Patients with central nervous system (CNS) malignancies have a substantial risk for developing both thrombotic and bleeding disorders. The risk of venous thromboembolism (VTE) is substantially higher in these patients, both in the perioperative period and throughout their disease course. Patients with CNS malignancy harbor a latent hypercoagulability, which predisposes to VTE, as do postoperative immobility, hemiparesis, and other factors. The management of VTE in these patients is complex, given the significant morbidity and mortality associated with intratumoral hemorrhage. In the past, the perceived risk of intracranial hemorrhage limited the use of anticoagulation for the management of VTE with many favoring nonpharmacologic methods for prophylaxis and treatment. Inferior vena cava (IVC) filters have since lost favor at many centers given significant complications, which appear to be more frequent in patients with CNS malignancy. Recent studies have demonstrated safe and efficacious use of anticoagulation in these patients with a low incidence of intracranial hemorrhage. Treatment of established VTE is now recommended in this population with many centers favoring low-molecular-weight heparin (LMWH) versus oral warfarin for short- or long-term treatment. We advocate a multimodality approach utilizing compression stockings, intermittent compression devices, and heparin in the perioperative setting as the best proven method to reduce the risk of VTE. In the absence of a strict contraindication to systemic anticoagulation, such as previous intracranial hemorrhage or profound thrombocytopenia, we recommend LMWH in patients with newly diagnosed VTE and a CNS malignancy.

Topics: Antibodies, Monoclonal, Humanized; Anticoagulants; Arginine; Bevacizumab; Central Nervous System Neoplasms; Fondaparinux; Glioblastoma; Glioma; Hemorrhage; Heparin, Low-Molecular-Weight; Hirudins; Humans; Pipecolic Acids; Polysaccharides; Postoperative Complications; Pulmonary Embolism; Recombinant Proteins; Sulfonamides; Thrombocytopenia; Vena Cava Filters; Venous Thromboembolism; Venous Thrombosis; Warfarin

Thrombin inhibition is an important objective in the prevention and treatment of thrombosis. A new molecule, dabigatran etexilate or Pradaxa(®), has been recently licensed for thromboprophylaxis in major orthopedic surgery in several countries but not in the USA. In contrast, the FDA has approved it for prevention in patients with non-valvular atrial fibrillation. This new orally active anticoagulant is being developed for the treatment of venous thromboembolism and acute coronary syndromes in patients with non-valvular atrial fibrillation. Dabigatran is a reversible inhibitor of free thrombin and clot-bound thrombin. An oral thrombin inhibitor melagatran is no longer available due to hepatic toxicity. Several other thrombin inhibitors are used via parenteral administration: lepirudine and desirudine, bivalirudine and argatroban. They are mostly given to patients with heparin-induced thrombocytopenia (HIT). Bivalirudine is used for acute coronary syndrome in patients undergoing percutaneous interventions. The main pharmacologic characteristics of thrombin inhibitor agents are presented focusing on dabigatran etexilate and including the main results of clinical trials.

Topics: Anticoagulants; Antithrombins; Benzimidazoles; Contraindications; Dabigatran; Drug Interactions; Heparin; Hirudin Therapy; Hirudins; Humans; Orthopedic Procedures; Peptide Fragments; Postoperative Complications; Pyridines; Recombinant Proteins; Thrombocytopenia; Thrombosis; Venous Thrombosis

Topics: Acute Coronary Syndrome; Aged, 80 and over; Antithrombins; Combined Modality Therapy; Coronary Angiography; Coronary Artery Bypass; Echocardiography; Embolic Protection Devices; Graft Occlusion, Vascular; Hirudins; Humans; Male; Peptide Fragments; Recombinant Proteins; Saphenous Vein; Thrombectomy; Venous Thrombosis

A 22-year-old woman presented on the 10th post-partum day with deep vein thrombosis involving the right ilio-femoral and popliteal veins. This thrombosis was refractory to conventional anticoagulation and subsequently over a period of 6 weeks progressed to involve inferior vena cava and right ventricle. A diagnosis of Behçet's disease was made on the clinical grounds of fever, night sweats, and recurrent oral ulcers. In view of refractory thrombosis, anticoagulation with lepirudin was commenced followed by thrombolysis with streptokinase. After thrombolysis, anticoagulation was switched to fondaparinux. Intracardiac thrombus, oral ulcers, constitutional symptoms, and inflammatory indices resolved on 20 mg of oral prednisolone. This case highlights that management of thrombosis unresponsive to conventional anticoagulation requires careful consideration of the underlying conditions, the sites of thrombosis, as well as of the available treatment options. Intravenous lepirudin is a valuable therapeutic option when anticoagulation with warfarin or LMWH is not efficacious. Thrombolytic therapy may be used to treat intracardiac thrombi more rapidly, and possibly more efficiently, than surgery. The addition of corticosteroids or other immunosuppressive drugs is necessary in order to achieve a full resolution of thrombosis.

Topics: Anticoagulants; Behcet Syndrome; Female; Fibrinolytic Agents; Fondaparinux; Heart Ventricles; Hirudins; Humans; Iliac Vein; Polysaccharides; Popliteal Vein; Postpartum Period; Pregnancy; Pregnancy Complications, Hematologic; Recombinant Proteins; Streptokinase; Vena Cava, Inferior; Venous Thrombosis; Young Adult

Topics: Anticoagulants; Female; Fondaparinux; Hematocrit; Heparin; Hirudins; Humans; Middle Aged; Platelet Count; Polysaccharides; Recombinant Proteins; Thrombocytopenia; Ultrasonography; Venous Thrombosis

Topics: Animals; Antithrombins; Arthroplasty, Replacement, Hip; Drug Administration Schedule; Drug Costs; Fibrinolytic Agents; Hirudins; Humans; Injections, Subcutaneous; Recombinant Proteins; Treatment Outcome; Venous Thrombosis

Topics: Anticoagulants; Antithrombins; Arginine; Fibrinolytic Agents; Heparin; Hirudins; Humans; Pipecolic Acids; Platelet Aggregation Inhibitors; Recombinant Proteins; Sulfonamides; Thrombectomy; Thrombocytopenia; Time Factors; Venous Thrombosis

Thromboprophylaxis during pregnancy can be challenging when heparin is contraindicated. Limited data exist regarding alternative anticoagulants in the setting of pregnancy.. We present a patient with antiphospholipid syndrome who developed heparin-induced thrombosis in the third trimester of pregnancy. She was treated with therapeutic doses of intravenous lepirudin until delivery. Induction of labor, regional anesthesia, and forceps-assisted vaginal delivery were performed with no fetal, neonatal, or maternal complications. Postpartum, the patient was transitioned to warfarin therapy, and at 6 weeks postdelivery neither the patient nor her infant had developed any new problems.. Intravenous lepirudin use at therapeutic doses in late gestation as an alternative to heparin was accomplished with minimal maternal and fetal morbidity.

Topics: Anticoagulants; Female; Heparin; Hirudins; Humans; Infusions, Intravenous; Pregnancy; Pregnancy Complications, Cardiovascular; Pregnancy Trimester, Third; Recombinant Proteins; Venous Thrombosis

Topics: Acute Disease; Anticoagulants; Arginine; Blood Coagulation; Factor Xa Inhibitors; Fondaparinux; Hemorrhage; Heparin; Hirudins; Humans; International Normalized Ratio; Pipecolic Acids; Platelet Count; Polysaccharides; Recombinant Proteins; Research Design; Sulfonamides; Thrombin; Thrombocytopenia; Treatment Outcome; Venous Thrombosis; Warfarin

The purpose of this study was to design and evaluate hirudin (HIR) derivatives with low bleeding risk. In these derivatives, the factor (F) XIa, FXa, and thrombin recognition peptides (EPR, GVYAR, and LGPR, respectively) were linked to the N-terminus of HIR. The intact derivatives have no anticoagulant activity because of the extension of the N-terminus of HIR. After cleavage by the corresponding coagulation factor that occurs on the activation of the coagulation system and in the presence of the thrombus, its activity is released. This limited the anticoagulant activity of these derivatives to the vicinity of the thrombus, and as a result, systemic bleeding complications were avoided. The definite antithrombotic effect and low bleeding parameters of these derivatives were investigated in rat carotid artery and inferior vena cava thrombosis models. In both models, the three derivatives showed significant antithrombotic effects, indicating that anticoagulant activity could be successfully released in vivo. Moreover, the bleeding parameters of these derivatives were lower than that of HIR as indicated by the values of activated partial thromboplastin time (APTT) and thrombin time (TT). To further assess the safety of these derivatives, bleeding time was measured in a mouse tail-cut model. Although the derivatives had obvious effects on bleeding at a dose of 6 mg/kg, the effect of these derivatives on bleeding was significantly weaker than that of HIR at a dose of 1.5 mg/kg. Thus, the benefit-to-risk profiles of the derivatives were superior to that of HIR.

Topics: Animals; Anticoagulants; Bleeding Time; Blood Coagulation; Cloning, Molecular; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Fibrinolytic Agents; Hemorrhage; Hirudins; Male; Mice; Partial Thromboplastin Time; Prodrugs; Rats; Rats, Wistar; Recombinant Fusion Proteins; Risk Assessment; Thrombin Time; Thrombosis; Venous Thrombosis

Despite the fact that lytic therapy of thromboembolic disorder has been achieved, reocclusion of the damaged vessels and bleeding complication frequently reduce the therapeutic effect. In order to prevent the vessel reocclusion and enhance the therapeutic effect, combining the anticoagulant with the thrombolytic was assumed. Herein, we propose that restraining but locally releasing anticoagulant activity in the vicinity of thrombus is a way to alleviate the bleeding risk. A bifunctional fusion protein, termed as SFH (Staphylokinase (SAK) linked by FXa recognition peptide at N-terminus of Hirudin (HV)), was designed. SFH retained thrombolytic activity but no anticoagulant activity in thrombus-free blood due to the extension of the N-terminus of HV. However, it could locally liberate intact HV and exhibit anticoagulant activity when FXa or fresh thrombus was present. At equimolar dose, both improved antithrombotic and thrombolytic effects of SFH were observed in kappa-carrageenin inducing mouse-tail thrombosis model and rat inferior vena cava thrombosis model, respectively. Moreover, we observed significantly lower bleeding risk in mice and rats treated with SFH than with the mixture of SAK and HV with monitoring TT (P < 0.01), aPTT (P < 0.05) and PT (P < 0.05), and bleeding time (P < 0.05). In conclusion, SFH is a promising bifunctional therapeutic candidate with lower bleeding risk.

Topics: Animals; Anticoagulants; Blood Coagulation Tests; Disease Models, Animal; Fibrinolytic Agents; Hirudins; Male; Metalloendopeptidases; Mice; Rats; Recombinant Fusion Proteins; Recombinant Proteins; Thrombolytic Therapy; Venous Thrombosis

The recombinant protein SAK-RGD-K2-Hir is characterized by its fibrin-specific properties of plasminogen activation combined with antithrombin and antiplatelet activities. It was previously shown in our in-vitro studies to be a more potent and faster-acting thrombolytic agent compared with standard r-SAK. In order to document the effects of the thrombolytic potential of SAK-RGD-K2-Hir we examined this protein in an electrically induced carotid artery thrombosis model and stasis-induced venous model in rats. In the arterial thrombosis model, a bolus injection of SAK-RGD-K2-Hir was less effective than rt-PA and r-SAK. However, the most effective in the improvement and maintenance of carotid patency and in arterial thrombus mass reduction was SAK-RGD-K2. In contrast, all r-SAK derivatives reduced venous thrombus weight significantly in comparison to r-SAK and r-Hir. However, the most observable decrease in thrombus weight was obtained after application of recombinant proteins containing the r-Hir. The bleeding time was significantly prolonged in the animals treated with proteins containing r-Hir at a dose of 1.0 mg/kg. There were no observable changes in plasma fibrinogen concentration. In conclusion, our findings show thrombolytic activity in intravenous bolus injection of the novel thrombolytic agent SAK-RGD-K2-Hir in rats. Although this protein compares favourably with r-SAK in rat venous thrombolysis, we were unable to confirm the beneficial effects of SAK-RGD-K2-Hir over r-SAK and rt-PA in the carotid artery thrombolysis model. Furthermore, our results also suggest that SAK-RGD-K2-Hir bears a risk of bleeding, but this may be true for higher doses.

Topics: Animals; Bleeding Time; Blood Coagulation; Carotid Artery Thrombosis; Disease Models, Animal; Dose-Response Relationship, Drug; Electric Stimulation; Fibrin; Fibrinolytic Agents; Hemorrhage; Hirudins; Ligation; Male; Metalloendopeptidases; Partial Thromboplastin Time; Rats; Rats, Wistar; Recombinant Fusion Proteins; Thrombin Time; Time Factors; Tissue Plasminogen Activator; Vascular Patency; Venae Cavae; Venous Thrombosis

Topics: Adult; Female; Fibrinolytic Agents; Follow-Up Studies; Hirudins; Humans; Male; Mesenteric Veins; Middle Aged; Recombinant Proteins; Time Factors; Treatment Outcome; Venous Thrombosis

Type II heparin-induced thrombocytopenia (HIT) is a rare but well-recognised and potentially life-threatening complication of unfractionated heparin therapy, and has been reported in association with heparin locks for central venous lines. We report a case of type II HIT complicated by iliofemoral deep venous thrombosis and pulmonary embolism in a 43-year-old woman in the course of plasma exchange for myasthenia gravis. A Gamcath central venous line had been inserted femorally due to poor peripheral venous access, and this was locked with heparin 5000 U/ml between procedures. Twelve days after initial heparin exposure, she presented with new-onset thrombocytopenia, a painfully swollen right leg, and pleuritic pain. Deep venous thrombosis and pulmonary embolism were confirmed radiologically, and serology for heparin/PF4 antibodies was unequivocally positive. The line was removed, and she was successfully managed with intravenous lepirudin, switching to warfarin on platelet recovery. This case demonstrates that Type II HIT can occur in association with heparin line locks in the course of plasmapheresis, despite previous reports of successful use of plasma exchange to treat Type II HIT.

Topics: Adult; Catheterization, Central Venous; Female; Heparin; Hirudins; Humans; Myasthenia Gravis; Plasma Exchange; Pulmonary Embolism; Recombinant Proteins; Thrombocytopenia; Venous Thrombosis; Warfarin

To study the effect of recombinant hirudin (rH) on tPA-induced fibrinolysis and the possible mechanism of its action.. The effect of rH on thrombin-fibrin complex (Th-Fn) was detected by 99mTc labeled rH. In the in vitro clot lysis, tPA as plasminogen activator, and recalcified plasma as plasminogen resource were used to study the influence of rH on fibrinolysis by detecting TAFIa, D-Dimer and FXIII.. In a canine model of femoral artery thrombosis, a clear radioactivity strip was imaged in 30 - 60 min on a part image, and the femoral vein thrombosis developed at 30 min. rH efficiently inhibited clot regeneration. Addition of TM could inhibit clot lysis obviously, and CPI could shorten the delay of clot lysis which due to TAFIa. There was a dose-dependent relationship with TM concentration and TAFI activation. FXIII activation was inhibited by low concentration of rH ( < or = 0.2 u x mL(-1)), and the level of fibrinolysis product, D-Dimer, increased.. rH could inhibit the thrombin binding to fibrin. rH inhibited the activation of TAFI and FXIII by combining with thrombin which resulted in enhancement of thrombolysis.

Topics: Animals; Blood Coagulation; Carboxypeptidase B2; Carboxypeptidases; Dogs; Factor XIII; Femoral Artery; Femoral Vein; Fibrinolysis; Fibrinolytic Agents; Hirudins; Male; Plant Proteins; Protease Inhibitors; Recombinant Proteins; Thrombomodulin; Thrombosis; Venous Thrombosis

Delayed-onset heparin-induced thrombocytopenia is a syndrome in which thrombocytopenia and thrombosis begin several days after heparin discontinuation. Delayed-onset heparin-induced thrombocytopenia is caused by immunoglobulin G antibodies that are reactive against the heparin-platelet factor 4 complex in the absence of circulating heparin. We describe 2 patients with delayed-onset heparin-induced thrombocytopenia who presented to the emergency department. An 88-year-old man and a 62-year-old man experienced thrombocytopenia and thrombosis 9 or more days after heparin cessation and demonstrated a further decrease in platelet count on reexposure to heparin. Delayed-onset heparin-induced thrombocytopenia should be included in the differential diagnosis of a patient with recent heparin exposure who presents with thrombosis or thrombocytopenia.

Topics: Aged; Aged, 80 and over; Anticoagulants; Emergency Service, Hospital; Heparin; Hirudins; Humans; Male; Middle Aged; Platelet Factor 4; Recombinant Proteins; Thrombocytopenia; Time Factors; Venous Thrombosis

Topics: Adenocarcinoma; Adult; Anticoagulants; Arterial Occlusive Diseases; Autoimmune Diseases; Drug Resistance; Female; Heparin; Heparin, Low-Molecular-Weight; Hepatitis C, Chronic; Hirudins; Humans; Inflammatory Bowel Diseases; Male; Middle Aged; Neoplasms, Unknown Primary; Platelet Aggregation Inhibitors; Portal Vein; Pulmonary Embolism; Recombinant Proteins; Recurrence; Thrombocytopenia; Vena Cava, Inferior; Venous Thrombosis; Warfarin

This report describes a 72-year-old woman with atrial fibrillation who presented with lower extremity ischemia secondary to thromboembolism. After lower extremity thrombectomy, the patient developed heparin-induced thrombocytopenia with thrombosis (HITT). Her postoperative course was complicated by recurrent supraventricular and ventricular tachycardia, secondary to a mobile thrombus in the right atrium extending into the right ventricle. Because administration of heparin was contraindicated, the patient underwent off-pump right atrial thrombectomy during a brief period of inflow occlusion. Postoperatively, she was placed on lepirudin. Her platelet count normalized without any further thrombotic episodes, and she was discharged on warfarin.

Topics: Aged; Atrial Fibrillation; Cardiac Surgical Procedures; Cardiopulmonary Bypass; Combined Modality Therapy; Female; Follow-Up Studies; Heart Atria; Heparin; Hirudins; Humans; Lower Extremity; Postoperative Period; Recombinant Proteins; Risk Assessment; Thrombectomy; Thrombocytopenia; Thromboembolism; Treatment Outcome; Venous Thrombosis

The clinical utility of subcutaneous hirudins is discussed. The term "hirudins" refers to a class of antithrombotic agents structurally derived from the medicinal leech salivary protein hirudin. Breakthroughs in biotechnology over the past 20 years have resulted in the development of recombinant versions of hirudin (r-hirudin). Lepirudin is one such r-hirudin that is identical to natural hirudin except for the substitution of leucine for isoleucine at the N-terminus and the elimination of a sulfate group on the tyrosine at position 63. Another r-hirudin, desirudin, is identical to hirudin except for a valine-valine in the N-terminus and the absence of the sulfate group on tyrosine at position 63. Both r-hirudins are bivalent and tightly bind to both the catalytic site and the exposite of thrombin to exert their inhibitory effects on thrombin. Unfractionated heparin (UF) and low-molecular-weight heparins (LMWHs) are widely used in medical and surgical patients to prevent and treat arterial and venous thrombotic events. Besides bleeding, the major adverse effect of heparins is heparin-induced thrombocytopenia (HIT). HIT is associated with a paradoxical hypercoagulable state and marked risk of clinical thrombosis. Management of HIT requires the immediate cessation of all heparin exposure, and the initiation of an alternative anticoagulant. Because r-hirudins are effective agents and do not cross-react with HIT-associated antibodies, they are excellent anticoagulants in patients with past or current HIT. Clinical trials have also demonstrated the efficacy and safety of subcutaneous (s.c.) r-hirudins compared to heparins in non-HIT settings. Results of these trials support the use of r-hirudin therapy in patients with HIT or at risk of developing HIT. Additionally, case reports have described safe and effective use of s.c. r-hirudin therapy in the outpatient setting in both HIT and non-HIT patients.

Topics: Antithrombins; Clinical Trials as Topic; Heparin; Hirudins; Humans; Injections, Subcutaneous; Thrombocytopenia; United States; Venous Thrombosis

Outpatient treatment of deep venous thrombosis has gained widespread acceptance and is facilitated by the use of subcutaneous low molecular weight heparins (LMWH). We report two patients in whom subcutaneous lepirudin was used for long term anticoagulation after heart transplant or surgical pulmonary embolectomy because treatment with LMWH or warfarin was contraindicated, unsuccessful, or impractical. Neither bleeding complications nor recurrent thromboses developed. Subcutaneous lepirudin may be safely and effectively employed for the outpatient treatment of venous thrombosis in selected cases including patients with heparin-induced thrombocytopenia and in those who fail LMWH.

Topics: Adult; Ambulatory Care; Anticoagulants; Embolectomy; Heart Transplantation; Hirudins; Humans; Injections, Subcutaneous; Male; Postoperative Complications; Pulmonary Embolism; Recombinant Proteins; Thromboembolism; Treatment Outcome; Venous Thrombosis

The effect of new heparin mimetics (synthetic oligosaccharides) was studied in vitro with regard to thrombin generation (TG) in rat platelet rich plasma (PRP) and whole blood (WB) and in vivo on stasis-induced venous thrombosis in the rat. TG in PRP and in WB was highly dependent on platelet count and strongly influenced by the haematocrit. The peak of TG appeared to be significantly higher in WB than in PRP whereas the endogenous thrombin potential (ETP) was not significantly different under either condition. The effect of hirudin, the synthetic pentasaccharide SR90107/Org31540 (SP) and heparin were measured on TG in PRP and WB. We then compared the effect of two new synthetic heparin mimetics (SR121903A and SanOrg123781) with potent and comparable antithrombin (AT) mediated activity against factor Xa and thrombin. These two compounds were made of a pentasaccharide with a high affinity to AT, prolonged at the non-reducing end by an oligosaccharide chain recognised by thrombin. In SR121903A, the charge density and charge distribution was analogous to that of heparin whereas in SanOrg123781 the charges were only located on the last 5 saccharides of the non-reducing end of the molecule. In PRP and in WB, SR121903A acted on the lag time and on the AUC whereas SanOrg123781 inhibited thrombin formation with no effect on the lag time. SanOrg123781 was more potent in inhibiting TG than SR121903A. This difference was due to the structures of the compounds that differed in their ability to be neutralised by platelet factor 4. The antithrombotic effect of the two compounds was examined in a venous thrombosis model in rats. We observed that SanOrg123781 was more active than SR121903A and heparin. Taken together, these results indicate that the activity of oligosaccharides is greatly influenced by the global charge density of the molecule and show that SanOrg123781 is a potent and promising antithrombotic drug candidate.

Topics: Animals; Anticoagulants; Antithrombin III; Binding Sites; Blood; Blood Platelets; Carbohydrate Conformation; Carbohydrate Sequence; Drug Evaluation, Preclinical; Factor Xa Inhibitors; Fibrinolytic Agents; Hematocrit; Heparin; Hirudins; Male; Models, Animal; Molecular Sequence Data; Molecular Structure; Oligosaccharides; Plasma; Platelet Factor 4; Polysaccharides; Rats; Rats, Sprague-Dawley; Recombinant Proteins; Static Electricity; Structure-Activity Relationship; Thrombin; Thromboplastin; Venous Thrombosis

We report here a case of recurrent venous and arterial thromboembolism, Trousseau's syndrome, in a cancer patient who developed heparin-induced thrombocytopenia. She was treated with lepirudin and after establishing the patient-specific half-life for subcutaneous lepirudin, she was successfully maintained on this therapy for more than eight months. To our knowledge this case represents the longest reported use of subcutaneous lepirudin.

Topics: Anticoagulants; Arterial Occlusive Diseases; Female; Heparin; Hirudins; Humans; Injections, Subcutaneous; Kinetics; Middle Aged; Paraneoplastic Syndromes; Partial Thromboplastin Time; Recombinant Proteins; Recurrence; Thrombocytopenia; Thromboembolism; Venous Thrombosis

We report on a patient suffering from Budd-Chiari disease who developed heparin-induced thrombocytopenia preoperatively. Dorsocranial liver resection and hepatoatrial anastomosis were performed with the extracorporeal circulation and perioperative anticoagulation was achieved with r-hirudin. Surprisingly, thrombus formation was observed in the venous reservoir although intraoperative anticoagulation values were within the targeted level. An additional bolus of hirudin and rinsing the reservoir allowed unproblematic discontinuation of the cardiopulmonary bypass.

Topics: Adult; Budd-Chiari Syndrome; Dose-Response Relationship, Drug; Extracorporeal Circulation; Heart Atria; Heparin; Hepatic Veins; Hirudins; Humans; Infusions, Intravenous; Male; Partial Thromboplastin Time; Recurrence; Thrombocytopenia; Venous Thrombosis

Thromboembolic disease during pregnancy has traditionally been treated with heparin. If heparin cannot be used, then treatment options remain limited. Despite the recent availability of new anticoagulation agents, data relating to their use during pregnancy is lacking. Hirudin, a relatively new anti-thrombotic agent, through animal models has been shown to have a very low transplacental transfer, thus making it a candidate drug to be used during pregnancy in case of heparin allergy. This report describes a case of heparin allergy in a pregnant patient with recurrent DVT that was successfully managed with hirudin and coumadin.

Topics: Adult; Contraindications; Drug Hypersensitivity; Female; Heparin; Hirudins; Humans; Pregnancy; Pregnancy Complications, Hematologic; Venous Thrombosis; Warfarin

To report the case of a patient with HIT that received a prolonged infusion of r-hirudin (lepirudin; Refludan; Hoechst, France) before, during and after cardiopulmonary bypass (CPB) for aortic surgery. Although administration of r-hirudin for CPB anticoagulation has previously been reported, many questions persist concerning the best therapeutic regimen for CPB anticoagulation as well as the time of onset and the doses for postoperative anticoagulation.. A 65-yr-old man was admitted for surgery of aortic stenosis after an episode of acute pulmonary edema complicated by deep venous thrombosis in the context of documented HIT. The patient received r-hirudin for 13 dy before surgery at doses (0.4 mg x kg(-1) bolus followed by 0.15 mg x kg(-1) x hr(-1) continuous infusion) that maintained activated partial thromboplastin time (aPTT) ratios between 2 and 2.5. Anticoagulation for CPB was performed with r-hirudin given as 0.1 mg x kg(-1) i.v. bolus and 0.2 mg kg(-1) in the CPB priming volume. Anticoagulation during CPB was monitored with the whole blood activated coagulation time and ecarin clotting time (ECT) performed in the operating room with values corresponding to r-hirudin concentrations >5 microg x ml(-1) during CPB. Anticoagulation during CPB was uneventful. Two bleeding episodes, related to the r-hirudin regimen and necessitating allogeneic blood transfusion, occurred after surgery.. This case report confirms previous experience of the use of r-hirudin for anticoagulation during CPB and provides additional information in the context of prolonged r-hirudin infusion before and after CPB.

Topics: Aged; Anticoagulants; Aortic Valve; Aortic Valve Stenosis; Blood Coagulation; Blood Transfusion; Cardiopulmonary Bypass; Endopeptidases; Fibrinolytic Agents; Follow-Up Studies; Heart Valve Prosthesis Implantation; Heparin; Hirudin Therapy; Hirudins; Humans; Infusions, Intravenous; Injections, Intravenous; Male; Postoperative Hemorrhage; Recombinant Proteins; Thrombocytopenia; Venous Thrombosis; Whole Blood Coagulation Time

We report on a breastfeeding woman with deep venous thrombosis treated with hirudin because of heparin-induced thrombocytopenia, in whom hirudin was not detectable in human breastmilk.

Topics: Adult; Antithrombins; Breast Feeding; Female; Hirudin Therapy; Hirudins; Humans; Infant; Milk, Human; Venous Thrombosis

Heparin-induced thrombocytopenia (HIT) is the most common drug-related thrombocytopenia. Thromboembolic complications occur in approximately 50% of patients with HIT and result in limb amputation and death in up to 20% and 30% respectively. Because patients with a history of HIT may require future intravenous anticoagulation but have a high-risk of thromboembolism if re-challenged with heparin, alternative therapies are necessary when further anticoagulation is indicated. The use of direct thrombin inhibitors in HIT patients who also require thrombolytic therapy offers unique challenges to anticoagulant monitoring and safety. We present a case of progressive ileofemoral deep venous thrombosis in a patient with a history of HIT in order to review the combined use of hirudin and thrombolysis in this setting.

Topics: Anticoagulants; Heparin; Hirudin Therapy; Hirudins; Humans; Male; Middle Aged; Phlebography; Recombinant Proteins; Thrombocytopenia; Thrombolytic Therapy; Treatment Outcome; Venous Thrombosis

The novel recombinant hirudin analog CX-397 was investigated with respect to its pharmacological activity and antithrombin profiles in vivo and in vitro. In three different types of thrombosis models in rats, including stasis and thrombin-induced venous, glass surface-activated arterio-venous shunt, and ferric chloride-induced arterial thrombosis models, CX-397 and rHV-1 elicited potent antithrombotic effects, where the minimum effective doses of rHV-1 tended to be higher than those of CX-397 in the arterio-venous shunt and arterial thrombosis models. The hemorrhagic risk of CX-397 in template bleeding in rats was not higher than that of rHV-1, indicating that CX-397 is superior to rHV-1 for treating the platelet-dominant type of thrombosis. However, no differences were detected between CX-397 and rHV-1 in their effects on in vitro coagulation times and thrombin-induced platelet aggregation, suggesting the possibility that some unknown mechanisms other than simple thrombin inhibition are also involved in their antithrombotic actions.

Topics: Amino Acid Sequence; Animals; Arginine; Arterial Occlusive Diseases; Arteriovenous Shunt, Surgical; Chlorides; Drug Evaluation, Preclinical; Ferric Compounds; Fibrinolytic Agents; Glass; Hemorrhage; Heparin; Hirudin Therapy; Hirudins; Molecular Sequence Data; Pipecolic Acids; Platelet Aggregation; Platelet Aggregation Inhibitors; Rats; Recombinant Proteins; Sequence Alignment; Sequence Homology, Amino Acid; Serine Proteinase Inhibitors; Sulfonamides; Thrombin; Thrombosis; Vena Cava, Inferior; Venous Thrombosis

Topics: Fibrinolytic Agents; Hematoma; Hemorrhage; Hirudin Therapy; Hirudins; Humans; Pulmonary Embolism; Recombinant Proteins; Venous Thrombosis

Topics: Animals; Anticoagulants; Blood Coagulation Tests; Blood Pressure; Epoprostenol; Hirudins; Humans; In Vitro Techniques; Kallikreins; Rats; Venous Thrombosis

Topics: Acenocoumarol; Anticoagulants; Budd-Chiari Syndrome; Endotoxins; Escherichia coli Infections; Heparin; Hirudins; Hyperlipidemias; Pharmacology; Prothrombin Time; Rats; Research; Salmonella Infections; Salmonella Infections, Animal; Thrombophlebitis; Toxicology; Venous Thrombosis