PubMed · 9813554
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M K Davies, A Hollman. 1998. Heparin.. https://doi.org/10.1136/hrt.80.2.120
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Theoretical aspects of the thermodynamic characterization of cooperative protein interactions with non-specific segments of a linear polymer lattice have been re-examined. This reconsideration has not only provided an alternative derivation of recursive expressions for the stoichiometry of random ligand binding prior to elimination of the parking problem but also extended that treatment to include binding with overlap of additional lattice units. The major obstacle to thermodynamic characterization of non-specific protein-polymer interactions is determination of the lattice capacity for ligand, which in turn defines the length of the polymer segment to which the protein binds. Although these parameters are most readily obtained from studies under conditions that ensure essentially stoichiometric interaction, the endpoint of such a titration is likely to reflect the irreversible rather than the equilibrium binding capacity of the lattice for ligand. Consideration of published results for spectrofluorometric titrations of the thrombin-heparin system under stoichiometric conditions in such terms has permitted their reconciliation with results of a later publication on the interaction under equilibrium conditions.
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BACKGROUND: Low molecular weight heparins have been shown to be effective and safe for prevention of venous thromboembolism. There is accumulating evidence that these new anticoagulants are also effective and safe for treatment of venous thromboembolism. OBJECTIVES: The objective of this review was to determine the effect of fixed-dose, subcutaneous low molecular weight heparins compared with adjusted-dose, intravenous or subcutaneous, unfractionated heparin for initial treatment of acute deep venous thrombosis or pulmonary embolism. SEARCH STRATEGY: Trials were identified from the Cochrane Peripheral Vascular Diseases Group trials register and LILACS. The reviewers contacted colleagues and representatives of pharmaceutical companies for additional information about trials. SELECTION CRITERIA: Randomised trials comparing fixed-dose, subcutaneous low molecular weight heparin with adjusted-dose, intravenous or subcutaneous, unfractionated heparin in patients with venous thromboembolism. DATA COLLECTION AND ANALYSIS: Two reviewers assessed trials for inclusion and quality, and extracted data independently. MAIN RESULTS: Fourteen studies with a total of 4754 patients were included. By the end of follow up in ten trials, thrombotic complications occurred in 86 (4.3%) of the 1998 patients treated with low molecular weight heparin, compared with 113 (5.6%) of the 2021 patients treated with unfractionated heparin (odds ratio 0.76, 95% confidence interval 0.57 to 1.01). In eight trials a reduction in thrombus size was shown by 60% treated with low molecular weight heparin and 54% treated with unfractionated heparin (odds ratio 0.77, 95% confidence interval 0.61 to 0.97). At the end of the initial treatment period, in all 14 of the trials, major haemorrhages occurred in 30 (1.3%) of the 2353 patients treated with low molecular weight heparin, compared with 51 (2.1%) of the 2401 patients treated with unfractionated heparin (odds ratio 0.60, 95% confidence interval 0.39 to 0.93). By the end of follow up in 11 trials, 135 (6.4%) of the 2108 patients treated with low molecular weight heparin had died, compared with 172 (8.0%) of the 2137 patients treated with unfractionated heparin (odds ratio 0.78, 95% confidence interval 0.62 to 0.99). Five studies with a total of 1636 patients examined proximal (above the knee) thrombosis; 814 treated with low molecular weight heparin and 822 with unfractionated heparin. A sub-analysis of these trials showed statistically significant reductions favouring the action of low molecular weight heparin in three areas: thrombotic complications; major haemorrhages; and overall mortality. By the end of follow up 39 (4. 8%) patients treated with low molecular weight heparin had thrombotic complications, compared with 64 (7.8%) treated with unfractionated heparin (odds ratio 0.60, 95% confidence interval 0. 40 to 0.89). Major haemorrhages occurred in 8 (1.0%) treated with low molecular weight heparin, compared with 68 (8.3%) treated with unfractionated heparin (odds ratio 0.44, 95% confidence interval 0. 21 to 0.95). By the end of follow up, 44 (5.4%) treated with low molecular weight heparin had died, compared with 68 (8.3%) treated with unfractionated heparin (odds ratio 0.64, 95% confidence interval 0.43 to 0.93). REVIEWER'S CONCLUSIONS: Low molecular weight heparin is at least as effective as unfractionated heparin in preventing recurrent venous thromboembolism, and significantly reduces the occurrence of major haemorrhage during initial treatment and overall mortality at the end of follow-up. It can be adopted safely as the standard therapy for deep venous thrombosis, and studies comparing individual low molecular weight heparins are merited.