Advantages and limitations of the new anticoagulants

Unravelling Surface Modification Strategies for Preventing Medical Device-Induced Thrombosis

The use of biomaterials in implanted medical devices remains hampered by platelet adhesion and blood coagulation. Thrombus formation is a prevalent cause of failure of these blood-contacting devices. Although systemic anticoagulant can be used to support materials and devices with poor blood compatibility, its negative effects such as an increased chance of bleeding, make materials with superior hemocompatibility extremely attractive, especially for long-term applications. This review examines blood-surface interactions, the pathogenesis of clotting on blood-contacting medical devices, popular surface modification techniques, mechanisms of action of anticoagulant coatings, and discusses future directions in biomaterial research for preventing thrombosis. In addition, this paper comprehensively reviews several novel methods that either entirely prevent interaction between material surfaces and blood components or regulate the reaction of the coagulation cascade, thrombocytes, and leukocytes.

Regulation of mitochondrial function by hydroquinone derivatives as prevention of platelet activation

Platelet activation plays an essential role in the pathogenesis of thrombotic events in different diseases (e.g., cancer, type 2 diabetes, Alzheimer's, and cardiovascular diseases, and even in patients diagnosed with coronavirus disease 2019). Therefore, antiplatelet therapy is essential to reduce thrombus formation. However, the utility of current antiplatelet drugs is limited. Therefore, identifying novel antiplatelet compounds is very important in developing new drugs. In this context, the involvement of mitochondrial function as an efficient energy source required for platelet activation is currently accepted; however, its contribution as an antiplatelet target still has little been exploited. Regarding this, the intramolecular hydrogen bonding of hydroquinone derivatives has been described as a structural motif that allows the reach of small molecules at mitochondria, which can exert antiplatelet activity, among others. In this review, we describe the role of mitochondrial function in platelet activation and how hydroquinone derivatives exert antiplatelet activity through mitochondrial regulation.

A Descriptive Analysis of Direct Oral Anticoagulant Drugs Dosing Errors Based on Spontaneous Reports from the EudraVigilance Database

Direct oral anticoagulant drugs (DOACs) interfere with the coagulation process, thus improving patient care for those who require anticoagulant treatment. This study presents a descriptive analysis of adverse reactions (ADRs) attributed to DOAC dosage errors (overdose, underdose, and improper dose). The analysis was performed based on the Individual Case Safety Reports from the EudraVigilance (EV) database. Results show that data reported for rivaroxaban, apixaban, edoxaban, and dabigatran are mostly regarding underdosing (51.56%) compared to overdosing (18.54%). The most dosage error reports were identified for rivaroxaban (54.02%), followed by apixaban (33.61%). Dabigatran and edoxaban had similar percentages (6.26% and 6.11%, respectively) regarding dosage error reports. Since coagulation issues can become life-threatening events, and factors such as advanced age and renal failure can influence the pharmacokinetics of drugs, the correct usage of DOACs is of utmost importance for the management and prevention of venous thromboembolism. Thus, the collaboration and the complementarity of knowledge of physicians and pharmacists may offer a reliable solution for DOAC dose management and improve patient care.

Factor XI inhibitors: what should clinicians know

PURPOSE OF REVIEW

Factor XI (FXI) inhibitors were developed to address unmet needs and limitations of current anticoagulants and are currently being studied in several indications. In this paper, we review the rationale for the development of these agents and summarize what clinicians should know about drugs that target FXI.

RECENT FINDINGS

Patients with FXI deficiency may have a lower risk of venous thromboembolism and cardiovascular events and have a variable but generally mild bleeding diathesis. FXI has been proposed as a target for anticoagulants due to the potential for reduction in thrombosis with a lower risk of bleeding than current anticoagulant agents. Several classes of drugs that target FXI are under development, of which three classes (small molecule inhibitors, antisense oligonucleotides and monoclonal antibodies) have been studied in Phase II trials. At least three large Phase III trial programs are planned or are underway, and will study the efficacy and safety of FXI inhibitors in tens of thousands of patients across a variety of indications including atrial fibrillation, stroke and cancer-associated venous thromboembolism.

SUMMARY

FXI inhibitors were developed with the hope of attenuating thrombosis with reduced bleeding/impairment of haemostasis. These agents have shown promise in preliminary trials with a low rate of bleeding. Ongoing Phase III investigations will inform the utility of these agents in clinical practice.

Marine Biological Macromolecules and Chemically Modified Macromolecules; Potential Anticoagulants

Coagulation is a potential defense mechanism that involves activating a series of zymogens to convert soluble fibrinogen to insoluble fibrin clots to prevent bleeding and hemorrhagic complications. To prevent the extra formation and diffusion of clots, the counterbalance inhibitory mechanism is activated at levels of the coagulation pathway. Contrariwise, this system can evade normal control due to either inherited or acquired defects or aging which leads to unusual clots formation. The abnormal formations and deposition of excess fibrin trigger serious arterial and cardiovascular diseases. Although heparin and heparin-based anticoagulants are a widely prescribed class of anticoagulants, the clinical use of heparin has limitations due to the unpredictable anticoagulation, risk of bleeding, and other complications. Hence, significant interest has been established over the years to investigate alternative therapeutic anticoagulants from natural sources, especially from marine sources with good safety and potency due to their unique chemical structure and biological activity. This review summarizes the coagulation cascade and potential macromolecular anticoagulants derived from marine flora and fauna.

Impact of high altitude on the incidence of postoperative venous thromboembolism and its genetic susceptibility: A meta-analysis and systematic review

BACKGROUND

The effect of high-altitude (HA) on venous thromboembolism (VTE) and its mechanism remains ambiguous. To clarify this, we aimed to conduct a meta-analysis and systematic review to evaluate the incidence of VTE at HA and comparatively low altitude (LA) and figure out the intrinsic risk factors such as susceptibility genes of patients with VTE at HA.

METHODS

We selected studies that explored the risk factors for HA and VTE by searching PubMed, Embase, and Web of Science to analyze the impact of HA on VTE. All relevant studies before August 2021 were screened using the terms ([high altitude] OR [plateau] OR [mountain]) AND ([venous thromboembolism] OR [deep vein thrombosis] OR [pulmonary embolism]). Latest studies on the gene of HA-VTE patients were also summarized and analyzed.

RESULTS

Fifteen studies were eventually assessed, and the overall numbers of subjects with and without VTE were 1475 and 286,926 respectively. The overall incidence of VTE, deep vein thrombosis (DVT) and pulmonary embolism (PE) in the HA group was significantly higher than that in the LA group (P < 0.01). The overall incidence of VTE, DVT and PE in the HA group was significantly higher than that in the LA group at 30 days post operation (P < 0.05, P < 0.05 and P < 0.01, respectively). At 90 days post operation, incidence of VTE and PE in the HA group was higher than that in the LA group (P < 0.01and P < 0.01, respectively), but there was no difference in the incidence of DVT (P = 0.07). Regarding endogenous factors, the analysis of genes in patients with HA-VTE revealed numerous targeted genes such as ANG, ACE, lncRNA-LINC00 659/UXT-AS1 and GP4.

CONCLUSIONS

We observed a significant association between HA and the overall incidence of VTE and that at 30/90 days post operation, indicating that HA may be a risk factor for VTE.

New generation oral anticoagulant apixaban enhances embryo implantation by increasing integrin β3 expression in rats: A pilot study

OBJECTIVE

The first aim of this study was to investigate the effect of apixaban on endometrial receptivity via immunohistochemical investigation of integrin β3 expression in pregnant rats. The second aim was to compare the endometrial effects of both subcutaneous and oral anticoagulant drugs in terms of integrin β3 expressions.

METHODS

A total of 24 rats were selected for this study and divided into three equal groups as control, enoxaparin and apixaban groups. Subcutaneous enoxaparin and oral apixaban were applied for 15 days starting on the first day of pregnancy. On the 15th day of pregnancy, all rats were killed by cervical dislocation, and uterine horns, including pregnancy materials, were investigated for pregnancy success and endometrial receptivity by using immunohistochemical integrin β3 staining.

RESULTS

Living, viable fetuses were higher in the apixaban group compared to the control group (p=0.037). Intensity and universality of immunohistochemical staining of integrin β3 for endometrial stroma were detected statistically higher in the apixaban group than the other groups. (p=0.009 for intensity, p=0.014 for universality). Endometrial epithelial and myometrial integrin β3 expression were detected to be identical between the groups (p=0.3).

CONCLUSIONS

Apixaban enhances endometrial receptivity via increasing integrin β3 expression in rats. This result can lead to further studies to be done in the future.

Examining Adherence to Medication in Patients With Atrial Fibrillation: The Role of Medication Beliefs, Attitudes, and Depression

BACKGROUND/OBJECTIVES

This study examined whether beliefs about medicines, drug attitudes, and depression independently predicted anticoagulant and antiarrhythmic adherence (focusing on the implementation phase of nonadherence) in patients with atrial fibrillation (AF).

METHODS

This cross-sectional study was part of a larger longitudinal study. Patients with AF (N = 118) completed the Patient Health Questionnaire-8. The Beliefs about Medicines Questionnaire, Drug Attitude Inventory, and Morisky-Green-Levine Medication Adherence Scale (self-report adherence measure), related to anticoagulants and antiarrhythmics, were also completed. Correlation and multiple logistic regression analyses were conducted.

RESULTS

There were no significant differences in nonadherence to anticoagulants or antiarrhythmics. Greater concerns (r = 0.23, P = .01) were significantly, positively associated with anticoagulant nonadherence only. Depression and drug attitudes were not significantly associated with anticoagulant/antiarrhythmic adherence. Predictors reliably distinguished adherers and nonadherers to anticoagulant medication in the regression model, explaining 14% of the variance, but only concern beliefs (odds ratio, 1.20) made a significant independent contribution to prediction (χ = 11.40, P = .02, with df = 4). When entered independently into a regression model, concerns (odds ratio, 1.24) significantly explained 10.3% of the variance (χ = 7.97, P = .01, with df = 1). Regressions were not significant for antiarrhythmic medication (P = .30).

CONCLUSIONS

Specifying medication type is important when examining nonadherence in chronic conditions. Concerns about anticoagulants, rather than depression, were significantly associated with nonadherence to anticoagulants but not antiarrhythmics. Anticoagulant concerns should be targeted at AF clinics, with an aim to reduce nonadherence and potentially modifiable adverse outcomes such as stroke.

Left Atrial Appendage Thrombus Formation Despite Continuous Non-Vitamin K Antagonist Oral Anticoagulant Therapy in Atrial Fibrillation Patients Undergoing Electrical Cardioversion or Catheter Ablation: A Comparison of Dabigatran and Rivaroxaban

Left atrial appendage thrombus (LAAT) may be detected by transesophageal echocardiography (TOE) in patients with atrial fibrillation (AF) despite continuous anticoagulation therapy. We examined the factors predisposing to LAAT in patients treated with the anticoagulants dabigatran and rivaroxaban. We retrospectively evaluated 1,256 AF patients from three centres who underwent TOE before electrical cardioversion (n = 611, 51.4%) or catheter ablation (n = 645, 48.6%) from January 2013 to December 2019 and had been on at least three weeks of continuous dabigatran (n = 603, 48%) or rivaroxaban (n = 653, 52%) therapy. Preprocedural TOE diagnosed LAAT in 51 patients (4.1%), including 30 patients (5%) treated with dabigatran and 21 patients (3.2%) treated with rivaroxaban (p=0.1145). In multivariate logistic regression, predictors of LAAT in patients treated with dabigatran were non-paroxysmal AF (vs. paroxysmal AF) (OR = 6.2, p=0.015), heart failure (OR = 3.22, p=0.003), and a eGFR <60 ml/min/1.73 m² (OR = 2.65, p=0.012); the predictors in patients treated with rivaroxaban were non-paroxysmal AF (vs. paroxysmal AF) (OR = 5.73, p=0.0221) and heart failure (OR = 3.19, p=0.116). In ROC analysis of the dabigatran group, the area under the curve (AUC) for the CHA₂DS₂-VASc-RAF score was significantly higher (0.78) than those for the CHADS₂, CHA₂DS₂-VASc, and R₂CHADS₂ scores (0.67, 0.70, and 0.72, respectively). In the rivaroxaban group, the CHA₂DS₂-VASc-RAF score also performed significantly better (AUC of 0.77) than the CHADS₂, CHA₂DS₂-VASc, and R₂CHADS₂ scores (AUC of 0.66, 0.64, and 0.67, respectively). The risk of LAAT was the same for patients in both treatment groups. In all patients, non-paroxysmal AF or heart failure, and in patients treated with dabigatran an eGFR <60 ml/min/1.73 m², were independent predictors of LAAT. The new CHA₂DS₂-VASc-RAF scale had the highest predictive value for LAAT in the entire study population.

Primary Thromboprophylaxis in Ambulatory Cancer Patients: Where Do We Stand?

Venous thromboembolism (VTE), comprising deep-vein thrombosis and pulmonary embolism, is a frequent complication in ambulatory cancer patients. Despite the high risk, routine thromboprophylaxis is not recommended because of the high number needed to treat and the risk of bleeding. Two recent trials demonstrated that the number needed to treat can be reduced by selecting cancer patients at high risk for VTE with prediction scores, leading the latest guidelines to suggest such an approach in clinical practice. Yet, the interpretation of these trial results and the translation of the guideline recommendations to clinical practice may be less straightforward. In this clinically-oriented review, some of the controversies are addressed by focusing on the burden of VTE in cancer patients, discussing the performance of available risk assessment scores, and summarizing the findings of recent trials. This overview can help oncologists, hematologists, and vascular medicine specialists decide about thromboprophylaxis in ambulatory cancer patients.

Non-vitamin K oral anticoagulants (NOACs) in patients with stroke and atrial fibrillation

Patients with atrial fibrillation who had a previous transient ischemic attack or ischemic stroke had a significantly high risk of stroke recurrence and the introduction of oral anticoagulants should be mandatory. However, the long-term use of oral anticoagulants increases the risk of developing all types of intracranial hemorrhages. The advantages of non-vitamin K oral anticoagulants (NOACs) compared to warfarin are that they have a significantly lower risk for hemorrhagic stroke. They are preferred in elderly patients, those with small vessel disease, or those with previous intracerebral hemorrhage. The time of NOACs introduction after an ischemic stroke depends on its severity and the rule "1-3-6-12" days should be applied. The reintroduction of NOACs in patients with atrial fibrillation and previous intracerebral hemorrhage depends on its etiology and should be after about 4-8 weeks if the cardioembolic risk is high and the risk for intracranial hemorrhage small.

Evaluation of unmet clinical needs in prophylaxis and treatment of venous thromboembolism in at-risk patient groups: pregnancy, elderly and obese patients

BACKGROUND

Venous thromboembolism (VTE) accounts for an estimated 900,000 cases per year in the US alone and constitutes a considerable burden on healthcare systems across the globe.

OBJECTIVE

To understand why the burden is so high, qualitative and quantitative research was carried out to gain insights from experts, guidelines and published studies on the unmet clinical needs and therapeutic strategies in VTE prevention and treatment in three populations identified as being at increased risk of VTE and in whom VTE prevention and treatment were regarded as suboptimal: pregnant women, the elderly and obese patients.

METHODOLOGY

A gap analysis methodology was created to highlight unmet needs in VTE management and to discover the patient populations considered most at risk. A questionnaire was devised to guide qualitative interviews with 44 thrombosis and haemostasis experts, and a review of the literature on VTE in the specific patient groups from 2015 to 2017 was completed. This was followed by a Think Tank meeting where the results from the research were discussed.

RESULTS

This review highlights the insights gained and examines in detail the unmet needs with regard to VTE risk-assessment tools, biomarkers, patient stratification methods, and anticoagulant and dosing regimens in pregnant women, the elderly and obese patients.

CONCLUSIONS

Specifically, in pregnant women at high risk of VTE, low-molecular-weight heparin (LMWH) is the therapy of choice, but it remains unclear how to use anticoagulants when VTE risk is intermediate. In elderly patients, evaluation of the benefit of VTE prophylaxis against the bleeding risk is particularly important, and a head-to-head comparison of efficacy and safety of LMWH versus direct oral anticoagulants is needed. Finally, in obese patients, lack of guidance on anticoagulant dose adjustment to body weight has emerged as a major obstacle in effective prophylaxis and treatment of VTE.

Deprivation and inequalities lead to worse outcomes with dabigatran etexilate

INTRODUCTION Dabigatran etexilate is now prescribed for 51% of the patients receiving oral anticoagulation treatment in New Zealand. Its prescribing trends in relation to patient outcomes are, however, largely unknown for these patients. AIM To describe patient characteristics, effectiveness and safety of treatment with dabigatran etexilate in the New Zealand population. METHODS This retrospective cohort study used administrative health data for patients dispensed dabigatran etexilate between 1 July 2011 and 31 December 2015. Adverse events (haemorrhage) and treatment failure (thromboembolism or cerebrovascular accident) data were extracted and linked to patient-specific demographic data. Baseline patient characteristics were analysed with descriptive statistics to examine trends in dabigatran etexilate prescribing. Raw and adjusted hazard ratios (HRs), including covariates, were derived using Cox proportional hazard models. RESULTS In total, 52,413 patients were dispensed dabigatran etexilate. Multivariate analysis indicated the risk of haemorrhagic events were significantly increased for Māori (HR and 95% Confidence Interval (CI): 2.10 (1.54-2.86)) and Pacific Peoples (HR = 2.20 (1.49-3.24)); those aged >80 years (HR = 1.25 (1.08-1.43)); and more deprived populations in quintile 4 (HR = 1.24 (1.08-1.43)) and quintile 5 (HR = 1.30 (1.12-1.50)). There was an increased risk of thromboembolism and cerebrovascular accident among people aged >80 years (HR = 1.79 (1.49-2.15)). DISCUSSION Demographic factors are associated with adverse outcomes in patients treated with dabigatran etexilate. Targeted strategies are needed to prescribe dabigatran etexilate more appropriately in these populations.

Direct-Acting Oral Anticoagulants and Their Reversal Agents-An Update

Background: Over the last ten years, a new class of drugs, known as the direct-acting oral anticoagulants (DOACs), have emerged at the forefront of anticoagulation therapy. Like the older generation anticoagulants, DOACs require specific reversal agents in cases of life-threatening bleeding or the need for high-risk surgery. Methods: Published literature was searched, and information extracted to provide an update on DOACS and their reversal agents. Results: The DOACs include the direct thrombin inhibitor—dabigatran, and the factor Xa inhibitors—rivaroxaban, apixaban, edoxaban, and betrixaban. These DOACs all have a rapid onset of action and each has a predictable therapeutic response requiring no monitoring, unlike the older anticoagulants, such as warfarin. Two reversal agents have been approved within the last five years: idarucizumab for the reversal of dabigatran, and andexanet alfa for the reversal of rivaroxaban and apixaban. Additionally, ciraparantag, a potential “universal” reversal agent, is currently under clinical development. Conclusions: A new generation of anticoagulants, the DOACs, and their reversal agents, are gaining prominence in clinical practice, having demonstrated superior efficacy and safety profiles. They are poised to replace traditional anticoagulants including warfarin.

Cloning and purification of an anti-thrombotic, chimeric Staphylokinase in Pichia pastoris

There has been an increasing prevalence of cardiovascular diseases such as myocardial infarction and stroke in modern societies because of multiple lifestyle related issues like sedentariness and obesity, alcohol consumption and many more "life-style"factors. The FDA-approved thrombolytics such as Tissue Plasminogen Activator, Streptokinase etc. are used to lyse the clots in thrombotic disorders such as myocardial infarction, stroke etc. but re-occlusion and bleeding that are co-incident to their clinical usage are not addressed. Hence, there is need to develop thrombolytics having properties like increased fibrin clot specificity and thrombin inhibition capability to prevent re-occlusion. In the present work, a fusion protein construct containing two components i.e. Staphylokinase (SAK) and Epidermal Growth Factor (EGF) 4, 5, 6-like domains of human thrombomodulin (THBD) was expressed in Pichia pastoris after genetic optimization. SAK isolated from Staphylococcus aureus is a fibrin-specific plasminogen activator while EGF 4, 5, 6-like domains are reported to be responsible for imparting thrombin inhibition to human thrombomodulin, and therefore, expected could help prevent re-occlusion in the novel construct - SAK_EGF, which is a 43 kDa protein. After expression, it was purified (approx. 13-fold) using two-step purification protocol involving ion-exchange followed by Gel Filtration Chromatography (GFC). The functional characterization including plasminogen activation and thrombin inhibition showed that both the fusion partners viz. SAK and 4,5,6 EGF-like domains retained their respective activities after fusion, confirming it to be a bio-active construct. Thus, this engineered protein could be clinically promising due to the combinatorial effect of fibrin-specific thrombus lysis and prevention of re-occulusion.

Diagnostic accuracy of thromboelastometry and its correlation with the HPLC-MS/MS quantification test

The aim of the study was to evaluate the diagnostic accuracy of thromboelastometry for assessing rivaroxaban concentrations. The accuracy of thromboelastometry was compared with the high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method, which is the gold standard for drug plasma monitoring (the reference standard). Forty-six clinically stable patients were treated with 10, 15, or 20 mg of rivaroxaban once daily (OD group) or 15 mg twice a day (BID group) (no particular indication for treatment). Patient samples were collected 2 h after the use of the medication (peak) and 2 h before the next dose (trough). The rivaroxaban plasma concentrations were determined via HPLC-MS/MS, and thromboelastometry was performed using a ROTEM® delta analyzer. There were significant prolongations in clotting time (CT) for the 10, 15, and 20 mg of rivaroxaban treatments in the OD groups. In the 15 mg BID group, the responses at the peak and trough times were similar. At the peak times, there was a positive correlation between the plasma concentration of rivaroxaban and CT (Spearman correlation rho=0.788, P<0.001) and clot formation time (rho=0.784, P<0.001), and a negative correlation for alpha angle (rho=−0.771, P<0.001), amplitude after 5 min (rho=−0.763, P<0.001), and amplitude after 10 min (rho=−0.680, P<0.001). The CT presented higher specificity and sensitivity using the cut-off determined by the receiver characteristics curve. ROTEM has potential as screening tool to measure possible bleeding risk associated with rivaroxaban plasma levels.

Frequency of atrial thrombus formation in patients with atrial fibrillation under treatment with non-vitamin K oral anticoagulants in comparison to vitamin K antagonists: a systematic review and meta-analysis

BACKGROUND

To assess the frequency of left atrium/left atrial appendage (LA/LAA) thrombus under treatment with non-vitamin K oral anticoagulants (NOACs) in comparison with vitamin K antagonists (VKAs) in patients with non-valvular atrial fibrillation (AF).

METHODS

PubMed, Web of Science™, EMBASE and the Cochrane Library databases were searched for studies comparing NOACs with VKAs in AF patients who underwent diagnostic transoesophageal echocardiography (TEE).

RESULTS

A total of four trials were considered eligible and were included in the meta-analysis. Four RCTs comprising n = 2397 AF patients (NOACs: n = 1412, VKAs: n = 985) were included in the meta-analysis. The frequency of LA/LAA thrombus formation under treatment with NOACs was similar to VKAs [odds ratio (OR) 1.14, 95% confidence intervals (95% CIs) 0.97-1.65, p = 0.48]. Both treatment groups revealed an approximately 5% frequency of thrombus formation, although a precise calculation is not possible due to Simpson paradox. Indications of heterogeneity between the included trials were not found (χ2 test p = 0.99, I2 = 0%).

CONCLUSIONS

The findings of this meta-analysis suggest that NOACs are similar to VKAs regarding the frequency of LA/LAA thrombus in patients with AF. An unknown number of patients in the original studies did not receive sufficient anticoagulation for at least 3 weeks prior to TEE examination, and therefore the present results should be interpreted with caution. Systematic review registration- http://www.crd.york.ac.uk/PROSPERO . Unique identifier: PROSPERO CRD42017059293.

Methodological challenges in assessment of current use of warfarin among patients with atrial fibrillation using dispensation data from administrative health care databases

PURPOSE

Algorithms to define current exposure to warfarin using administrative data may be imprecise. Study objectives were to characterize dispensation patterns, to measure gaps between expected and observed refill dates for warfarin and direct oral anticoagulants (DOACs).

METHODS

Retrospective cohort study using administrative health care databases of the Régie de l'assurance-maladie du Québec. We identified every dispensation of warfarin, dabigatran, rivaroxaban, or apixaban for patients with AF initiating oral anticoagulants between 2010 and 2015. For each dispensation, we extracted date and duration. Refill gaps were calculated as difference between expected and observed dates of successive dispensation. Refill gaps were summarized using descriptive statistics. To account for repeated observations nested within patients and to assess the components of variance of refill gaps, we used unconditional multilevel linear models.

RESULTS

We identified 61 516 new users. Majority were prescribed warfarin (60.3%), followed by rivaroxaban (16.4%), dabigatran (14.5%), apixaban (8.8%). Most frequent recorded duration of dispensation was 7 days, suggesting use of pharmacist-prepared weekly pillboxes. The average refill gap from multilevel model was higher for warfarin (9.28 days, 95%CI:8.97-9.59) compared with DOACs (apixaban 3.08 days, 95%CI: 2.96-3.20, dabigatran 3.70, 95%CI: 3.56-3.84, rivaroxaban 3.15, 95%CI: 3.03-3.27). The variance of refill gaps was greater among warfarin users than among DOAC users.

CONCLUSIONS

Greater refill gaps for warfarin may reflect inadequate capture of the period covered by the number of dispensed pills recorded in administrative data. A time-dependent definition of exposure using dispensation data would lead to greater misclassification of warfarin than DOACs use.

Rivaroxaban prescribing in a Saudi tertiary care teaching hospital

Purpose

This drug utilization review (DUR) aimed to describe the use of rivaroxaban in a tertiary care teaching hospital and to audit the hospital physicians’ prescribing practice.

Methods

This study reviewed rivaroxaban prescriptions for patients admitted to a tertiary care teaching hospital in Riyadh, Saudi Arabia, between October 1, 2016 and January 15, 2017. It included all in-patients who received at least one dose of rivaroxaban, using data from the hospital’s health information system (HIS). Appropriateness of prescribing was evaluated based on documented indication, dosing according to the patient’s renal function for each approved indication, and restriction policy as per hospital department.

Results

During the study period, a total of 343 rivaroxaban prescriptions for 322 patients were identified. Overall, more than 56% of rivaroxaban prescriptions met at least one inappropriate criterion. Inappropriate dosing per patient’s creatinine clearance (CrCl) was recognized in 42% of rivaroxaban prescriptions with the majority of these prescriptions issued for lower doses in 82.9% of prescriptions and non-approved indications identified in 14% of rivaroxaban prescriptions.

Conclusions

The introduction of oral rivaroxaban represents a paradigm shift in anticoagulation management. Future longer, larger multi-center research is needed to identify the most effective interventions to enhance rivaroxaban knowledge translation and reduce the likelihood of inappropriate rivaroxaban prescribing and associated economic and side effects sequelae.

The Rate of Epistaxis Incidence in New-Generation Anticoagulants and Perioperative Approach in Otorhinolaryngological Practices

Nose bleeding is a common situation seen in otorhinolaryngological practices. One of the greatest risk factors in nose bleeding is the use of anticoagulant medicine. With the medicine developed in recent years, the risk of nose bleeding due to the frequent use of anticoagulant and antiagregant is gradually increasing.The purpose of this study is to determine the effects of especially new-generation anticoagulants on nose bleeding. In addition, the use and complications of new-generation anticoagulants and antiagregants have been compiled in light of information obtained from the literature.Three hundred forty patients whose follow-up is conducted by the cardiology department and who use oral antithrombocytic medicine have been included in the study. It has been determined that 15% of these patients use new-generation oral anticoagulants (Rivaroksaban, apiksaban, dabigatran, danaparoid) and the other patients are treated with conventional antithrombocytic treatment (Aspirin, Warfarin, Enoksaparin sodium). The rate of nose bleeding in patients who use classical anticoagulants has been observed to be 28%. In 30 of these patients who had nose bleeding, while cauterization and buffering by otorhinolaryngology specialists, major intervention has not been necessary for any of the patients. While bleeding has been observed in 26% of the patients who use new-generation anticoagulants, bleeding that required operational intervention has taken place in 2 patients. Bleedings have been stopped surgically through a large number of cauterization and buffering.While the new-generation anticoagulants cause lower rate of bleeding, it has been observed that controlling these bleedings is more difficult.

Identification and characterisation of novel inhibitors on extrinsic tenase complex from Bungarus fasciatus (banded krait) venom

Snake venoms are excellent sources of pharmacologically active proteins and peptides, and hence are potential sources of leads for drug developments. It has been previously established that krait (Bungarus genus) venoms contain mainly neurotoxins. A screening for anticoagulants showed that Bungarus fasciatus venom exhibits potent anticoagulant effect in standard clotting assays. Through sequential fractionation of the venom by size exclusion and high performance liquid chromatographies, coupled with functional screening for anticoagulant activities, we have isolated and purified two anticoagulant proteins, termed BF-AC1 ( Bungarus fasciatus anticoagulant 1) and BFAC2. They have potent inhibitory activities (IC50 of 10 nM) on the extrinsic tenase complex. Structurally, these proteins each has two subunits covalently held together by disulfide bond(s). The N-terminal sequences of the individual subunits of BF-AC1 and BF-AC2 showed that the larger subunit is homologous to phospholipase A2, while the smaller subunit is homologous to Kunitz type serine proteinase inhibitor. Functionally, in addition to their anticoagulant activity, these proteins showed presynaptic neurotoxic effects in both in vivo and ex vivo experiments. Thus, BF-AC1 and BF-AC2 are structurally and functionally similar to β-bungarotoxins, a class of neurotoxins. The enzymatic activity of phospholipase A2 subunit plays a significant role in the anticoagulant activities. This is the first report on the anticoagulant activity of β-bungarotoxins and these results expand on the existing catalogue of haemostatically active snake venom proteins.

Direct Oral Anticoagulant Drugs in Dental Clinical Practice

The direct oral anticoagulant drugs (DOAC) are generally safe and effective in several clinical settings including acute venous thromboembolic disease, prophylaxis in the postoperative setting, prevention of thromboembolism in patients with non-valvular atrial fibrillation, and in the management of acute coronary syndrome. The relatively short half-life, rapid onset of action, and predictable pharmacokinetics should simplify periprocedural use of the DOAC. The aim of this work is to propose and summarize periprocedural management of patients treated with the DOAC in dental practice and to inform about the principal specifications of this treatment.

Safety and efficacy of DOACs vs acenocoumarol in patients undergoing catheter ablation of atrial fibrillation

BACKGROUND

Thromboembolic complications can be life-threatening during atrial fibrillation (AF) catheter ablation. The aim of our study was to evaluate the safety and efficacy of continuous treatment using direct oral anticoagulants (DOACs) as an alternative to uninterrupted acenocoumarol for periprocedural anticoagulation.

HYPOTHESIS

Continuous treatment with DOACs has similar safety and efficacy compared to acenocoumarol.

METHODS

We enrolled 474 patients (mean age, 58 years; 68.4% male) undergoing AF catheter ablation between June 2013 and December 2016. All patients were equally assigned to take acenocoumarol (group 1, 136 patients) or DOACs (group 2, 338 patients) for ≥2 months before the procedure. We compared thromboembolic and bleeding complications between the 2 groups.

RESULTS

Our analysis showed no significant difference in major and minor complications between the 2 patient groups. Specifically, 3 of 136 patients (2.2%) using uninterrupted acenocoumarol had a major complication (1 patient [0.7%] had transient ischemic attack resolved 8 hours later, 1 [0.7%] had pericardial tamponade, and 1 [0.7%] had a subcapsular renal hematoma) and 2 patients (1.4%) had minor complications (1 [0.7%] pseudoaneurysm and 1 [0.7%] groin hematoma). In group 2, 1 of 338 patients (0.3%) had a major complication (transient ischemic attack). In the same group, 7 patients (2.1%) had a minor complication (1 patient [0.3%] presented with pseudoaneurysm, 4 [1.2%] with pericardial effusion <1 cm, 1 [0.3%] femoral arteriovenous fistula between the femoral artery and femoral vein, and 1 [0.7%] groin hematoma).

CONCLUSIONS

DOACs and acenocoumarol have similar safety and effectiveness regarding thromboembolic complications prevention without increasing bleeding complications.

ANMCO Position Paper: the use of non-vitamin K dependent new oral anticoagulant(s) in pulmonary embolism therapy and prevention

The new oral anticoagulants (NOACs) have radically changed the approach to the treatment and prevention of thromboembolic pulmonary embolism. The authors of this position paper face, in succession, issues concerning NOACs, including (i) their mechanism of action, pharmacodynamics, and pharmacokinetics; (ii) the use in the acute phase with the 'double drug single dose' approach or with 'single drug double dose'; (iii) the use in the extended phase with demonstrated efficacy and with low incidence of bleeding events; (iv) the encouraging use of NOACs in particular subgroups of patients such as those with cancer, the ones under- or overweight, with renal insufficiency (creatinine clearance > 30 mL/min), the elderly (>75 years); (v) they propose a possible laboratory clinical pathway for follow-up; and (vi) carry out an examination on the main drug interactions, their potential bleeding risk, and the way to deal with some bleeding complications. The authors conclude that the use of NOACs both in the acute phase and in the extended phase is equally effective to conventional therapy and associated with fewer major bleeding events, which make their use in patients at higher risk of recurrences safer.

Direct oral anticoagulants in patients with atrial fibrillation and renal impairment, extremes in weight, or advanced age

A growing number of patients with an indication for stroke prevention in atrial fibrillation have kidney-, age-, or weight-related alterations in pharmacokinetics that affect dosing of direct oral anticoagulants. Because these patients were excluded from or comprised a small number of patients in clinical trials, there is a lack of evidence to guide clinicians. As a consequence, many patients do not receive oral anticoagulation despite a high risk for atrial fibrillation-related stroke. Here, we present a review of direct oral anticoagulant pharmacokinetics and a review of the available clinical evidence in patients with weight-, kidney-, and age-related disease.

Does Anticoagulant Medication Alter Fracture-Healing? A Morphological and Biomechanical Evaluation of the Possible Effects of Rivaroxaban and Enoxaparin Using a Rat Closed Fracture Model

Low molecular weight heparin (LMWH) is routinely used to prevent thromboembolism in orthopaedic surgery, especially in the treatment of fractures or after joint-replacement. Impairment of fracture-healing due to increased bone-desorption, delayed remodelling and lower calcification caused by direct osteoclast stimulation is a well-known side effect of unfractioned heparin. However, the effect of LMWH is unclear and controversial. Recent studies strongly suggest impairment of bone-healing in-vitro and in animal models, characterized by a significant decrease in volume and quality of new-formed callus. Since October 2008, Rivaroxaban (Xarelto) is available for prophylactic use in elective knee- and hip-arthroplasty. Recently, some evidence has been found indicating an in vitro dose independent reduction of osteoblast function after Rivaroxaban treatment. In this study, the possible influence of Rivaroxaban and Enoxaparin on bone-healing in vivo was studied using a standardized, closed rodent fracture-model. 70 male Wistar-rats were randomized to Rivaroxaban, Enoxaparin or control groups. After pinning the right femur, a closed, transverse fracture was produced. 21 days later, the animals were sacrificed and both femora harvested. Analysis was done by biomechanical testing (three-point bending) and micro CT. Both investigated substances showed histomorphometric alterations of the newly formed callus assessed by micro CT analysis. In detail the bone (callus) volume was enhanced (sign. for Rivaroxaban) and the density reduced. The bone mineral content was enhanced accordingly (sign. for Rivaroxaban). Trabecular thickness was reduced (sign. for Rivaroxaban). Furthermore, both drugs showed significant enlarged bone (callus) surface and degree of anisotropy. In contrast, the biomechanical properties of the treated bones were equal to controls. To summarize, the morphological alterations of the fracture-callus did not result in functionally relevant deficits.

Who Were the Early Adopters of Dabigatran?: An Application of Group-based Trajectory Models

BACKGROUND

Variation in physician adoption of new medications is poorly understood. Traditional approaches (eg, measuring time to first prescription) may mask substantial heterogeneity in technology adoption.

OBJECTIVE

Apply group-based trajectory models to examine the physician adoption of dabigratran, a novel anticoagulant.

METHODS

A retrospective cohort study using prescribing data from IMS Xponent™ on all Pennsylvania physicians regularly prescribing anticoagulants (n=3911) and data on their characteristics from the American Medical Association Masterfile. We examined time to first dabigatran prescription and group-based trajectory models to identify adoption trajectories in the first 15 months. Factors associated with rapid adoption were examined using multivariate logistic regressions.

OUTCOMES

Trajectories of monthly share of oral anticoagulant prescriptions for dabigatran.

RESULTS

We identified 5 distinct adoption trajectories: 3.7% rapidly and extensively adopted dabigatran (adopting in ≤3 mo with 45% of prescriptions) and 13.4% were rapid and moderate adopters (≤3 mo with 20% share). Two groups accounting for 21.6% and 16.1% of physicians, respectively, were slower to adopt (6-10 mo post-introduction) and dabigatran accounted for <10% share. Nearly half (45.2%) of anticoagulant prescribers did not adopt dabigatran. Cardiologists were much more likely than primary care physicians to rapidly adopt [odds ratio (OR)=12.2; 95% confidence interval (CI), 9.27-16.1] as were younger prescribers (age 36-45 y: OR=1.49, 95% CI, 1.13-1.95; age 46-55: OR=1.34, 95% CI, 1.07-1.69 vs. >55 y).

CONCLUSIONS

Trajectories of physician adoption of dabigatran were highly variable with significant differences across specialties. Heterogeneity in physician adoption has potential implications for the cost and effectiveness of treatment.

Spontaneously reported haemorrhagic adverse events associated with rivaroxaban and dabigatran in Australia

OBJECTIVES

The objective of our study was to describe spontaneously reported haemorrhagic adverse events associated with rivaroxaban and dabigatran in Australia.

METHODS

Data were sourced from the Australian Therapeutic Goods Administration (TGA) Database of Adverse Event Notifications between June 2009 and May 2014. Records of haemorrhagic adverse events in which rivaroxaban or dabigatran was considered as a potential cause were analysed.

RESULTS

There were 240 haemorrhagic adverse events associated with rivaroxaban and 504 associated with dabigatran. Age was specified for 164 (68%) haemorrhages associated with rivaroxaban, of which 101 occurred in people aged ⩾75 years. Age was specified for 437 (87%) haemorrhages associated with dabigatran, of which 300 occurred in people aged ⩾75 years. Time from treatment initiation to haemorrhage was specified for 122 (51%) haemorrhages associated with rivaroxaban, with 69 (57%) haemorrhages occurring within 30 days of rivaroxaban initiation. Time from treatment initiation to haemorrhage was specified for 253 (50%) haemorrhages associated with dabigatran, with 123 (49%) haemorrhages occurring within 30 days of dabigatran initiation. Gastrointestinal (GI) haemorrhages were the most frequent type of haemorrhages associated with both rivaroxaban (n = 105, 44%) and dabigatran (n = 302, 60%). Data were available on the severity of haemorrhage for 101 (42%) haemorrhages associated with rivaroxaban, with haemorrhage leading to death in 17 people. The severity of haemorrhage was specified for 384 (76%) haemorrhages associated with dabigatran, with haemorrhage leading to death in 61 people.

CONCLUSIONS

Our study highlights the need for research on the haemorrhagic complications of anticoagulation in clinical care. A considerable proportion of reported haemorrhagic events occurred within 30 days of rivaroxaban and dabigatran initiation. This highlights the importance of considering bleeding risk at the time of treatment initiation.

Current Clinical Trials on the Use of Direct Oral Anticoagulants in the Pediatric Population

Common treatment options for deep vein thrombosis and venous thromboembolism in the pediatric population include unfractionated heparin, low molecular weight heparin, and warfarin. Other alternatives are bivalirudin, argatroban, and fondaparinux. Warfarin is the only approved oral option, but an oral agent without frequent monitoring would be optimal for pediatric patients. Thus, there is an increasing need for new anticoagulation options in this population. None of the current direct oral anticoagulants have FDA-approved indications and dosing in children. The two classes of DOACs and the drugs they are comprised of are factor Xa inhibitors (rivaroxaban, apixaban, edoxaban) and direct thrombin inhibitor (dabigatran). Off-label usage of these agents is largely based on adult doses. By far, rivaroxaban and dabigatran have the most published data and ongoing trials in pediatric patients compared to edoxaban and apixaban. After evaluating the current literature available on these agents, it is, however, still too early to make any definitive recommendations on their usage in this special population.

Recent advances in anticoagulant drug delivery

INTRODUCTION

Anticoagulants have been prescribed to patients to prevent deep vein thrombosis or pulmonary embolism. However, because of several problems in anticoagulant therapy, much attention has been directed at developing an ideal anticoagulant, and numerous attempts have been made to develop new anticoagulant delivery systems in recent years.

AREAS COVERED

This review discusses the challenges associated with the recent development of anticoagulants and their delivery systems. Various delivery methods have been developed to improve the use of anticoagulants. Recent advances in anticoagulant delivery and antidote development are also discussed in the context of their current progression states.

EXPERT OPINION

There have been many different approaches to developing the delivery system of anticoagulants. One approach has been to expand the use of new oral agents and develop their antidotes. Reducing the size of heparins to use smaller heparins for delivery, and developing oral or topical heparins are also some of the approaches used. Various physical formulations or chemical modifications are other ways that have enhanced the therapeutic potential of anticoagulant agents. On the whole, recent advances have contributed to increasing the efficacy and safety of anticoagulant clinically and have benefited the field of anticoagulant delivery.

Bleeding risks with novel oral anticoagulants during catheter ablation of atrial fibrillation: a systematic review and network meta-analysis

BACKGROUND

Comprehensive comparisons of safety (measured by bleeding risk) between multiple novel oral anticoagulants (NOACs and warfarin) in the peri-procedural period of catheter ablation (CA) for atrial fibrillation (AF) are rare.

METHODS AND RESULTS

MEDLINE, EMBASE, and COCHRANE LIBRARY were searched up to February 2015 by two reviewers independently. Predefined inclusion criteria identified 24 studies which were included in the analysis. Data were extracted by two researchers, and a network meta-analysis was conducted in R with R2WinBugS package, within Bayesian framework. Pooled odds ratios (OR) and 95% confidence intervals (CI) were summarized to evaluate the bleeding risks of three novel anticoagulants (dabigatran, rivaroxaban, apixaban) in AF patients undergoing catheter ablation (CA). With respect to total bleeding risk, no significant difference was observed between dabigatran, rivaroxaban, apixaban, and vitamin K antagonists (VKAs) by mixed-treatment comparison. The similar results were seen in the direct comparison. While dabigatran was associated with a lower rate of minor bleeding in comparison to VKAs (OR = 0.67 with 95%CI 0.49-0.93).

CONCLUSIONS

Risks of bleeding with dabigatran, rivaroxaban, apixaban, and VKAs were similar in peri-procedural period of CA for AF.

Survey of pharmacists' subtherapeutic INR management and anticoagulation bridging practices

WHAT IS KNOWN AND OBJECTIVE

Despite extensive warfarin use, optimal management of subtherapeutic international normalized ratios (INRs) remains unclear. This study assessed the differences in bridging practices among pharmacists with varying levels of experience, residency training and prescribing privileges.

METHODS

An electronic survey was distributed to two ambulatory care pharmacist e-mail lists. Respondents indicated if they would utilize parenteral anticoagulation bridging in 16 clinical scenarios at three therapeutic time points. The scenarios included patients with atrial fibrillation (AFib) (CHADS₂ score of 3-4), AFib (CHADS₂ score of 5-6) and venous thromboembolism (VTE). The AFib time points were as follows: anticoagulation initiation, early phase (<1 month) and maintenance phase (>1 month). VTE time points included early phase (<1 month), months 2-3 and maintenance phase (>3 months).

RESULTS AND DISCUSSION

The survey was completed by 143 respondents. In only three of the scenarios did >50% of respondents indicate they would utilize parenteral anticoagulation bridging. No statistically significant differences in bridging practices were identified between pharmacists providing anticoagulation services in different clinic settings. However, there were significant differences in bridging practices between pharmacists with varying levels of experience, residency training and prescribing privileges in some, but not all of the scenarios.

WHAT IS NEW AND CONCLUSION

The standards of care for subtherapeutic INRs warrant further definition.

Dabigatran adherence in atrial fibrillation patients during the first year after diagnosis: a nationwide cohort study

BACKGROUND

There is a perception among physicians that lack of routine monitoring with non-vitamin K antagonist oral anticoagulants (NOACs) may lead to poor adherence to medication. We studied adherence during the first year of usage in a cohort of patients with newly diagnosed non-valvular atrial fibrillation (AF) started on the NOAC, dabigatran etexilate.

METHODS AND RESULTS

Nationwide Danish patient and prescription purchase registries were used to identify newly diagnosed AF patients taking dabigatran, comorbidities, and refill patterns under a twice-daily, one pill regimen. Adherence was characterized among remaining users (N = 2960) after 1 year using the proportion of days covered (PDC), gap rates and restart rates. The overall 1-year PDC was 83.9%, with 76.8% of patients having a 1-year PDC in excess of 80%. Patients with a CHA2 DS2 -VASc score ≥ 2 were more adherent to medication regimes than patients with a CHA2 DS2 -VASc score of 1 (PDC ratio, 1.12; 95% confidence interval [CI], 1.08-1.17) and generally patients with higher morbidity showed more adherence. Patients with prior bleeding were not less adherent to medication regimes than patients with no prior bleeding (PDC ratio, 1.02; 95% CI, 0.98-1.06). The overall gap rate was 1.4 gaps per year. There were no clear tendencies in gap rates among subgroups, although patients with higher morbidity tended to have slightly more, but shorter, gap periods.

CONCLUSIONS

More than 75% of patients were showed > 80% adherence to medication regimes during the first year. Patients with higher morbidity, including patients with a higher risk of stroke or bleeding, exhibited better adherence. This improvement may be attributable to more regular contact with the healthcare system.

New oral anticoagulants: a practical guide on prescription, laboratory testing and peri-procedural/bleeding management. Australasian Society of Thrombosis and Haemostasis

New oral anticoagulants (NOAC) are becoming available as alternatives to warfarin to prevent systemic embolism in patients with non-valvular atrial fibrillation and for the treatment and prevention of venous thromboembolism. An in-depth understanding of their pharmacology is invaluable for appropriate prescription and optimal management of patients receiving these drugs should unexpected complications (such as bleeding) occur, or the patient requires urgent surgery. The Australasian Society of Thrombosis and Haemostasis has set out to inform physicians on the use of the different NOAC based on current available evidence focusing on: (i) selection of the most suitable patient groups to receive NOAC, (ii) laboratory measurements of NOAC in appropriate circumstances and (iii) management of patients taking NOAC in the perioperative period, and strategies to manage bleeding complications or 'reverse' the anticoagulant effects for urgent invasive procedures.