A new era for anticoagulants

Direct oral anticoagulants and venous thromboembolism

Venous thromboembolism (VTE), consisting of deep vein thrombosis and pulmonary embolism, is a major clinical concern associated with significant morbidity and mortality. The cornerstone of management of VTE is anticoagulation, and traditional anticoagulants include parenteral heparins and oral vitamin K antagonists. Recently, new oral anticoagulant drugs have been developed and licensed, including direct factor Xa inhibitors (e.g. rivaroxaban, apixaban and edoxaban) and thrombin inhibitors (e.g. dabigatran etexilate). This narrative review focusses on the characteristics of these direct anticoagulants and the main results of published clinical studies on their use in the prevention and treatment of VTE.

Therapeutic potential of abalone and status of bioactive molecules: A comprehensive review

Marine organisms are increasingly being investigated as sources of bioactive molecules with therapeutic applications as nutraceuticals and pharmaceuticals. In particular, nutraceuticals are gaining popularity worldwide owing to their therapeutic potential and incorporation in functional foods and dietary supplements. Abalone, a marine gastropod, contains a variety of bioactive compounds with anti-oxidant, anti-thrombotic, anti-inflammatory, anti-microbial, and anti-cancer activities. For thousands of years different cultures have used abalone as a traditional functional food believing consumption provides health benefits. Abalone meat is one of the most precious commodities in Asian markets where it is considered a culinary delicacy. Recent research has revealed that abalone is composed of many vital moieties like polysaccharides, proteins, and fatty acids that provide health benefits beyond basic nutrition. A review of past and present research is presented with relevance to the therapeutic potential of bioactive molecules from abalone.

The evolution of anticoagulant therapy

Arterial and venous thromboembolism are leading causes of morbidity and mortality around the world. For almost 70 years, heparins (unfractionated heparin and low molecular weight heparins) and vitamin K antagonists have been the leading therapeutic medical options for the treatment and prevention of thromboembolic disorders. Nevertheless, the many limitations of these traditional anticoagulants have fuelled the search for novel agents over the past 15 years, and a new class of oral anticoagulants that specifically target activated factor X and thrombin has been developed and is now commercially available. In this narrative review, the evolution of anticoagulant therapy is summarised, with a focus on newer oral anticoagulants.

Cancer-associated thrombosis: investigating the role of new oral anticoagulants

Venous thromboembolism (VTE) is a common complication of cancer and has a significant impact on morbidity and mortality in patients with malignancies. Low molecular weight heparins (LMWHs) currently represent the drug of choice for both initial and long-term treatment of cancer-associated thrombosis. In recent years, however, a new class of novel oral anticoagulants (NOACs) inhibiting directly thrombin or activated factor X have been proposed as an alternative therapeutic option on the basis the results of subgroup analyses of phase III randomized controlled trials, including few cases of patients with cancer. After analysis of the available literature data, we conclude that although potentially interesting, future research specifically conducted in cancer patients is needed to clarify the role of these newer anticoagulant agents in prevention and treatment of cancer-related VTE.

Bioassay-guided fractionation of Melastoma malabathricum Linn. leaf solid phase extraction fraction and its anticoagulant activity

The aims of this study were to examine the bioactive component(s) responsible for the anticoagulant activity of M. malabathricum Linn. leaf hot water crude extract via bioassay-guided fractionation and to evaluate the effect of bioactive component(s) on the intrinsic blood coagulation pathway. The active anticoagulant fraction of F3 was subjected to a series of chromatographic separation and spectroscopic analyses. Furthermore, the effect of the bioactive component(s) on the intrinsic blood coagulation pathway was studied through immediate and time incubation mixing studies. Through Activated Partial Thromboplastin Time (APTT) assay-guided fractionation, Subfraction B was considered the most potent anticoagulant fraction. Characterisation of Subfraction B indicated that anticoagulant activity could partly be due to the presence of cinnamic acid and a cinnamic acid derivative. APTT assays for both the immediate and time incubation mixing were corrected back into normal clotting time range (35.4–56.3 s). In conclusion, cinnamic acid and cinnamic acid derivative from Subfraction B were the first such compounds to be discovered from M. malabathricum Linn. leaf hot water crude extract that possess anticoagulant activity. This active anticoagulant Subfraction B prolonged blood clotting time by causing factor(s) deficiency in the intrinsic blood coagulation pathway.

Direct thrombin inhibitors: patents 2002-2012 (Review)

Acute vascular diseases and other thromboses of the blood system constitute major health risks in developing countries. Thrombin plays a central role in blood coagulation, which is a crucial process involved in thrombosis. Direct thrombin inhibitors (DTIs) such as argatroban, dabigatran, dabigatran etexilate, lepirudin, desirudin and bivalirudin, which bind to thrombin and block its enzymatic activity, are widely and effectively used in the treatment of thromboembolic diseases. DTIs appear to overcome the disadvantages of indirect thrombin inhibitors such as unfractionated heparins (UFH). Although these DTIs show specific advantages over indirect inhibitors, they still present limitations, such as a narrow therapeutic window, and bleeding and anaphylaxis as side-effects. Novel anticoagulant drugs need thus to be developed to overcome these limitations. In the search for additional candidate agents with improved efficacy, safety and high bioavailability in oral administration, a high number of compounds has been identified, such as those derived from the tripeptide template D-Phe-Pro-Arg, aptamers and peptides isolated from blood-sucking animals. These candidates may prove the new agents of choice for the treatment of cardiovascular diseases.

Effect of Aqueous Extract and Fractions of Fagonia arabica on In Vitro Anticoagulant Activity

Fagonia arabica (FA) is a deobstruent and blood purifier, which possesses thrombolytic and antioxidant activities. In this study, the anticoagulant effects of FA and its derived fractions were evaluated. Plasma recalcification was performed with multisolvent extracts of FA and then with extracts prepared successively with increasing polarity of the solvents. Aqueous extract was the most potent anticoagulant extract, which was fractionated by thin-layer chromatography and column chromatography. Five fractions collected were checked for their anticoagulation effect. The most potent fraction was screened for phytoconstituents. Aqueous extract of FA is the most active anticoagulant (31 minutes). Results were statistically significant when compared to heparin (38 minutes) and saline (4.04 minutes; P > .001). The Fifth fraction (FA5), the most potent fraction (27 minutes), was found positive for flavonoids, saponin, tannin, triterpenoids, carbohydrates, reducing sugar, and monosaccharides. Aqueous FA and fraction FA5 were most active in in vitro anticoagulation, and any of the phytochemicals identified could be considered the active component.

Venous thromboembolism in cirrhosis: a review of the literature

Although hemorrhage has traditionally been regarded as the most significant hemostatic complication of liver disease, there is increasing recognition that hypercoagulability is a prominent aspect of cirrhosis. Identifying markers of coagulability and monitoring anticoagulation therapy in the setting of cirrhosis is problematic. The bleeding risk of venous thromboembolism (VTE) prophylaxis and treatment in patients with chronic liver disease is unclear and there are currently no recommendations to guide practice in this regard. In the present report, the mechanism of coagulation disturbance in chronic liver disease is reviewed with an examination of the evidence for an increased VTE risk in cirrhosis. Finally, the available evidence is assessed for prophylaxis and therapy of VTE in chronic liver disease, and the role it may play in decreasing clinical decompensation and improving survival.

New anticoagulants for treatment of venous thromboembolism

Venous thromboembolism (VTE) is a major cause of morbidity and mortality and anticoagulation is the cornerstone of treatment. Although effective, traditional anticoagulants (i.e., heparins and vitamin K antagonists) have significant limitations and there are several unmet needs. Therefore, new drugs have been developed, including direct factor Xa inhibitors (e.g., rivaroxaban, apixaban and edoxaban) and thrombin inhibitors (e.g., dabigatran etexilate). The characteristics of these agents and the main results of published clinical studies dealing with VTE treatment are critically summarized in this article.

Practical management of anticoagulants in family medicine after orthopedic surgery

In order to prevent postoperative venous thromboembolism, prophylactic anticoagulant therapy is routinely administered to hospitalized patients after total hip arthroplasty (THA) and total knee arthroplasty (TKA). However, after hospital discharge, anticoagulant therapy is primarily managed by a primary care physician (PCP). The agents traditionally used for this purpose are associated with certain limitations that affect anticoagulation management. The new, fixed-dose oral anticoagulants have predictable pharmacokinetic and pharmacodynamic profiles, no requirement for coagulation monitoring, and a low propensity for food and drug interactions. As a result, they have the potential to simplify and improve postoperative outcomes in patients who have undergone THA or TKA and allow for simpler management of anticoagulation in these patients. This article examines the clinical evidence for benefits of the new oral anticoagulants, discusses caveats regarding their appropriate use, and provides some guidance regarding bleeding management with these agents.

Costs and clinical consequences of suboptimal atrial fibrillation management

Atrial fibrillation (AF) places a considerable burden on the US health care system, society, and individual patients due to its associated morbidity, mortality, and reduced health-related quality of life. AF increases the risk of stroke, which often results in lengthy hospital stays, increased disability, and long-term care, all of which impact medical costs. An expected increase in the prevalence of AF and incidence of AF-related stroke underscores the need for optimal management of this disorder. Although AF treatment strategies have been proven effective in clinical trials, data show that patients still receive suboptimal treatment. Adherence to AF treatment guidelines will help to optimize treatment and reduce costs due to AF-associated events; new treatments for AF show promise for future reductions in disease and cost burden due to improved tolerability profiles. Additional research is necessary to compare treatment costs and outcomes of new versus existing agents; an immediate effort to optimize treatment based on existing evidence and guidelines is critical to reducing the burden of AF.

Inhibitors of propagation of coagulation: factors V and X

Cardiovascular diseases are still the most important cause of morbidity and mortality in western countries and antithrombotic treatment is nowadays widely used. Drugs able to reduce coagulation activation are the treatment of choice for a number of arterial and/or venous thromboembolic conditions. Some of the drugs currently used for this purpose, such as heparins (UFH or LMWH) and VKA, have limitations consisting of a narrow therapeutic window and an unpredictable response with the need of laboratory monitoring in order to assess their efficacy and safety. These drawbacks have stimulated an active research aimed to develop new drugs able to act on single factors involved in the coagulation network, with predictable response. Intense experimental and clinical work on new drugs has focused on synthetic agents, which could preferably be administered orally and at fixed doses. The most advanced clinical development with new anticoagulants has been achieved for those inhibiting FXa and some of them, like fondaparinux, are already currently used in clinical practice. Other agents, such as rivaroxaban, apixaban, otamixaban and edoxaban are under development and have already been studied or are currently under investigation in large scale phase III clinical trials for prevention and treatment of venous thromboembolism, atrial fibrillation and acute coronary syndromes. Some of them have proved to be more effective than conventional therapy. Data on some agents inhibiting FVa are still preliminary and some of these drugs have so far been considered only in patients with disseminated intravascular coagulation secondary to sepsis.

Old and new anticoagulant drugs: a minireview

Abstract The limits of traditional anticoagulants, such as heparin and warfarin, have prompted the search for new agents for prophylaxis and treatment of arterial and venous thromboembolism, including factor Xa and thrombin inhibitors. These agents can be given orally, and their most significant advantage is that no laboratory monitoring is needed. The anti-Xa inhibitor rivaroxaban and the direct thrombin inhibitor dabigatran etexilate are licensed for prophylaxis of venous thromboembolism (VTE) in high-risk orthopedic surgery. They are at least as safe and effective as heparins but much more expensive. Dabigatran, rivaroxaban, and other agents currently in the pipeline of clinical development have the potential to replace warfarin in the two most frequent indications for anticoagulation, i.e. secondary prophylaxis of VTE and atrial fibrillation. Prevention and treatment of coronary artery thrombosis in patients with ischemic heart disease is another area of investigation for the role of new anticoagulants. These drugs have the potential to meet some currently unmet needs of traditional anticoagulants, but available clinical data warrant confirmation and expansion. Lack of specific antidotes for anticoagulation reversal and the high cost are important limitations of their use.

Update on Rivaroxaban

Anticoagulants are recommended for the prevention and treatment of venous thromboembolism (VTE). The new anticoagulants which target specific factors in the coagulation cascade offer the advantage that they can be administered orally. These drugs seek to offer safe anticoagulation without the need for regular monitoring and frequent dose adjustment. Some of these newer drugs are in the advanced stages of clinical trials or have already completed them and thereby aim to provide more options in the management of thromboembolism. In the present review we discuss the currently available evidence supporting the use of these new anticoagulants, in particular rivaroxaban.

The association of factor V Leiden with myocardial infarction is replicated in 1880 patients with premature disease

AIMS

Gain-of-function variants of genes encoding coagulation factor V (F5 G1691A) and prothrombin (F2 G20210A) cause hypercoagulability and are established risk factors for venous thrombosis. A meta-analysis of 66,155 cases and 91,307 controls found that either polymorphism is associated with a moderately increased risk of coronary artery disease (CAD). Because genetic factors play a particularly important role when acute myocardial infarction (AMI) occurs in the young, we chose to replicate these results by investigating, in the frame of a case-control study, a large cohort of Italian patients who had AMI before the age of 45years.

METHODS AND RESULTS

In 1880 patients with AMI (1680 men and 210 women) and an equal number of controls, the minor A allele of F5 G1691A (2.6% frequency in cases and 1.7% in controls) was associated with an increased risk of AMI, the association remaining significant after adjustment for traditional risk factors (OR, 1.66; 95% CI, 1.15-2.38; P=0.006). The positive association with AMI for the minor A allele of F2 G20210A (2.5% frequency in cases and 1.9% in controls) did not reach statistical significance (OR, 1.32; 95% CI, 0.96-1.80; P=0.159).

CONCLUSIONS

In a large cohort of young AMI patients the gain-of-function variant F5 G1691A was associated with an increased risk of AMI. The findings on the variant F2 G20210A confirmed the previously reported results, but the association was statistically not significant. These data suggest that a number of young patients with AMI carry gene variants associated with a procoagulant phenotype.

Mechanism of hemostasis defects and management of bleeding in patients with acute coronary syndromes

The main cause of the hemostasis defects and related bleeding complications in patients with acute coronary syndromes (ACS) are the intake of multiple antithrombotic drugs, alone or concomitantly with invasive procedures such as coronary angiography and percutaneous coronary intervention (PCI). Antithrombotic drugs that impair several phases of hemostasis (platelet function, coagulation, and fibrinolysis) are causing bleeding particularly in elderly patients, in those underweight and with comorbidities such as renal insufficiency, diabetes, hypertension and malignancy. Identification of patients at high risk of bleeding is the most important preventive strategy, because the choice and dosages of drugs may to some extent be tailored to the degree of risk. Transfusions of blood products, which may become necessary in patients with major bleeding, should be used with caution, because they are associated with adverse cardiovascular events. To reduce the need of transfusion, the hemostatic drugs that decrease blood loss and transfusion requirements in cardiac surgery (antifibrinolytic amino acids, desmopressin, and recombinant factor VIIa) might be considered. However, the efficacy of these drugs in the control of bleeding complications is not unequivocally established in ACS and there is concern for an increased risk of thrombosis. In conclusion, evidence-based recommendations for the management of bleeding in patients with ACS are currently lacking, so that prevention through accurate assessment of the individual risk is the most valid strategy.