Fondaparinux - data on efficacy and safety in special situations. Thromb Res. 2012;129:407-417. [PMID: 22133273 DOI: 10.1016/j.thromres.2011.10.037]

Novel Antithrombotic Agents in Pregnancy Anticoagulants and Antiplatelet Agents

Increasing rates of thromboembolic complications have required increasing use of anticoagulant and antiplatelet agents during and after pregnancy. Furthermore, thromboembolism is both a cause and a complication of severe maternal morbidity requiring intensive care. As a consequence, almost all patients admitted to intensive care units receive an anticoagulant or an antiplatelet agent (or both) for either treatment or prevention of thromboembolism. In this review, we summarize commonly used anticoagulants and antiplatelet agents and outline the potential role of newly developed (novel) antithrombotic agents for pregnant and postpartum patients.

Serpins in Hemostasis as Therapeutic Targets for Bleeding or Thrombotic Disorders

Bleeding and thrombotic disorders result from imbalances in coagulation or fibrinolysis, respectively. Inhibitors from the serine protease inhibitor (serpin) family have a key role in regulating these physiological events, and thus stand out as potential therapeutic targets for modulating fibrin clot formation or dismantling. Here, we review the diversity of serpin-targeting strategies in the area of hemostasis, and detail the suggested use of modified serpins and serpin inhibitors (ranging from small-molecule drugs to antibodies) to treat or prevent bleeding or thrombosis.

Retrospective Analysis of Fondaparinux and Low-Molecular-Weight Heparin in the Treatment of Women With Recurrent Spontaneous Abortion

BACKGROUND

To compare the clinical efficacy of fondaparinux and LMWH and provide clinical evidence for the effectiveness of fondaparinux in the treatment of recurrent spontaneous abortion caused by PTS.

METHODS

A retrospective analysis was conducted for 120 patients diagnosed with a recurrent spontaneous abortion caused by PTS in Qingdao Jinhua Women's Hospital from March 2019 to April 2020. The patients were divided into two groups: 68 cases in the control group, treated with LMWH, 52 cases in the observational group, treated with fondaparinux. The pregnancy outcomes and adverse reactions between the two groups of recurrent miscarriage patients were compared.

RESULTS

No significant difference was detected in the general data between the two groups of patients before treatment (P>0.05). In the observational group, the R value was increased, and the α and MA values were decreased after three months of treatment compared to those before treatment (P<0.05). In the control group, the R value was increased, and the MA value was decreased after three months of treatment compared to those before treatment (P<0.05). After treatment, no significant difference was observed in the pregnancy outcome between the two groups (P>0.05). The total adverse reaction rate of the fondaparinux group was lower than that of the LMWH group (P<0.05).

CONCLUSIONS

In this study, no significant difference was detected in the pregnancy outcome between fondaparinux and LMWH in the treatment of recurrent spontaneous abortion caused by PTS, but fondaparinux had a low occurrence rate of adverse reactions and high safety.

Programmable One-Pot Synthesis of Heparin Pentasaccharide Fondaparinux

The clinically approved Fondaparinux (Arixtra) has been used for the treatment of deep vein thrombosis and acute pulmonary embolism since 2002 and is considered to be better than the low-molecular weight heparin in terms of anticoagulation response, duration of action, and biosafety. However, the synthetic methods previously developed for its manufacture are relatively complicated, thus restricting its extensive use. We report here a potentially scalable and programmable one-pot synthesis of Fondaparinux using the [1,2,2] strategy and designed thioglycosides with well-defined reactivity as building blocks.

Multiple subcutaneous haematomas of the legs causing skin necrosis in an elderly patient affected by corticosteroid-induced skin atrophy: Case report and review of literature

Corticosteroid-induced skin atrophy (CISA) consists of a thinning of the skin and subcutaneous tissues, representing the natural consequence of a prolonged glucocorticosteroids use, both systemic as well as topical. It is characterised by the loss of elasticity and skin thickness, associated with an increased skin fragility leading to ecchymoses, haematomas, and steroid purpura. The management of CISA is a challenge for physicians, as the pathology is reversible in a minimal percentage of cases and only after a short topical steroid or low-dose course therapy. Often wounds with large loss of substance represent the more common complication, after a surgical drainage which is often necessary. Skin necrosis with compartment syndrome of a leg is another potential risk for these patients. Here, we report a case of an elderly patient affected by multiple subcutaneous haematomas of the legs causing skin necrosis, arisen after the use of anticoagulants for a deep venous thrombosis. The patient was successfully treated with surgical drainage, negative pressure wound therapy (NPWT), and porcine xenograft with no complications. Finally, we discuss the evidence of the current literature on topic.

Surfing the Blood Coagulation Cascade: Insight into the Vital Factor Xa

Factor Xa (FXa) plays a key role in haemostasis, it is a central part of the blood coagulation cascade which catalyzes the production of thrombin and leads to clot formation and wound closure. Therefore, FXa is an attractive target for the development of new anticoagulant agents. In this review, we will first describe the molecular features of this fundamental protein in order to understand its mechanism of action, an essential background for the design of novel inhibitors by means of synthetic organic chemistry or using peptides obtained from recombinant methodologies. Then, we will review the current state of the synthesis of novel direct FXa inhibitors along with their mechanisms of action. Finally, approved reversal agents that aid in maintaining blood haemostasis by using these commercial drugs will also be discussed.

Treatment of bleeding complications in patients on anticoagulant therapy

Anticoagulant therapy is often refrained from out of fear of hemorrhagic complications. The most frequent type of major bleeding is gastrointestinal, but intracranial hemorrhage has the worst prognosis. Management of these complications in patients on anticoagulants should follow the same routines as for nonanticoagulated patients, as described here with the previously mentioned bleeds as examples. In addition, for life-threatening or massive hemorrhages, reversal of the anticoagulant effect is also crucial. Adequate reversal requires information on which anticoagulant the patient has taken and when the last dose was ingested. Laboratory data can be of some help, but not for all anticoagulants in the emergency setting. This is reviewed here for the different types of anticoagulants: vitamin K antagonists, heparins, fondaparinux, thrombin inhibitors and factor Xa inhibitors. Specific antidotes for the latter are becoming available, but supportive care and nonspecific support for hemostasis with antifibrinolytic agents or prothrombin complex concentrates, which are widely available, should be kept in mind.

Targeting heparin and heparan sulfate protein interactions

Heparin and heparan sulfate glycosaminoglycans are long, linear polysaccharides that are made up of alternating dissacharide sequences of sulfated uronic acid and amino sugars. Unlike heparin, which is only found in mast cells, heparan sulfate is ubiquitously expressed on the cell surface and in the extracellular matrix of all animal cells. These negatively-charged glycans play essential roles in important cellular functions such as cell growth, adhesion, angiogenesis, and blood coagulation. These biomolecules are also involved in pathophysiological conditions such as pathogen infection and human disease. This review discusses past and current methods for targeting these complex biomolecules as a novel therapeutic strategy to treating disorders such as cancer, neurodegenerative diseases, and infection.

Chemoenzymatic synthesis of unmodified heparin oligosaccharides: cleavage of p-nitrophenyl glucuronide by alkaline and Smith degradation

A heparin oligosaccharide having a completely natural structure was successfully synthesized through a chemoenzymatic approach using an unnatural glycosyl acceptor, p-nitrophenyl glucuronide (GlcA-pNP). The use of an inexpensive and commercially available GlcA-pNP acceptor facilitates oligosaccharide recovery and purification on C-18 resin during chemoenzymatic synthesis. Oligosaccharide chain extension and modification afforded a heptasaccharide with gluconic acid residues at its reducing and non-reducing ends. Treatment with periodate oxidation followed by Smith degradation or alkaline elimination resulted in the selective cleavage of vicinal diol-containing glucuronic acid residues affording highly sulfated heparin pentasaccharides having a completely natural structure. This methodology should facilitate the chemoenzymatic synthesis of a family of highly sulfated heparin oligosaccharides with unmodified structures for biological evaluation.

Inactivated antithrombins as fondaparinux antidotes: a promising alternative to haemostatic agents as assessed in vitro in a thrombin-generation assay

In the absence of specific antidote to fondaparinux, two modified forms of antithrombin (AT), one recombinant inactive (ri-AT) and the other chemically inactivated (chi-AT), were designed to antagonise AT-mediated anticoagulants, e. g. heparins or fondaparinux. These inactive ATs were previously proven to effectively neutralise anticoagulant activity associated with heparin derivatives in vitro and in vivo, as assessed by direct measurement of anti-FXa activity. This study was undertaken to evaluate in vitro the effectivity of inactive ATs to reverse anticoagulation by heparin derivatives and to compare them with non-specific fondaparinux reversal agents, like recombinant-activated factor VII (rFVIIa) or activated prothrombin-complex concentrate (aPCC), in a thrombin-generation assay (TGA). Addition of fondaparinux (3 µg/ml) to normal plasma inhibited thrombin generation by prolonging lag time (LT) as much as 244 % and lowering endogenous thrombin potential (ETP) to 17 % of their control (normal plasma) values. Fondaparinux-anticoagulant activity was reversed by ri-AT and chi-AT, as reflected by the corrections of LT up to 117 % and 114 % of its control value, and ETP recovery to 78 % and 63 %, respectively. Unlike ri-AT that had no effect on thrombin generation in normal plasma, chi-AT retained anticoagulant activity that minimises its reversal capacity. However, both ATs were more effective than rFVIIa or aPCC at neutralising fondaparinux and, unlike non-specific antidotes, inactive ATs specifically reversed AT-mediated anticoagulant activities, as suggested by their absence of procoagulant activity in anticoagulant-free plasma.

Formal Synthesis of Anticoagulant Drug Fondaparinux Sodium

The practical formal synthesis of the anticoagulant drug fondaparinux sodium 1 was accomplished using an optimized modular synthetic strategy. The important pentasaccharide 2, a precursor for the synthesis of fondaparinux sodium, was synthesized on a 10 g scale in 14 collective steps with 3.5% overall yield from well-functionalized monosaccharide building blocks. The strategy involved a convergent [3 + 2] coupling approach, with excellent stereoselectivity in every step of glycosylation from the monosaccharide building blocks. Efficient routes to the syntheses of these fully functionalized building blocks were developed, minimizing oligosaccharide stage functional-group modifications. The syntheses of all building blocks avoided rigorous reaction conditions and the use of expensive reagents. In addition, common intermediates and a series of one-pot reactions were employed to enhance synthetic efficiency, improving the yield considerably. In the monosaccharide-to-oligosaccharide assembly reactions, cheaper activators (e.g., NIS/TfOH, TESOTf, and TfOH) were used to facilitate highly efficient glycosylations. Furthermore, crystallization of several monosaccharide and oligosaccharide intermediates significantly simplified purification procedures, which would be greatly beneficial to the scalable synthesis of fondaparinux sodium.

Prolonged use of fondaparinux for perioperative bridging: a case report of a patient with mechanical heart valve and heparin-induced thrombocytopenia

WHAT IS KNOWN AND OBJECTIVES

Current guidelines provide no recommendations on perioperative bridging for patients after mechanical heart valve replacement (MHVR) who also have a history of heparin-induced thrombocytopenia (HIT). We present a successful case of prolonged bridging with fondaparinux in a 69-year-old Chinese woman.

CASE SUMMARY

The patient presented to our department with the aim for radical resection of oesophageal cancer. Fondaparinux has been administered alone at 2·5 mg subcutaneously once daily for 24 days during the interruption of warfarin perioperatively. There were no signs or symptoms of thromboembolic or bleeding throughout and after her hospitalization.

WHAT IS NEW AND CONCLUSION

Fondaparinux may offer an option for management of the patients with MHVR who cannot use heparin products, but further clinical investigations are warranted.

Venous Thromboembolism in Patients Diagnosed With Lung Cancer

PURPOSE

Considering the high prevalence of lung cancer, our purpose was to summarize the existing literature to identify the several factors that contribute to the increased risk of venous thromboembolism (VTE) in patients with lung cancer and to analyze the current recommendations for thromboprophylaxis and treatment of VTE in those patients.

METHODS

We searched the Medline and EMBASE databases from February 1985 to February 2014 to identify retrospective and prospective randomized controlled studies that investigate one or more risk factors for VTEs in patients with lung cancer.

RESULTS

A VTE is a major complication for patients diagnosed with lung cancer. The risk factors for VTE events in patients with lung cancer consist of cancer-related (histological type and stage of cancer), treatment-related (surgery, chemotherapy, angiogenic agents, and supportive care agents), and patient-related factors (comorbidities, immobility, performance status, and prior thrombosis). Low-molecular-weight heparins are recommended for long-term treatment of cancer-associated thrombosis. Duration of anticoagulant therapy beyond 6 months should be based on individual clinical evaluation. Thromboprophylaxis for patients with lung cancer during hospitalization and immediate postoperative period is well established.

CONCLUSIONS

Efforts to assess thrombotic risk in patients with lung cancer may improve therapeutic and preventive strategies in the future, with final goal to minimize the burden and consequences of thrombotic events in patients with lung cancer.

How I treat catastrophic thrombotic syndromes

Catastrophic thrombotic syndromes are characterized by rapid onset of multiple thromboembolic occlusions affecting diverse vascular beds. Patients may have multiple events on presentation, or develop them rapidly over days to weeks. Several disorders can present with this extreme clinical phenotype, including catastrophic antiphospholipid syndrome (APS), atypical presentations of thrombotic thrombocytopenic purpura (TTP) or heparin-induced thrombocytopenia (HIT), and Trousseau syndrome, but some patients present with multiple thrombotic events in the absence of associated prothrombotic disorders. Diagnostic workup must rapidly determine which, if any, of these syndromes are present because therapeutic management is driven by the underlying disorder. With the exception of atypical presentations of TTP, which are treated with plasma exchange, anticoagulation is the most important therapeutic intervention in these patients. Effective anticoagulation may require laboratory confirmation with anti–factor Xa levels in patients treated with heparin, especially if the baseline (pretreatment) activated partial thromboplastin time is prolonged. Patients with catastrophic APS also benefit from immunosuppressive therapy and/or plasma exchange, whereas patients with HIT need an alternative anticoagulant to replace heparin. Progressive thrombotic events despite therapeutic anticoagulation may necessitate an alternative therapeutic strategy. If the thrombotic process can be controlled, these patients can recover, but indefinite anticoagulant therapy may be appropriate to prevent recurrent events.

Heparin induced thrombocytopenia in critically ill: Diagnostic dilemmas and management conundrums

Thrombocytopenia is often noted in critically ill patients. While there are many reasons for thrombocytopenia, the use of heparin and its derivatives is increasingly noted to be associated with thrombocytopenia. Heparin induced thrombocytopenia syndrome (HITS) is a distinct entity that is characterised by the occurrence of thrombocytopenia in conjunction with thrombotic manifestations after exposure to unfractionated heparin or low molecular weight heparin. HITS is an immunologic disorder mediated by antibodies to heparin-platelet factor 4 (PF4) complex. HITS is an uncommon cause of thrombocytopenia. Reported incidence of HITS in patients exposed to heparin varies from 0.2% to up to 5%. HITS is rare in ICU populations, with estimates varying from 0.39%-0.48%. It is a complex problem which may cause diagnostic dilemmas and management conundrum. The diagnosis of HITS centers around detection of antibodies against PF4-heparin complexes. Immunoassays performed by most pathology laboratories detect the presence of antibodies, but do not reveal whether the antibodies are pathological. Platelet activation assays demonstrate the presence of clinically relevant antibodies, but only a minority of laboratories conduct them. Several anticoagulants are used in management of HITS. In this review we discuss the incidence, pathogenesis, diagnosis and management of HITS.

Pregnancy outcome after exposure to the novel oral anticoagulant rivaroxaban in women at suspected risk for thromboembolic events: a case series from the German Embryotox Pharmacovigilance Centre

BACKGROUND

New oral anticoagulants are increasingly used in women of childbearing age, but apart from one case report there is no published experience with rivaroxaban exposure during pregnancy.

METHODS

From October 2008 to December 2014, the German Embryotox Pharmacovigilance Centre identified 63 exposed pregnancies among 94 requests concerning rivaroxaban use during childbearing age. Follow-up included paediatric checks until 6 weeks after birth.

RESULTS

All pregnancies with completed follow-up were exposed at least during the first trimester. Treatment indications included venous thromboembolism, knee surgery, and atrial fibrillation. 37 pregnancies were prospectively ascertained and resulted in six spontaneous abortions, eight elective terminations of pregnancy, and 23 live births. All women had discontinued rivaroxaban after recognition of pregnancy, mostly in the first trimester, but in one woman treatment continued until gestational week 26. There was one major malformation (conotruncal cardiac defect) among the 37 prospectively ascertained pregnancies in a woman with complex medication and a previous foetus with cardiac malformation without exposure to rivaroxaban. Only one case of bleeding concerning a retrospective report of surgery for missed abortion was observed in our case series.

CONCLUSION

Our results might give reassurance to those women, who were inadvertently exposed to rivaroxaban in early pregnancy. However, our limited cohort size does not allow ruling out an increased malformation risk and does not support the use of rivaroxaban during pregnancy. In all cases of (inadvertent) rivaroxaban exposure during 1st trimester, anticoagulation regimen should be reconsidered and a detailed ultrasound assessment recommended to confirm normal foetal development.

Evaluation of Factor Xa-Specific Chromogenic Substrate Assays and the Determination of Pharmacokinetics of Fondaparinux

Fondaparinux (FPX), a synthesized factor Xa inhibitor, is one of the most popular anticoagulants for the prevention of postoperative venous thromboembolism (VTE). Although routine monitoring is not required, the bleeding adverse events cannot be neglected, and the measurement of anti-Xa activity is expected to be monitored. The primary purpose of this study is to evaluate the performances of 2 chromogenic assays for the detection of anti-Xa activity. Furthermore, the pharmacokinetics of FPX was examined using chromogenic assays. Anti-Xa activity was measured using 2 FPX-based chromogenic substrates (S2222 and STA-Liquid Anti-Xa). The reproducibility, detection limits, linearity, and correlations between the substrates were examined using normal plasma doped with low and high concentrations of FPX formulation. In addition, anti-Xa activity in 235 clinical samples from 164 cases treated was measured, and the pharmacokinetics of FPX was evaluated. Both of the tested substrates were capable of accurately measuring the anti-Xa activity of FPX, with a lower limit of 0.05 μg/mL and a coefficient of variation of less than 10%. The repeated administration of FPX induced a gradual but significant increase in the anti-Xa activity, which was negatively correlated with body weight and estimated glomerular filtration rate. No significant correlation between the anti-Xa activity and the occurrence of postoperative VTE or bleeding event was observed. Anti-Xa activity can be successfully determined using 2 chromogenic assays and automated biochemical analyzers. The clinical significance of anti-Xa activity monitoring should be examined in the future study.

Considerations for Systemic Anticoagulation in ESRD

In the setting of end-stage kidney disease, the incidence and risk for thrombotic events are increased and use of anticoagulants is common. The incidence of bleeding, however, is also a frequent issue and creates additional challenges in the management of anticoagulation therapy. Patients with end-stage renal disease are typically excluded from large clinical trials exploring the use of anticoagulants, which limits our knowledge of optimal management approaches. Furthermore, varying degrees of renal failure in addition to conditions that alter the pharmacokinetics of various anticoagulants or pharmacodynamic response may warrant alternative approaches to dosing. This review will explore systemic chronic anticoagulation therapy in the setting of chronic kidney disease where hemodialysis is required. Agents discussed include vitamin K antagonists, low-molecular-weight heparins, fondaparinux, oral factor Xa antagonists, and direct thrombin inhibitors. Clinical challenges, approaches to dosing regimens, and tools for measuring responses and reversal will be explored.

Use and impact of cardiac medication during pregnancy

ABSTRACT 

Cardiovascular disease is the most encountered cause of maternal death during pregnancy in the western world and an increase in maternal mortality due to cardiac causes has been observed. More women with congenital or acquired heart disease have the desire to become pregnant. Pregnancy is known to impose a major hemodynamic burden and also has impacts on the coagulation system. The risk of developing complications is clearly increased as compared with the normal population. For optimal management, it is crucial to have information on the effects of cardiac medications on the fetus. The focus of this article is to discuss the management of cardiac disease in pregnancy, as well as the known safety of cardiac medications for the mother and/or fetus.

Cancer-associated thrombosis: an overview

Venous thromboembolism (VTE) is a common complication in patients with malignant disease. Emerging data have enhanced our understanding of cancer-associated thrombosis, a major cause of morbidity and mortality in patients with cancer. In addition to VTE, arterial occlusion with stroke and anginal symptoms is relatively common among cancer patients, and is possibly related to genetic predisposition. Several risk factors for developing venous thrombosis usually coexist in cancer patients including surgery, hospital admissions and immobilization, the presence of an indwelling central catheter, chemotherapy, use of erythropoiesis-stimulating agents (ESAs) and new molecular-targeted therapies such as antiangiogenic agents. Effective prophylaxis and treatment of VTE reduced morbidity and mortality, and improved quality of life. Low-molecular-weight heparin (LMWH) is preferred as an effective and safe means for prophylaxis and treatment of VTE. It has largely replaced unfractionated heparin (UFH) and vitamin K antagonists (VKAs). Recently, the development of novel oral anticoagulants (NOACs) that directly inhibit factor Xa or thrombin is a milestone achievement in the prevention and treatment of VTE. This review will focus on the epidemiology and pathophysiology of cancer-associated thrombosis, risk factors, and new predictive biomarkers for VTE as well as discuss novel prevention and management regimens of VTE in cancer according to published guidelines.

Venous thromboembolism in cancer patients

OBJECTIVE

Venous thromboembolism (VTE) is a common complication in cancer patients. This review summarizes some of the most current knowledge of the epidemiology, risk factors, risk models, prophylaxis, and treatment of VTE in cancer patients.

METHODS

A literature search was conducted using PubMed; the search terms were venous thromboembolism, anticoagulation, and cancer. The bibliographies of pertinent studies and review articles were reviewed for additional references.

RESULTS

Venous thromboembolism is the second leading cause of death in patients with cancer. Cancer patients with VTE have poorer outcomes compared with noncancer patients with VTE. Many risk factors have been identified for VTE in patients with cancer that are patient-related, cancer-related, or treatment-related. Several biomarkers have been identified as potentially predictive of VTE risk. Risk assessment models such as the Khorana Risk Score stratify cancer patients with low, intermediate, and high risk of developing VTE based on baseline clinical and laboratory variables. Currently, enoxaparin is the preferred anticoagulant for initial VTE treatment in cancer patients. Low molecular weight heparin (LMWH) is recommended for both initial and long-term management of cancer-related VTE. Because the optimal duration of anticoagulation in cancer patients with VTE is unknown, the decision to extend anticoagulation requires weighing the risk of recurrent thrombosis against the risk of major bleeding. Patients with recurrent VTE can be bridged with LMWH, transitioned to full-dose LMWH or treated with LMWH dose escalation. While there is insufficient data to determine whether anticoagulation should be held in the setting of thrombocytopenia, full-dose anticoagulation is typically considered unsafe when platelets are < 50 000/μL. Inferior vena cava filters are currently recommended only for patients with acute VTE and contraindications to anticoagulation. Although management of catheter-associated thrombosis has not been well studied in cancer patients, it is recommended that cancer patients with catheter-associated thrombosis be treated with therapeutic anticoagulation for ≥ 3 months. Venous thromboembolism prophylaxis with UFH, LMWH, or fondaparinux is recommended in all hospitalized nonsurgical cancer patients and cancer patients undergoing major cancer surgery. Primary thromboprophylaxis is only currently recommended in high-risk ambulatory cancer patients such as multiple myeloma patients receiving thalidomide- or lenalidomide- based therapy.

CONCLUSION

Cancer-associated thrombosis is a common problem. As we begin to better understand the risk factors and biomarkers for cancer-associated VTE, we can further refine and develop risk-assessment models to determine those patients who would most likely benefit from anticoagulation. While LMWH products are generally preferred in cancer-related VTE, more research will continue to evolve our understanding of treatment and thrombopprophylaxis in cancer-associated VTE.

Anticoagulation in patients with impaired renal function and with haemodialysis. Anticoagulant effects, efficacy, safety, therapeutic options

Patients with impaired renal function are exposed to an increased risk for bleeding complications depending on the amount of the anticoagulant eliminated by the kidneys. The elimination of unfractionated heparins, vitamin K antagonists and argatroban is only minimally influenced by a reduced renal function. Low-molecular weight heparins, fondaparinux, danaparoid, hirudins and non-vitamin K antagonist oral anticoagulants (NOAC) cause a variably increased bleeding risk in renal impairment. Dose reductions are recommended for all of these anticoagulants in renal impairment, some are even contraindicated at certain levels of renal impairment. Their benefit over the conventional anticoagulants is preserved if renal dosing is employed. For end-stage renal disease patients specific treatment regimens are required.

Affinity-based design of a synthetic universal reversal agent for heparin anticoagulants

Heparin-based anticoagulant drugs have been widely used for the prevention of blood clotting during surgical procedures and for the treatment of thromboembolic events. However, bleeding risks associated with these anticoagulants demand continuous monitoring and neutralization with suitable antidotes. Protamine, the only clinically approved antidote to heparin, has shown adverse effects and ineffectiveness against low-molecular weight heparins and fondaparinux, a heparin-related medication. Alternative approaches based on cationic molecules and recombinant proteins have several drawbacks including limited efficacy, toxicity, immunogenicity, and high cost. Thus, there is an unmet clinical need for safer, rapid, predictable, and cost-effective anticoagulant-reversal agents for all clinically used heparins. We report a design strategy for a fully synthetic dendritic polymer-based universal heparin reversal agent (UHRA) that makes use of multivalent presentation of branched cationic heparin binding groups (HBGs). Optimization of the UHRA design was aided by isothermal titration calorimetry studies, biocompatibility evaluation, and heparin neutralization analysis. By controlling the scaffold's molecular weight, the nature of the protective shell, and the presentation of HBGs on the polymer scaffold, we arrived at lead UHRA molecules that completely neutralized the activity of all clinically used heparins. The optimized UHRA molecules demonstrated superior efficacy and safety profiles and mitigated heparin-induced bleeding in animal models. This new polymer therapeutic may benefit patients undergoing high-risk surgical procedures and has potential for the treatment of anticoagulant-related bleeding problems.

Venous thromboembolism after total joint arthroplasty: results from a Japanese multicenter cohort study

Introduction

Real-world evidence of the effectiveness of pharmacological thromboprophylaxis for venous thromboembolism (VTE) is limited. Our objective was to assess the effectiveness and safety of thromboprophylactic regimens in Japanese patients undergoing joint replacement in a real-world setting.

Method

Overall, 1,294 patients (1,073 females and 221 males) who underwent total knee arthroplasty (TKA) and 868 patients (740 females and 128 males) who underwent total hip arthroplasty (THA) in 34 Japanese national hospital organization (NHO) hospitals were enrolled. The primary efficacy outcome was the incidence of deep vein thrombosis (DVT) detected by mandatory bilateral ultrasonography up to post-operative day (POD) 10 and pulmonary embolism (PE) up to POD28. The main safety outcomes were bleeding (major or minor) and death from any cause up to POD28.

Results

Patients undergoing TKA (n = 1,294) received fondaparinux (n = 360), enoxaparin (n = 223), unfractionated heparin (n = 72), anti-platelet agents (n = 45), or no medication (n = 594). Patients undergoing THA (n = 868) received fondaparinux (n = 261), enoxaparin (n = 148), unfractionated heparin (n = 32), anti-platelet agents (n = 44), or no medication (n = 383). The incidence rates of sonographically diagnosed DVTs up to POD10 were 24.3% in patients undergoing TKA and 12.6% in patients undergoing THA, and the incidence rates of major bleeding up to POD28 were 1.2% and 2.3%, respectively. Neither fatal bleeding nor fatal pulmonary embolism occurred. Significant risk factors for postoperative VTE identified by multivariate analysis included gender (female) in both TKA and THA groups and use of a foot pump in the TKA group. Only prophylaxis with fondaparinux reduced the occurrence of VTE significantly in both groups. Propensity score matching analysis (fondaparinux versus enoxaparin) showed that the incidence of DVT was lower (relative risk 0.70, 95% confidence interval (CI) 0.58 to 0.85, P = 0.002 in TKA and relative risk 0.73, 95% CI 0.53 to 0.99, P = 0.134 in THA) but that the incidence of major bleeding was higher in the fondaparinux than in the enoxaparin group (3.4% versus 0.5%, P = 0.062 in TKA and 4.9% versus 0%, P = 0.022 in THA).

Conclusions

These findings indicate that prophylaxis with fondaparinux, not enoxaparin, reduces the risk of DVT but increases bleeding tendency in patients undergoing TKA and THA.

Trial registration

University Hospital Medical Information Network Clinical Trials Registry: UMIN000001366. Registered 11 September 2008.

Synthesis of the heparin-based anticoagulant drug fondaparinux

Fondaparinux, a synthetic pentasaccharide based on the heparin antithrombin-binding domain, is an approved clinical anticoagulant. Although it is a better and safer alternative to pharmaceutical heparins in many cases, its high cost, which results from the difficult and tedious synthesis, is a deterrent for its widespread use. The chemical synthesis of fondaparinux was achieved in an efficient and concise manner from commercially available D-glucosamine, diacetone α-D-glucose, and penta-O-acetyl-D-glucose. The method involves suitably functionalized building blocks that are readily accessible and employs shared intermediates and a series of one-pot reactions that considerably reduce the synthetic effort and improve the yield.

Pharmacologic prevention of venous thromboembolism in obese patients

Venous thromboembolism, a collective term for pulmonary embolism and deep venous thrombosis accounts for a large amount of mortality and morbidity in hospitalized patients. Obesity has been considered as an important risk factor for the development of venous thromboembolism. Anticoagulation with fixed doses of low molecular weight heparin, anti-factor Xa inhibitors and unfractionated heparin is widely used in hospitals and has shown to be an effective measure in prevention of venous thromboembolism in multiple major randomized, double-blind controlled trials. Appropriate dosing of anticoagulation in obese patients is still controversial, since obese and morbidly obese population of patients is consistently underrepresented or often excluded from most clinical trials, raising a concern for adequacy of standard dosing in this high risk population.

Diagnosis and management of pulmonary embolism in the elderly

Elderly patients are a population not only at particularly high risk of venous thromboembolism including pulmonary embolism (PE), but also at high risk of adverse clinical outcomes and treatment-related complications. Major progresses have been achieved in the diagnosis and treatment of PE over the last two decades. Nevertheless, some of elderly patients' specificities still represent important challenges in the management of PE in this population, from its suspicion to its diagnosis and treatment, and are discussed in this review. Perspectives for the future are from a diagnostic point of view the potential implementation of age-adjusted d-dimer cut-offs that will allow ruling out PE in a greater proportion of elderly patients without the need for thoracic imaging. From a therapeutic point of view, acquisition of post-marketing clinical experience with the use of new oral anticoagulants is still necessary, and in the meantime, these drugs should be prescribed with great caution in thoroughly selected elderly patients.

Fondaparinux as alternative anticoagulant to warfarin or low-molecular-weight heparin for recurrent venous thrombosis

OBJECTIVE

Recurrent venous thromboembolism (VTE) occurs in some patients despite treatment with the standard drugs, warfarin and low-molecular-weight heparin (LMWH). Fondaparinux is currently licensed by the Food and Drug Administration for the prophylaxis of deep-vein thrombosis in patients undergoing orthopedic or abdominal surgery and also in the treatment of VTE. Well-documented use of this agent beyond these indications and for prolonged periods is currently limited.

CASE SUMMARY

Two cases of "refractory" VTE, managed effectively with long-term fondaparinux are described. In the first case, a 43-year-old man developed recurrent thrombosis while receiving warfarin at a higher target international normalized ratio (INR) of 3 to 4. In the second case, a 45-year-old man developed recurrent thrombosis on once-daily dalteparin. Both the patients were successfully managed with fondaparinux for 36 months and 14 months, respectively, with no sign of recurrent thrombosis or adverse effects.

DISCUSSION

In patients with recurrent VTE, fondaparinux is effective as daily injections as much as twice-daily LMWH or warfarin maintained on higher therapeutic-range INRs. Although the exact mechanism for this effectiveness is not yet understood, it provides a useful alternative to the standard therapies. In addition, the side effect profile is also favorable for fondaparinux, in that it causes less thrombocytopenia and skin reactions in comparison with heparins.

CONCLUSION

Daily fondaparinux injections may be an effective antithrombotic agent in patients who develop recurrent VTE on anticoagulation with warfarin or LMWH.

The use of novel oral anticoagulants for thromboprophylaxis after elective major orthopedic surgery

Venous thromboembolism is a common cause of morbidity and mortality among patients undergoing elective orthopedic surgery. Due to the high incidence of venous thromboembolism in this setting, perioperative anticoagulation is the recommended approach for thromboprophylaxis. Low molecular weight heparin (LMWH), fondaparinux and warfarin are the agents commonly used for thromboprophylaxis. The well-recognized limitations of warfarin and the inconvenience and discomfort associated with the subcutaneous administration of low molecular weight heparin and fondaparinux inspired intense investigation to develop novel oral anticoagulants (NOACs) with more predictable pharmacokinetics, fewer drug interactions and no need for regular laboratory monitoring. Three NOACs have been demonstrated to be effective for thromboprophylaxis after total hip arthroplasty (THA) and total knee arthroplasty (TKA) in large randomized controlled trials. Here we review the pharmacology of rivaroxaban, dabigatran, and apixaban, summarize the major clinical trials of these agents in thromboprophylaxis after THA and TKA, and discuss the clinical factors to be considered by providers when selecting a NOAC for their patients.

Treatment of cancer-associated thrombosis

Therapeutic options for the management of venous thromboembolism (VTE) in patients with cancer remain very limited. Although low-molecular-weight heparin monotherapy has been identified as a simple and efficacious regimen compared with an initial parenteral anticoagulant followed by long-term therapy with a vitamin K antagonist, many clinical questions remain unanswered. These include optimal duration of anticoagulant therapy, treatment of recurrent VTE, and the treatment of patients with concurrent bleeding or those with a high risk of bleeding. Treatment recommendations from consensus clinical guidelines are largely based on retrospective reports or extrapolated data from the noncancer population with VTE, as randomized controlled trials focused on cancer-associated thrombosis are sorely lacking. Furthermore, with improvements in imaging technology and extended survival duration of patients with cancer, we are encountering more unique challenges, such as the management of incidental VTE. Clinicians should be aware of the limitations of the novel oral anticoagulants and avoid the use of these agents because of the paucity of evidence in the treatment of cancer-associated thrombosis.

Alternatives to standard unfractionated heparin for pediatric hemodialysis treatments

Despite advances in biomaterials and dialyzer design, thrombin generation occurs in the dialysis circuit because of platelet and leukocyte activation. As such, anticoagulation is required by the majority of children for successful dialysis to prevent clotting in the venous air detector and the capillary dialyzer, particularly for small children with slower blood flow rates. For many years unfractionated heparin has been the standard anticoagulant of choice, but is now being challenged by low-molecular-weight heparins (LMWHs) because they are simple to administer and reliable, particularly as the cost differential has been eroded. Alternative, nonheparin anticoagulants are more frequently available, but are often restricted to special circumstances: patients at high risk of hemorrhage; heparin allergy; or heparin-induced thrombocytopenia. These nonheparin alternatives are significantly more expensive than heparins, and may add a degree of complexity, such as citrate, which is a regional anticoagulant, although citrate-containing dialysate may permit short anticoagulant-free dialysis sessions. Systemic anticoagulants required for immune-mediated, heparin-induced thrombocytopenia are expensive and either have short half-lives, and therefore require continuous infusions, or prolonged half-lives, which, although allowing simple bolus administration, increases the risk of drug accumulation, over-dosage and hemorrhage.

Newer anticoagulants in critically ill patients

Critically ill patients are at increased risk for development of thrombosis. In addition, thrombosis is often unrecognized in this population. Furthermore, these patients are particularly susceptible to bleeding complications from anticoagulants. Herein the authors review the pharmacology, data from clinical trials, management of bleeding complications, and perioperative use of these agents in the intensive care unit population. Well-designed clinical trials are needed to improve our understanding of the safety and efficacy of these newer agents in critically ill patients.

Venous thromboembolism associated with pregnancy and hormonal therapy

Venous thromboembolism (VTE) is a major cause of maternal morbidity and mortality during or early after pregnancy and in women taking hormonal therapy for contraception or for replacement therapy. Post-thrombotic syndrome, including leg oedema and leg pain, is an unrecognized burden after pregnancy-related VTE, which will affect more than two of five women. Women with a prior VTE, a family history of VTE, certain clinical risk factors and thrombophilia are at considerably increased risk both for pregnancy-related VTE and for VTE on hormonal therapy. This review critically assesses the epidemiology and risk factors for pregnancy-related VTE and current guidelines for prophylaxis and treatment. We also provide information on the risk of VTE related to hormonal contraception and replacement therapy.