Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.6 (thromboplastin)
13,278 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Antiphospholipid syndrome (APS) is an uncommon prothrombotic disorder that has been increasingly recognized in recent years. The diagnosis of APS must be associated with venous or arterial thrombosis or both. Patients with APS usually present with recurrent deep vein thrombosis, pulmonary thromboembolism, thromboembolic stroke, or myocardial infarction. Here, we report a case of a 61-year-old female who presented with a 3-month history of increasingly frequent retrosternal chest tightness. After treadmill test and thallium-201 myocardial perfusion scan, she was admitted and underwent elective coronary angiography but developed acute thrombosis after direct intracoronary stenting. She was successfully rescued with repeat percutaneous transluminal coronary angioplasty and prolonged heparin and glycoprotein IIb/IIIa antagonist use. Laboratory data showed prolongation of partial thromboplastin time and positive anti-cardiolipin antibody. These findings satisfied the criteria for APS; the patient was diagnosed with primary APS because she had neither typical symptoms nor signs of systemic lupus erythematosus or other immunologic disorders. Thereafter, long-term oral anticoagulant appeared to be effective. To our knowledge, this is the first report of acute stent thrombosis in a patient with primary APS.
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PMID:Acute thrombosis after elective direct intracoronary stenting in primary antiphospholipid syndrome: a case report. 1279 47

Despite major improvements in tools and significant refinements of techniques, microsurgical anastomosis still carries a significant risk of failure due to microvascular thrombosis. The key to improving the success of microvascular surgery may lie in the pharmacologic control of thrombus formation. Central to pathologic arterial thrombosis are platelets. Glycoprotein IIb/IIIa is a highly abundant platelet surface receptor that plays a major role in platelet aggregation by binding platelets to each other through the coagulation factor fibrinogen. To explore the ability of antithrombotic agents to prevent microvascular thrombosis, a rabbit ear artery model was used in which a standardized arterial injury results in predictable thrombus formation. This model was used to examine whether SR121566A, a specific and potent glycoprotein IIb/IIIa inhibitor, can successfully prevent microsurgical thrombosis. Using a coded, double-blind experimental design, 20 rabbits (40 arteries) were assigned to four treatment groups: (1) saline injection (n = 10), (2) acetylsalicylic acid 10 mg/kg (n = 10), (3) heparin 0.5 mg/kg bolus with subsequent intermittent boluses of 0.25 mg/kg every 30 minutes (n = 10), and (4) SR121566A 2 mg/kg bolus (n = 10). After vessel damage and clamp release, arteries were assessed for patency at 5, 30, and 120 minutes by the Acland refill test. Coagulation assays, in vivo bleeding times, and ex vivo platelet aggregation studies were also conducted. Scanning electron microscopy was used to examine mural thrombus composition.A significant, fourfold increase in vessel patency following administration of SR121566A over saline control (80 percent versus 20 percent patency, respectively, at 35 minutes after reperfusion, p < 0.01) was noted. This was correlated with marked inhibition of ex vivo platelet aggregation. This antiplatelet treatment did not prolong coagulation assays (mean international normalized ratio: saline, 0.66 +/- 0.04; SR121566A, 0.64 +/- 0.03; mean thromboplastin time: saline, 19.63 +/- 0.67; SR121566A, 17.87 +/- 3.27) and bleeding times (mean bleeding time: saline, 42 +/- 4; SR121566A, 48 +/- 6). Scanning electron microscopy demonstrated extensive platelet and fibrin deposition in control vessel thrombi. In contrast, thrombi from SR121566A-treated vessels demonstrated predominance of fibrin with few platelets when examined under scanning electron microscopy.Administration of SR121566A was associated with a significant increase in vessel patency, without deleterious effects on coagulation assays or bleeding times. The increase in vessel patency was correlated with inhibition of platelet aggregation and decreased platelet deposition, as demonstrated by scanning electron microscopy. Glycoprotein IIb/IIIa antagonists represent a new class of anti-platelet agents that may be suited for inhibiting microsurgical thrombosis. This study supports further investigation into the use of these agents in microsurgery.
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PMID:Inhibition of microsurgical thrombosis by the platelet glycoprotein IIb/IIIa antagonist SR121566A. 1283 91

An 18-month-old Oldenbourg filly was presented with a bleeding diathesis. Laboratory testing included platelet count, gingival bleeding time, prothrombin time (PT), activated partial thromboplastin time (aPTT), von Willebrand factor (vWf) antigen, clottable fibrinogen, clot retraction time, PFA-100 closure time, platelet aggregometry (on platelet-rich plasma), and thrombelastography (TEG). TEG was performed by using kaolin and tissue factor as coagulation activators. Expression of the platelet receptor for fibrinogen was assessed by flow cytometry by using anti CD41 (alpha(IIb) or glycoprotein IIb)/CD61 (beta(III) or glycoprotein IIIa) and anti-CD41 antibodies. Abnormal laboratory findings included prolonged oral mucosal bleeding time (>12 hours), prolonged closure time with collagen/ADP (>300 seconds), and absence of clot retraction after 60 minutes. TEG reaction times were similar with kaolin and tissue factor in the patient and a control horse. However, maximum amplitudes in the patient were decreased with both kaolin (43.7 mm; control, 63.9 mm) and tissue factor (37.7 mm; control, 57.8 mm). Platelet aggregation responses to ADP and collagen were profoundly reduced in the affected horse compared with a control. Flow cytometry showed an absence of CD41 and decreased expression of CD41/CD61-reacting antigen on the patient's platelets compared with those from a control horse. The laboratory findings supported a diagnosis of Glanzmann thrombasthenia, likely caused by a mutation in the gene encoding the GPIIb subunit.
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PMID:Glanzmann thrombasthenia in an Oldenbourg filly. 1752 98

The acute coronary syndrome (ACS) is one of the most frequent diagnoses in cardiology. The therapeutic corner-stones of ACS are PCI (percutaneous coronary intervention) and inhibition of blood coagulation. Current antiplatelet therapy consists of aspirin in combination with clopidogrel and glycoprotein IIb/IIIa blockade if needed. Prasugel is a new antiplatelet agent that is in the process of being approved for routine clinical use. In terms of antithrombotic therapy latest developments focus on drugs with anti-factor Xa activity, such as fondaparinux, or direct anti-thrombin activity, such as bivalirudin. This review discusses latest developments in the field of anti-platelet and anti-thrombotic therapy for ACS.
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PMID:[Anticoagulation in acute coronary syndrome. An update]. 1827 64

The conventional management of thrombotic disorders is based on the use of heparin, oral anticoagulants, and aspirin. The development of low molecular weight heparins and the synthesis of heparinomimetics such as the chemically synthesized pentasaccharide represent a refined use of heparin. Aspirin still remains the lead drug in the management of thrombotic and cardiovascular disorders. The newer antiplatelet drugs such as the adenosine diphosphate receptor inhibitors, glycoprotein IIb/IIIa (GPIIb/IIIa) inhibitors and other specific inhibitors have limited effects and have been tested in patients who have already been treated with aspirin. The oral anticoagulants such as warfarin provide a convenient and affordable approach in the long-term outpatient management of thrombotic disorders. The optimized use of these drugs still remains the approach of choice to manage thrombotic disorders. The new anticoagulant drugs target specific sites in the hemostatic network. There is a major thrust on the development of orally bioavailable anticoagulant drugs to replace oral anticoagulants. Heparin and low molecular weight heparins have been considered with various chemical enhancers for absorption. Both the factor Xa and antithrombin agents have been developed for oral use and some of these agents are in clinical development. Besides the limited bioavailability, the therapeutic indices of some of these drugs have been rather disappointing. Factor Xa inhibitors such as the pentasaccharides have undergone aggressive clinical development. The newer antiplatelet drugs have added a new dimension in the management of thrombotic disorders. The newer drugs are attractive for several reasons; however, none of these are expected to completely replace the conventional drugs in polytherapeutic approaches. It is conceivable that some of the newer drugs in combined modalities may mimic the broad therapeutic spectrum of heparins and warfarin. However, clinical validation is required for the therapeutic interchange for specific indications.
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PMID:The future of anticoagulation. 1830 91

The conventional management of thrombotic and cardiovascular disorders is based on the use of heparin, oral anticoagulants, and aspirin. Despite remarkable progress in life sciences, these drugs still remain a challenge and a mystery to us, and their use is far from optimized. The development of low-molecular-weight heparins and the synthesis of heparinomimetics, such as the chemically synthesized pentasaccharide, represent a refined use of heparin. Additional drugs from this knowledge will continue to develop; however, none of these drugs will ever match the polypharmacology of heparin. Aspirin still remains the leading drug in the management of thrombotic and cardiovascular disorders. The newer antiplatelet drugs such as adenosine diphosphate receptor inhibitors, glycoprotein IIb/IIIa inhibitors, and other specific inhibitors have limited effects and have been tested in patients who have already been treated with aspirin. Warfarin provides a convenient and affordable approach in the long-term outpatient management of thrombotic disorders. The optimized use of these drugs still remains as the approach of choice to manage thrombotic disorders. The new anticoagulant targets, including specific sites in the hemostatic network such as tissue factor, individual clotting factors (IIa, VIIa, IXa, Xa, XIIa, and XIIIa), recombinant forms of serpins (antithrombin, heparin cofactor II, and tissue factor pathway inhibitors), recombinant activated protein C, thrombomodulin, and site-specific serine protease inhibitor complexes have also been developed. There is a major thrust on the development of orally bioavailable anticoagulant drugs (anti-Xa and anti-IIa agents), which are slated to replace oral anticoagulants. Both the anti-factor Xa and antithrombin agents have been developed for oral use and have provided impressive clinical outcomes in sponsor trials for the postsurgical prophylaxis of venous thrombosis; however, safety concerns related to liver enzyme elevations and thrombosis rebound have been reported with their use. For these reasons, the U.S. Food and Drug Administration did not approve the orally active antithrombin agent ximelagatran for several indications. The synthetic pentasaccharide (fondaparinux) has undergone an aggressive clinical development. Unexpectedly, fondaparinux also produced major bleeding problems at minimal dosages. Fondaparinux represents only one of the multiple pharmacologic effects of heparins. Thus, its therapeutic index will be proportionately narrower. The newer antiplatelet drugs have added a new dimension in the management of thrombotic disorders. The favorable clinical outcomes with aspirin and clopidogrel have validated cyclooxygenase (COX)-1 and P2Y (12) receptors as targets for new drug development. Prasugrel, a novel thienopyridine, cangrelor, and AZD 6140 represent newer P2Y (12) antagonists. Cangrelor and AZD 6140 are direct inhibitors, whereas prasugrel requires metabolic activation. Though clinically effective, recent results have prompted a closure of a large clinical trial with prasugrel due to bleeding. The newer anticoagulant and antiplatelet drugs are attractive for several reasons; however, none of these are expected to replace the conventional drugs in polytherapeutic approaches. Heparins, warfarin, and aspirin will continue to play a major role in the management of thrombotic and cardiovascular disorders beyond 2010.
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PMID:Survival of heparins, oral anticoagulants, and aspirin after the year 2010. 1839 43

Argatroban is a hepatically metabolized, direct thrombin inhibitor used for prophylaxis or treatment of thrombosis in heparin-induced thrombocytopenia (HIT) and for patients with or at risk of HIT undergoing percutaneous coronary intervention (PCI). The objective of this review is to summarize practical considerations of argatroban therapy in HIT. The US FDA-recommended argatroban dose in HIT is 2 microg/kg/min (reduced in patients with hepatic impairment and in paediatric patients), adjusted to achieve activated partial thromboplastin times (aPTTs) 1.5-3 times baseline (not >100 seconds). Contemporary experiences indicate that reduced doses are also needed in patients with conditions associated with hepatic hypoperfusion, e.g. heart failure, yet are unnecessary for renal dysfunction, adult age, sex, race/ethnicity or obesity. Argatroban 0.5-1.2 microg/kg/min typically supports therapeutic aPTTs. The FDA-recommended dose during PCI is 25 microg/kg/min (350 microg/kg initial bolus), adjusted to achieve activated clotting times (ACTs) of 300-450 sec. For PCI, argatroban has not been investigated in hepatically impaired patients; dose adjustment is unnecessary for adult age, sex, race/ethnicity or obesity, and lesser doses may be adequate with concurrent glycoprotein IIb/IIIa inhibition. Argatroban prolongs the International Normalized Ratio, and published approaches for monitoring the argatroban-to-warfarin transition should be followed. Major bleeding with argatroban is 0-10% in the non-interventional setting and 0-5.8% periprocedurally. Argatroban has no specific antidote, and if excessive anticoagulation occurs, argatroban infusion should be stopped or reduced. Improved familiarity of healthcare professionals with argatroban therapy in HIT, including in special populations and during PCI, may facilitate reduction of harm associated with HIT (e.g. fewer thromboses) or its treatment (e.g. fewer argatroban medication errors).
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PMID:Reducing harm associated with anticoagulation: practical considerations of argatroban therapy in heparin-induced thrombocytopenia. 1933 78

Inhibition of coagulation is a key therapeutic principle in acute coronary syndromes (ACS). A plethora of substances is used in daily clinical practice to prevent thrombocyte aggregation, i.e. primary haemostasis, as well as activation of the coagulation cascade. Prevention of thrombocyte aggregation is accomplished by inhibiting thromboxane synthesis by acetyl salicylic acid, blockade of the ADP receptor, and by inhibition of the glycoprotein IIb/IIIa-receptor. Inhibition of the plasmatic coagulation in the setting of acute coronary syndromes is primarily achieved by the use of unfractionated or low-molecular weight heparins. Beyond this, several next-generation substances such as the novel, potent ADP receptor antagonist prasurgel or the selective direct thrombin- and factor Xa-antagonists are being developed and are investigated in clinical trials. It remains to be determined which place these novel substances will take in the armentarium of anticoagulants in acute coronary syndromes, and whether they will be employed in the majority of ACS-patients or just in certain sub-populations (e.g., in patients with a high or a low bleeding risk, in the presence of aspirin- or clopidogrel resistance etc.). The current review summarizes the mode of action as well as the clinical use of currently employed anticoagulants in acute coronary syndromes.
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PMID:[Antithrombotic therapy in acute coronary syndromes]. 1935 40

AZD0837 is in development as a new oral anticoagulant for use in thromboembolic disorders. In vivo, AZD0837 is converted to AR-H067637, a selective and reversible direct thrombin inhibitor. Established biochemical methods were used to assess and measure the biochemical and pharmacological properties of AR-H067637. Both direct Biacore binding studies of AR-H067637 with immobilised alpha-thrombin and inhibition studies using pre-steady state kinetics with thrombin in the fluid phase confirmed that AR-H067637 is a rapid-binding, reversible and potent (inhibition constant K(i) = 2-4 nM), competitive inhibitor of thrombin, as well as of thrombin bound to fibrin (clot-bound thrombin) or to thrombomodulin. The total amount of free thrombin generated in platelet-poor clotting plasma was inhibited concentration-dependently by AR-H067637, with a concentration giving half maximal inhibition (IC(50)) of 0.6 microM. Moreover, AR-H067637 is, with the exception of trypsin, a selective inhibitor for thrombin without inhibiting other serine proteases involved in haemostasis. Furthermore, no anticoagulant effect of the prodrug was found. AR-H067637 prolonged the clotting time concentration-dependently in a range of plasma coagulation assays including activated partial thromboplastin time, prothrombin time, prothrombinase-induced clotting time, thrombin time and ecarin clotting time. The two latter assays were found to be most sensitive for assessing the anticoagulant effect of AR-H067637 (plasma IC(50) 93 and 220 nM, respectively). AR-H067637 also inhibited thrombin-induced platelet activation (by glycoprotein IIb/IIIa exposure, IC(50) 8.4 nM) and aggregation (IC(50) 0.9 nM). In conclusion, AR-H067637 is a selective, reversible, competitive inhibitor of alpha-thrombin, with a predictable anticoagulant effect demonstrated in plasma coagulation assays.
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PMID:Biochemical and pharmacological effects of the direct thrombin inhibitor AR-H067637. 1949 47

To investigate the relationship between anticoagulation treatment and drug resistance in chest pain, levels of factor Xa residual activity were determined in patients seen in intensive care with recurrent chest pain and compared with levels in patients who had no ischaemic events during hospitalization. A total of 122 patients aged 18 - 75 years who were admitted to hospital with acute coronary syndrome and treated with enoxaparin were included. Of these, 62 patients had recurrent chest pain while hospitalized (group A) and 60 patients had an uneventful follow-up period (group B). Patients requiring primary percutaneous transluminal coronary angioplasty and/or treatment with glycoprotein IIb/IIIa inhibitors, and those with renal failure, a high risk of bleeding or receiving anti-inflammatory drugs were excluded from the study. Median levels (+/- interquartile range) of factor Xa residual activity were significantly higher in group A compared with group B (0.68 +/- 0.29 IU/ml versus 0.34 +/- 0.33 IU/ml). It is concluded that enoxaparin resistance, resulting in high levels of factor Xa residual activity, should be considered in patients with recurrent ischaemia.
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PMID:Role of enoxaparin resistance in recurrent chest pain in the intensive care unit. 1993 Aug 48


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