Low molecular weight heparin(oid)s. Clinical investigations and practical recommendations

Characterization of Danaparoid Complex Extractive Drug by an Orthogonal Analytical Approach

Danaparoid sodium salt, is the active component of ORGARAN, an anticoagulant and antithrombotic drug constituted of three glycosaminoglycans (GAGs) obtained from porcine intestinal mucosa extracts. Heparan sulfate is the major component, dermatan sulfate and chondroitin sulfate being the minor ones. Currently dermatan sulfate and chondroitin sulfate are quantified by UV detection of their unsaturated disaccharides obtained by enzymatic depolymerization. Due to the complexity of danaparoid biopolymers and the presence of shared components, an orthogonal approach has been applied using more advanced tools and methods. To integrate the analytical profile, 2D heteronuclear single quantum coherence (HSQC) NMR spectroscopy was applied and found effective to identify and quantify GAG component signals as well as those of some process signatures of danaparoid active pharmaceutical ingredient (API) batches. Analyses of components of both API samples and size separated fractions proceeded through the determination and distribution of the molecular weight (Mw) by high performance size exclusion chromatographic triple detector array (HP-SEC-TDA), chain mapping by LC/MS, and mono- (¹H and ¹³C) and bi-dimensional (HSQC) NMR spectroscopy. Finally, large scale chromatographic isolation and depolymerization of each GAG followed by LC/MS and 2D-NMR analysis, allowed the sequences to be defined and components to be evaluated of each GAG including oxidized residues of hexosamines and uronic acids at the reducing ends.

Prophylaxis of Venous Thrombosis in Neurocritical Care Patients: An Evidence-Based Guideline: A Statement for Healthcare Professionals from the Neurocritical Care Society

The risk of death from venous thromboembolism (VTE) is high in intensive care unit patients with neurological diagnoses. This is due to an increased risk of venous stasis secondary to paralysis as well as an increased prevalence of underlying pathologies that cause endothelial activation and create an increased risk of embolus formation. In many of these diseases, there is an associated risk from bleeding because of standard VTE prophylaxis. There is a paucity of prospective studies examining different VTE prophylaxis strategies in the neurologically ill. The lack of a solid evidentiary base has posed challenges for the establishment of consistent and evidence-based clinical practice standards. In response to this need for guidance, the Neurocritical Care Society set out to develop and evidence-based guideline using GRADE to safely reduce VTE and its associated complications.

Acute generalized exanthematous pustulosis from dalteparin

Heparins are widely used for the prophylaxis and treatment of venous thromboembolism. Several types of immunologically mediated reactions to heparins are reported, among them delayed-type hypersensitivity reactions with erythematous, infiltrated itchy plaques at injection sites. We describe a female patient, whose localized reaction from dalteparin was followed by a generalized rash presenting as acute generalized exanthematous pustulosis. Subcutaneous provocation testing showed cross-reactions to enoxaparin, certoparin, reviparin, nadroparin, danaparoid, fondaparinux, but not to pentosan polysulfate. The danaparoid and in a lesser extent the nadroparin patch showed pustules. Within the next day, a generalized rash developed. The upper aspect of her trunk was highly affected and showed discrete pustules. Despite the fact that low molecular-weight heparins are widely prescribed, this is, to our knowledge, the first observation of a pustular drug eruption attributable to this class of substances.

Comparison of the Vasodilatory Effect of Nadroparin, Enoxaparin, Dalteparin, and Unfractioned Heparin in Human Internal Mammary Artery

The aim of this study was to investigate whether the low-molecular-weight heparins (LMWHs) (eg, nadroparin, enoxaparin, and dalteparin) cause a vasodilatory effect in human internal mammary artery (IMA) and to further compare its effect with unfractioned heparin (UFH). Samples of redundant IMA obtained from 20 patients undergoing a coronary artery bypass graft surgery were cut into 3-mm-wide rings and suspended in 20-mL organ baths. Isometric tension was continuously measured with an isometric force transducer connected to a computer-based data acquisition system. LMWHs (0.5-6 U/mL) caused a concentration-dependent relaxation in the endothelium-intact human IMA rings, which were precontracted with Phe (10(-6) M) (P < 0.05). The vasodilator potency of LMWHs seems to be nearly similar while the maximal effect produced by LMWHs was less pronounced compared with that produced by UFH. Removal of endothelium totally abolished the responses of human IMA to LMWHs as well as UFH (P < 0.05). LMWHs-induced vasodilator effect was significantly attenuated by Nomega-nitro-L-arginine methyl ester (L-NAME, 10(-4) M) but not indomethacin (10(-5) M). Our results have shown that LMWHs cause a dose-dependent relaxation in human IMA but are less effective than that produced by UFH. The vasorelaxant effects induced by each of LMWH are nearly similar and seem to be via endothelium-dependent mechanisms, including generation of nitric oxide.

Unfractioned Heparin Produces Vasodilatory Action on Human Internal Mammary Artery by Endothelium-Dependent Mechanisms

The aim of this study was to investigate whether unfractioned heparin produces a direct vasodilatory effect on the human internal mammary artery (IMA) and the possible underlying mechanisms. Samples of redundant IMA were obtained from 20 patients undergoing coronary artery bypass graft surgery, and concentration-response curves to unfractioned heparin were constructed. Unfractioned heparin (0.5-6 U/mL) caused a concentration-dependent relaxation in the endothelium-intact human IMA rings precontracted with phenylephrine (10(-6) M). Removal of endothelium significantly inhibited the responses of human IMA to unfractioned heparin (P < 0.05). Nomega-Nitro-L-arginine methyl ester (L-NAME, 10(-4) M), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10(-5) M) and L-NAME (10(-4) M) plus ODQ (10(-5) M) partially reduced unfractioned heparin-induced vasodilatory response in endothelium-intact rings, whereas indomethacin alone had no effect. The vasodilatory effect of unfractioned heparin was completely inhibited by 40 mM KCl in the presence of L-NAME, ODQ, and indomethacin. These results clearly demonstrated that unfractioned heparin causes a concentration-dependent vasodilatation in human internal mammary artery, and this action seems to be via endothelium-dependent mechanisms, including generation of nitric oxide and endothelium-derived hyperpolarizing factor.

Comparison of unfractioned and low molecular weight heparin for prophylaxis of coagulopathies in 52 horses with colic: a randomised double-blind clinical trial

REASONS FOR PERFORMING STUDY

Unfractioned heparin (UFH) is widely used for prophylaxis of coagulation disorders, especially in colic-affected horses. However, it is accompanied by certain side effects.

OBJECTIVES

To compare the efficacy and side effects of unfractioned and low molecular weight heparin (LMWH) in horses with colic.

METHODS

The study was carried out as a randomised, double-blind, controlled clinical trial. Fifty-two horses with colic were treated subcutaneously with either UFH (heparin calcium, 150 iu/kg bwt initially, followed by 125 iu/kg bwt q. 12 h for 3 days and then 100 iu/kg bwt q. 12 h) or LMWH (dalteparin, 50 iu/kg bwt q. 24 h). All horses underwent daily physical examination including assessment of jugular veins, local reaction to heparin injections, haematological evaluation and coagulation profiles over up to 9 days.

RESULTS

The type of heparin used did not affect the general behaviour and condition. There were significantly more jugular vein changes in horses treated with UFH. Packed cell volume decreased significantly within the first few days of UFH treatment, but did not change significantly in horses treated with LMWH. Activated partial thromboplastin time (aPTT) and thrombin time (TT) were prolonged in horses treated with UFH but not in those treated with LMWH.

CONCLUSIONS

It was concluded that, in comparison to UFH, LMWH has markedly fewer side effects in horses.

POTENTIAL RELEVANCE

Therefore, LMWH is recommended for prophylaxis of coagulation disorders in colic patients.

Outpatient management of the chronically anticoagulated patient for elective surgery

With the appropriate use of preadmission clinics, "hospital in the home" programs, and alternatives to intravenous heparin, the majority of chronically anticoagulated patients can be managed as outpatients prior to elective surgery. The preoperative management depends on the original indication for long-term anticoagulation, the interval since the last thromboembolic event, and the extent and type of surgery planned. Only patients who are undergoing major surgery, and who have a high risk of recurrent thrombosis or embolism, require preoperative admission to hospital and conversion to an intravenous heparin regimen. Patients undergoing minor surgery may require no change to their oral anticoagulation. The remainder require cessation of oral anticoagulation and alternative thromboprophylaxis preoperatively, which can be achieved on an outpatient basis using low molecular weight heparin. Outpatient anticoagulation management requires a clear protocol that is understood and agreed to by all parties involved in the care of surgical patients perioperatively.

New antithrombin-based anticoagulants

Clinically used anticoagulants are inhibitors of enzymes involved in the coagulation pathway, primarily thrombin and factor Xa. These agents can be either direct or indirect inhibitors of clotting enzymes. Heparin-based anticoagulants are indirect inhibitors that enhance the proteinase inhibitory activity of a natural anticoagulant, antithrombin. Despite its phenomenal success, current anticoagulation therapy suffers from the risk of serious bleeding. The need for safer and more effective antithrombotic agents clearly exists. The past decade has seen enormous effort directed toward discovering and/or designing new molecules with anticoagulant activity. These new molecules can be classified into (a). antithrombin and its mutants, (b). natural polysaccharides, (c). synthetic modified heparins and heparin-mimics, (d). synthetic oligosaccharides, and (e). synthetic non-sugar antithrombin activators. This review focuses on these efforts in designing or discovering new molecules that act through the antithrombin pathway of anticoagulation.

Comparison of pharmacokinetic variables for two low-molecular-weight heparins after subcutaneous administration of a single dose to horses

OBJECTIVE

To determine pharmacokinetic variables and to evaluate the influence on clotting times after SC administration of single doses of dalteparin and enoxaparin to horses.

ANIMALS

5 healthy adult horses.

PROCEDURES

The study was designed as a 4-period crossover study. Each horse received a single SC injection of dalteparin (50 and 100 anti-Xa U/kg) and enoxaparin (40 and 80 anti-Xa U/kg). Plasma anti-Xa activities and clotting times were measured, and pharmacokinetic variables were determined. Absolute and relative maximal prolongation of clotting times was calculated, and correlation between plasma anti-Xa activities and clotting times was determined.

RESULTS

The SC administration of each of the doses of the 2 preparations was well tolerated. Time course of the anti-Xa activities could be described in a 1-compartment model. Comparison of low- and high-dose treatments revealed a disproportionate increase of the area under the plasma activity-time curve and prolongation of the terminal half-life, but the increase in maximum plasma activity was proportionate, and peak plasma concentrations corresponded with concentrations recommended in human medicine. There were only mild changes in activated partial thromboplastin time (aPTT), whereas the influence on thrombin time (TT) was greater, dose-dependent, and more variable. A weak-to-moderate correlation between aPTT and plasma anti-Xa activities and a moderate-to-strong correlation between TT and plasma anti-Xa activities were found.

CONCLUSIONS AND CLINICAL RELEVANCE

Pharmacokinetic and anticoagulatory properties of low-molecular-weight heparins in horses are similar to those found in humans. Once-daily SC administration of dalteparin or enoxaparin may be useful as an anticoagulatory treatment in horses.

GENERAL PHARMACOLOGIC TREATMENT OF ACUTE MYOCARDIAL INFARCTION

The general pharmacotherapeutic issues surrounding AMI are complex and expanding, especially with regard to treatment aimed at the [table: see text] culprit, coronary atherosclerotic thrombus. Basic, well-established therapy includes the routine administration of oxygen, nitroglycerin, aspirin, and at times morphine, with selected cases invoking caution with respect to these agents (e.g., nitroglycerin and the risk of hypotension in right ventricular infarction; contraindication to nitrolycerin in patients on sildenafil). Cardioprotective agents, especially beta-adrenergic antagonists, should be considered early in light of their demonstrated benefit; others, such as ACE inhibitors, need not be administered in the ED. Heparin, both UFH and the newer LMWHs, have well-established roles in acute coronary syndromes. The GP IIb/IIIa inhibitors are the most recent addition to the pharmacologic armamentarium; their role is evolving rapidly as research on this frontier continues. Table 2 reviews recommended dosing of selected agents in acute coronary syndromes.

Antithrombotic and thrombolytic therapy in acute cardiac care

This article explores the use of antithrombotic and thrombolytic therapy in acute cardiac care, and looks at traditional anticoagulant agents, newer antithrombin agents, thrombolytic agents, and others.

[Thromboembolism prevention in acute myocardial infarction]

The objectives were to identify risk factors for vein thromboembolic disease (VTD) among patients with acute myocardial infarction (AMI) and to analyse both quantitatively and qualitatively the performed thromboembolic prophylaxis. A cross-sectional study was carried out with all inpatients at the Coronary Unit at our hospital during 1998. The risk factors for thromboembolism included: inmobilization (79.2%), heart failure (33.2%) and age over 70 years (31%). VTD prophylaxis was performed in 86.9% of the time. Non-fractioned heparin (NFH) and low molecular weight heparins (LMWH), mostly nadroparine, were the most commonly used drugs at admission and at discharge, respectively. Overdosage and underdosage for NFH and LMWH, respectively, were observed. That patients received or not VTD prophylaxis was not influenced by thromboembolic risk factors.

Pathophysiology of heparin-induced thrombocytopenia. Clinical and diagnostic implications--a review

OBJECTIVE

This review of heparin-induced thrombocytopenia (HIT), the most frequent and dangerous side effect of heparin exposure, covers the epidemiology, pathophysiology, clinical presentation, diagnosis, and treatment of this disease syndrome.

DATA SOURCES AND STUDY SELECTION

Current consensus of opinion is given based on literature reports, as well as new information where available. A comprehensive analysis of the reasons for discrepancies in incidence numbers is given. The currently known mechanism is that HIT is mediated by an antibody to the complex of heparin->platelet factor 4, which binds to the Fc receptor on platelets. New evidence suggests a functional heterogeneity in the anti-heparin-platelet factor 4 antibodies generated to heparin, and a "superactive" heparin-platelet factor 4 antibody that does not require the presence of heparin to promote platelet activation or aggregation has been identified. Up-regulation of cell adhesion molecules and inflammatory markers, as well as preactivation of platelets/endothelial cells/leukocytes, are also considered to be related to the pathophysiology of HIT. Issues related to the specificity of currently available and new laboratory assays that support a clinical diagnosis are addressed in relation to the serotonin-release assay. Past experience with various anticoagulant treatments is reviewed with a focus on the recent successes of thrombin inhibitors and platelet GPIIb/IIIa inhibitors to combat the platelet activation and severe thrombotic episodes associated with HIT.

CONCLUSIONS

The pathophysiology of HIT is multifactorial. However, the primary factor in the mediation of the cellular activation is due to the generation of an antibody to the heparin-platelet factor 4 complex. This review is written as a reference for HIT research.

Formulary management of low molecular weight heparins

Low molecular weight heparins (LMWHs) are increasingly being utilised as anticoagulants in healthcare settings. These agents offer several advantages over standard unfractionated heparin. Indications for LMWHs include deep vein thrombosis and pulmonary embolism prophylaxis, deep vein thrombosis treatment, use in coronary procedures associated with a high risk for bleeding, and in acute coronary syndromes. Prior to being added to formularies, LMWHs should be evaluated for efficacy, safety and economic benefits over other anticoagulants. Institutions should be prepared to conduct their own economic assessments in the absence of readily available studies. There is clear evidence that LMWHs are cost saving or are at least cost effective as thromboprophylactic agents in major orthopaedic surgery. The economic benefits of LMWHs in other surgical situations is less clear. Consistent evidence from several countries indicate that LMWHs are cost saving as anticoagulants for the initial treatment of DVT. Further studies are needed to evaluate the efficacy, safety and economics of LMWHs in other conditions besides hip and knee arthroplasty and general surgery.

Low molecular weight heparin use during pregnancy: issues of safety and practicality

Low molecular weight heparin is an important agent for the treatment and prophylaxis against venous thromboembolism during pregnancy. It offers several distinct advantages over unfractionated heparin. A systematic search was performed of the literature review of low molecular weight heparin use in pregnancy and presents a practical approach to its use by obstetricians and internists.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader will be able to understand the pharmacology and the elimination of low molecular weight heparin, the potential side effects and how to appropriately monitor the drug, and the indications and management of the low molecular weight heparins during pregnancy.

Intrahepatic hemorrhage after use of low-molecular-weight heparin for total hip arthroplasty

Low-molecular-weight heparin (LMWH) has become a popular agent for prophylaxis against deep vein thrombosis and thromboembolic disease after total joint arthroplasty. LMWH allows for consistent dosing in postoperative patients without the need for laboratory monitoring. Hemorrhage is an uncommon but documented adverse reaction when using LMWH; however, intrahepatic hemorrhage has not been previously reported in conjunction with LMWH therapy. We report the case of a woman who suffered intrahepatic hemorrhage presenting with acute abdominal pain and vomiting after the use of enoxaparin for total hip arthroplasty.

Low-molecular-weight heparins

Low-molecular-weight heparins (LMWH) are a new group of parenteral anticoagulants. They represent a major clinical advance in anticoagulation since the identification of unfractionated heparin (UFH) in 1922 and the introduction of the synthetic coumarin derivative, warfarin, in 1948. Their predictable pharmacokinetics, increased bioavailability, and longer plasma half-life allow for once- or twice-daily dosing and eliminate the need for routine laboratory monitoring. This simplified administration stands to alter the clinical practice of anticoagulation. This review high-lights recent clinical trials and focuses on studies comparing LMWH with the other two major anticoagulants: UFH and coumadin.

Rational antithrombotic therapy and prophylaxis in elderly, immobile patients

The aging process is associated with increased coagulation and fibrinolysis parameters, resulting in an overall 'prethrombotic state'. This probably explains the increased baseline susceptibility of elderly patients to the development of thromboembolic disease. Additional factors such as major surgery or malignant disease multiply the risk of thromboembolism in this population. Even when adequate antithrombotic therapy is instituted, the mortality associated with thromboembolic disease remains considerable; this underlines the importance of adequate thromboembolic prophylaxis. At present, the use of low molecular weight heparins (LMWHs) in elderly immobile patients appears to be the most effective approach to prophylaxis. The use of compression stockings seems to be effective in the prevention of venous thrombosis, at least in moderate risk surgical patients. In patients undergoing orthopaedic surgery, additional prophylaxis (e.g. with an LMWH) is necessary. In the management of venous thrombosis, patients can initially be treated with a bodyweight-adjusted dosage of an LMWH. In patients with deep vein leg thrombosis or pulmonary embolism, oral anticoagulant therapy should be started as soon as possible, and should be continued for 6 months. However, before starting prophylaxis or therapy, an individual risk assessment should be performed in which the benefits and disadvantages are balanced. Most of the large trials that have studied the effects of thromboembolic prophylaxis have focused on postsurgical patients. However, it will be of great interest to develop more specific prophylactic and therapeutic regimens for different nonsurgical high risk subgroups of patients, particularly the elderly.

[Cost of low molecular weight heparin used in the prevention or therapy of thromboembolic disease]

Low-molecular-weight heparin are widely used for prophylaxis or curative treatment of thromboembolic disease. In France, low molecular weight heparin can only be used for the surgical prophylaxis (general and orthopaedic) of thromboembolic disease, for the initial treatment of deep vein thrombosis and in haemodialysis. In an economic approach we try to assess costing information which takes account of drug acquisition costs but also costs of drug administration and costs of drug therapy failure (failed prophylaxis, bleeding and recurrent thrombosis). At least, it has been argued that low molecular weight heparin may take it possible to discharge patients earlier and even to treat patients at home or as out-patients, thus creating further cost savings.

Differential interactions of heparin and heparan sulfate glycosaminoglycans with the selectins. Implications for the use of unfractionated and low molecular weight heparins as therapeutic agents

The selectins are calcium-dependent C-type lectins that bind certain sialylated, fucosylated, sulfated glycoprotein ligands. L-selectin also recognizes endothelial proteoglycans in a calcium-dependent manner, via heparan sulfate (HS) glycosaminoglycan chains enriched in unsubstituted glucosamine units. We now show that these HS chains can also bind P-selectin, but not E-selectin. However, while L-selectin binding requires micromolar levels of free calcium, P-selectin recognition is largely divalent cation-independent. Despite this, HS chains bound to P-selectin are eluted by ethylenediamine tetraacetic acid (EDTA), but only at high concentrations. Porcine intestinal mucosal (mast cell-derived) heparin (PIM-heparin) shows similar properties, with no binding to E-selectin, calcium-dependent binding of a subfraction to L-selectin and to P-selectin, and calcium-independent binding of a larger fraction to P-selectin, the latter being disrupted by high EDTA concentrations. Analysis of defined heparin fragment pools shows a size dependence for interaction, with tetradecasaccharides showing easily detectable binding to L- and P-selectin affinity columns. L-selectin binding fragments include more heavily sulfated and epimerized regions and, as with the endothelial HS chains, they are enriched in free amino groups. The P-selectin binding component includes this fraction as well as some less highly modified regions. Thus, endothelium-derived HS chains and mast cell-derived heparins could play a role in modulating the biology of selectins in vivo. Notably, P- and L-selectin binding to sialyl-Lewisx and to HL-60 cells (which are known to carry the native ligand PSGL-1) is inhibited by unfractionated pharmaceutical heparin preparations at concentrations 12-50-fold lower than those recommended for effective anticoagulation in vivo. In contrast, two low molecular weight heparins currently considered as clinical replacements for unfractionated heparin are much poorer inhibitors. Thus, patients undergoing heparin therapy for other reasons may be experiencing clinically significant inhibition of L- and P-selectin function, and the current switchover to low-molecular weight heparins may come at some loss of this effect. Low-dose unfractionated heparin should be investigated as a treatment option for acute and chronic diseases in which P- and L-selectin play pathological roles.