Antithrombotic efficacy of the vitamin K antagonist fluindione in a human Ex vivo model of arterial thrombosis : effect of anticoagulation level and combination therapy with aspirin.
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Thrombin is a main mediator of arterial thrombus formation, and its inhibition is an important antithrombotic strategy. However, the place of vitamin K antagonists among the different therapeutic strategies for preventing arterial thrombus formation is still debated. We studied the antithrombotic efficacy of the vitamin K antagonist fluindione in a human ex vivo model of arterial thrombosis and determined whether aspirin enhances fluindione efficacy. Ten healthy male volunteers were randomly assigned to receive fluindione, alone or in combination with aspirin (325 mg/d). Fluindione was given at increasing doses to give a stable international normalized ratio (INR) between 1.5 and 2.0 and between 2.1 and 3.0. We induced arterial thrombus formation ex vivo by exposing collagen- or tissue factor (TF)-coated coverslips in a parallel-plate perfusion chamber to native blood for 3 minutes at an arterial wall shear rate of 2600 s(-1). Platelet and fibrin deposition were measured by immunoenzymatic methods. Fluindione inhibited thrombus formation on TF-coated coverslips in a dose-dependent manner by 50% and 80% at INR 1.5 to 2.0 and INR 2.1 to 3.0, respectively (P<0.05). Fluindione in combination with aspirin inhibited TF-induced thrombus formation in a comparable manner. Collagen-induced thrombus formation was not reduced in subjects treated by fluindione. It was reduced by 50% to 60% in those treated with fluindione plus aspirin, regardless of the level of anticoagulation (P<0.05). Thus, the effectiveness of fluindione for preventing arterial thrombosis is dependent on the nature of the thrombogenic trigger. Fluindione is very effective in preventing TF- but not collagen-triggered thrombus formation. Aspirin enhances the antithrombotic effectiveness of fluindione, because combined treatment interrupts both TF- and collagen-induced thrombus formation. (+info)
The efficacy of long-term oral anticoagulant therapy and its laboratory assessment.
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The activated partial thromboplastin time is compared with the corresponding prothrombin ratio in 6378 samples of platelet-poor plasma from 446 patients treated for a total of more than 4500 patient/months with oral anticoagulatnts. A relative decrease in the activated partial thromboplastin time following deep vein thrombosis is described, which tends to become less obvious during the first year of treatment and is greater in older patients. Although this relative decrease is also found in patients treated after cerebrovascular accidents, it is not found in patients treated after myocardial infarction or in patients with mitral valve disease treated prophylactically with long-term oral anticoagulants. It is though possible that these changes following deep vein thrombosis might be useful in helping to determine the duration of oral anticoagulant treatment. (+info)
Trial of long-term anticoagulant therapy in the treatment of small stroke associated with a normal carotid arteriogram.
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The clinical features of 49 patients who had sustained small strokes in the internal carotid artery territory, who were normotensive, free from cardiac or other relevant disease, and who each had a normal appropriate single vessel angiogram are presented. These were randomized into two groups: group A, 25 patients, who received only supportive treatment; group B, 24 patients who were treated with anticoagulants for an average period of 18 months. There was a reduced incidence of neurological episodes during the administration of anticoagulant therapy but, after treatment was discontinued, there was no significant difference between the two groups. In view of the relatively benign prognosis for this syndrome, unless special facilities exist for the personal control of anticoagulant treatment, the dangers may outweigh the benefits. (+info)
INITIAL EXPERIENCE WITH THROMBOTEST.
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The initial experience of using Thrombotest instead of Quick's one-stage prothrombin time to control anticoagulant therapy is described.Patients well controlled by the Quick test are often found to be over-anticoagulated by Thrombotest standards, so the introduction of Thrombotest has led to widespread reductions in dosage. No improvement in stability of control has been noted. The main advantages of Thrombotest seem to be its technical simplicity and the comparability of results obtained in different laboratories. (+info)
AN INVESTIGATION OF THE HEMORRHAGIC DIATHESIS IN PATIENTS RECEIVING COUMARIN AND INDANEDIONE ANTICOAGULANTS.
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Coagulation studies were carried out on 10 patients who bled during anticoagulant therapy, in whom no other underlying cause for bleeding could be demonstrated, and 10 patients with similar degrees of hypoprothrombinemia who were not bleeding. The average age and sex distribution of the two groups was similar, and no association was noted between the occurrence of hemorrhage and the type of anticoagulant used, the duration of treatment or the nature of the underlying disease. Comparison of the results revealed no differences in the levels of factors II, VII, IX and X or in the glass and silicone (Siliclad) clotting time, the thromboplastin generation test and Thrombotest. It was concluded that all patients on anticoagulant drugs whose prothrombin time is in the therapeutic range or longer are potential bleeders and that one cannot necessarily predict those who will bleed on the basis of coagulation studies. (+info)
Confirmation of indandione rodenticide toxicoses by mass spectrometry/mass spectrometry.
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Mass spectrometry/mass spectrometry (MS/MS) with collision-activated dissociation (CAD) was utilized to unequivocally distinguish 1,3-indandione rodenticides in 2 cases of anticoagulant toxicosis. Anecdotal evidence provided by the veterinarian in a case involving feedlot cows and physical evidence at the site of occurrence in a similar case involving lambs strongly implicated diphenadione (diphacinone; DP) in both instances. However, high performance liquid chromatography indicated chlorophacinone (CP), not DP, was present in the blood samples obtained from both cows and lambs. Intact 1,3-indandiones exhibit poor gas chromatographic properties, so procedures were developed for analysis by MS/MS using a direct exposure probe for sample introduction. The EI mass spectra of DP and CP contained a base peak at m/z 173, with molecular ions (M+) at m/z 340 and m/z 374 (Cl isotope cluster), respectively. Corresponding MS/MS CAD parent ion spectra of m/z 173 showed an ion of m/z 340 for DP and 374 (Cl cluster) for CP. CAD analysis of the blood extracts showed a parent ion scan of m/z 173 identical to that of CP, with the m/z 374 (Cl cluster). (Additional evidence was obtained by MS/MS examination of the CAD daughter ion spectrum of m/z 374.) Blood extracts from the affected animals revealed CAD daughter ion spectra for m/z 374 identical to that of reference CP. Positive confirmation of CP in both cases led to identification of the source of the toxicant and prevention of further animal exposures. (+info)
Personalized versus non-personalized computerized decision support system to increase therapeutic quality control of oral anticoagulant therapy: an alternating time series analysis.
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BACKGROUND: The quality control of oral anticoagulant therapy (OAT) during the initiation and maintenance treatment is generally poor. Physicians' ordering of OAT (especially fluindione and warfarin) can be improved by dose adjustment algorithms, taking into account the results of International Normalized Ratio (INR). Reminders at the point of care, computerized or not, have been demonstrated to be effective in changing physicians prescription behavior.However, few studies have addressed the benefit of personalized reminders versus non personalized reminders, whereas the personalized reminders require more development to access patient record data and integrate with the computerized physician order entry system. The Hospital Information System of George Pompidou European Hospital integrates an electronic medical record, lab test and drugs order entry system. This system allows to evaluate such reminders and to consider their implementation for routine use as well as the continuous evaluation of their impact on medical practice quality indicators. The objective of this study is to evaluate the impact of two types of reminders on overtreatment by oral anticoagulant: a simple reminder of text formatted dose adjustment table and a personalized recommendation for oral anticoagulant dose and next date of INR control, adapted to patient data. Both types of reminders appear to the physician at the moment of drug ordering. (+info)
Characterization of the T-cell response in a patient with phenindione hypersensitivity.
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The oral anticoagulant phenindione [2-phenyl-1H-indene-1,3(2H)-dione] is associated with hypersensitivity reactions in 1.5 to 3% of patients, the pathogenesis of which is unclear. We describe a patient who developed a severe hypersensitivity reaction that involved both the skin and lungs. A lymphocyte transformation test showed proliferation of T-cells from the hypersensitive patient, but not from four controls on exposure to phenindione in vitro. Drug-specific T-cell clones were generated and characterized in terms of their phenotype, functionality, and mechanism of antigen presentation. Forty-three human leukocyte antigen class II restricted CD4(+) alphabeta T-cell clones were identified. T-cell activation resulted in the secretion of interferon-gamma and interleukin-5. Five of seven clones proliferated with phenindione alone, whereas two clones also proliferated with 2-phenylindene. Certain T-cell clones were also stimulated by R- and S-warfarin; computer modeling revealed that warfarin can adopt a phenindione-like structure. Phenindione was presented to T-cells via two pathways: first, bound directly to major histocompatibility complex and second, bound to a processed peptide. Our data show that CD4(+) T-cells are involved in the pathophysiology of phenindione hypersensitivity. There may be cross-sensitivity with warfarin in some phenindione hypersensitive patients. (+info)