Laboratory measurement of the anticoagulant activity of edoxaban: a systematic review

Distribution of anti-factor Xa activity in patients with nonvalvular atrial fibrillation receiving 15 mg dose of edoxaban

Background

The distribution of anti-factor Xa activity (AXA) in patients with nonvalvular atrial fibrillation (NVAF) taking edoxaban 15 mg has not been fully elucidated.

Methods and Results

The trough and peak AXA were measured in 19 NVAF patients taking edoxaban 15 mg. We compared these results with those in patients taking edoxaban 30 mg. The peak AXA differed significantly between the 15 mg and the 30 mg groups (0.74 ± 0.40 IU/mL vs. 1.25 ± 0.48 IU/mL, respectively; p < 0.0001).

Conclusions

Peak but trough AXA in the patients receiving edoxaban 15 mg were significantly lower than those in patients receiving edoxaban 30 mg.

An exploratory study of effectiveness and safety of rivaroxaban in patients with left ventricular thrombus (R-DISSOLVE)

Evidence on the treatment for left ventricular (LV) thrombus is limited and mainly derives from retrospective studies. The aim of R-DISSOLVE was to explore the effectiveness and safety of rivaroxaban in patients with LV thrombus. R-DISSOLVE was a prospective, interventional, single-arm study, conducted from Oct 2020 to June 2022 at Fuwai Hospital, China. Patients with a history of LV thrombus < 3 months and with systemic anticoagulation therapy < 1 month were included. The thrombus was quantitatively confirmed by contrast-enhanced echocardiography (CE) at baseline and follow-up visits. Eligible patients were assigned to rivaroxaban (20 mg once daily or 15 mg if creatinine clearance was between 30 and 49 mL/min) and its concentration was determined by detecting anti-Xa activity. The primary efficacy outcome was the rate of LV thrombus resolution at 12 weeks. The main safety outcome was the composite of ISTH major and clinically relevant non-major bleeding. A total of 64 patients with complete CE results were analyzed for efficacy outcomes. The mean LV ejection fraction was 25.4 ± 9.0%. The dose-response curve of rivaroxaban was satisfactory based on the peak and trough plasma levels and all concentrations were in the recommended treatment range according to NOAC guidelines. The incidence rate of thrombus resolution at 6 weeks was 66.1% (41/62, 95% CI 53.0-77.7%), and of thrombus resolution or reduction was 95.2% (59/62, 95% CI 86.5-99.0%). At 12 weeks, the thrombus resolution rate was 78.1% (50/64, 95% CI 66.0-87.5%) while the rate of thrombus resolution or reduction was 95.3% (61/64, 95% CI 86.9-99.0%). The main safety outcome occurred in 4 of 75 patients (5.3%) (2 ISTH major bleeding and 2 clinically relevant non-major bleeding). In patients with LV thrombus, we reported a high thrombus resolution rate with acceptable safety by rivaroxaban, which could be a potential option for further LV thrombus treatment.Trial registration This study was registered at ClinicalTrials.gov as NCT04970381.

Anti-factor Xa activity, prothrombin time, and activated partial thromboplastin time in patients treated with factor Xa inhibitors

The regimens for factor Xa (FXa) inhibitors (apixaban, edoxaban, and rivaroxaban) vary with venous thromboembolism (VTE) or non-valvular atrial fibrillation (NVAF). The dosage and duration of FXa inhibitor therapy also differ. However, the distribution of anti-factor Xa activity (AXA) values, prothrombin time (PT), and activated partial thromboplastin time (APTT) in patients administered each FXa inhibitor has not fully been assessed. Trough and peak AXA values, PT, and APTT were measured in 85 patients taking apixaban, 105 patients taking edoxaban, and 27 patients taking rivaroxaban. The patients were further divided into three groups based on the dosage. Each FXa inhibitor showed various ranges of AXA values, and twice-daily use resulted in higher absolute AXA values than once-daily use. AXA values and PT for 20 mg apixaban at both trough and peak times were significantly higher than those for 5 mg or 10 mg. AXA values for 60 mg edoxaban at peak time were significantly higher than those for 15 mg or 30 mg. AXA values for 30 mg of rivaroxaban at both trough and peak times were significantly higher than those for 10 mg or 15 mg. In a nonlinear regression model of the relationship between AXA and PT or APTT, PT was positively correlated with AXA values for each FXa inhibitor. This study obtained trough and peak levels of AXA, PT, and APTT in patients with VTE or NVAF who were administered apixaban, edoxaban, and rivaroxaban.

Evidence-based Management of Major Bleeding in Patients Receiving Direct Oral Anticoagulants: An Updated Narrative Review on the Role of Specific Reversal Agents

The indications of direct oral anticoagulants (DOACs) have expanded over the past 15 years. DOACs are effective and safe oral anticoagulants associated with lower bleeding risks and mortality than vitamin K antagonists. However, DOAC users are prone to a considerable bleeding risk, which can occur at critical sites or lead to severe life-threatening conditions. Recent statistics indicated that major bleeding occurs in up to 6.62 DOAC users per 100 treatment years. With the increased use of DOACs in clinical practice, DOAC-associated major bleeding is expected to be encountered more frequently in the emergency department. The current international guidelines recommend specific reversal agents for the management of DOAC users with severe bleeding to reverse the anticoagulant effect and restore normal hemostasis. An individualized assessment was incorporated in specific clinical situations to guide the decision pathway of major bleeding management. However, specific reversal agents are unavailable or have limited availability in many countries, which is expected to negatively impact the clinical outcomes of DOAC-associated major bleeding. Limited real-world evidence is available from these countries regarding the clinical outcomes of patients with DOAC-associated major bleeding. This narrative review provided an updated assessment of the evidence-based approaches for the management of major bleeding in DOAC users. We also explored the clinical outcomes of patients with major bleeding from clinical settings where specific reversal agents are unavailable.

Factors Associated With Edoxaban Concentration Among Patients With Atrial Fibrillation

Background and Purpose: Edoxaban exposure varies across different ethnicities. The purpose of our study was to examine the risk factors associated with high or low edoxaban concentrations in Asian populations.

Methods: Participants with atrial fibrillation who were undergoing edoxaban therapy were enrolled. Peak (1–4 h after edoxaban administration) and trough (24 ± 4 h from the last edoxaban dose) blood samples were collected to measure edoxaban concentrations using ultrahigh-performance liquid chromatography with tandem mass spectrometry. The edoxaban concentrations were compared to those observed in clinical trials to define a higher- or lower-than-expected range. Multivariate logistic regression was used to analyze the risk factors associated with high or low edoxaban concentrations.

Results: Eighty participants (49 men, 61.3%) were enrolled and provided 78 trough and 76 peak samples. Twenty participants (25.6%) were determined to have low trough concentrations, which was associated with higher creatinine clearance and the use of the 30 mg regimen (odds ratio [OR] and 95% confidence interval [CI], 1.06 [1.01, 1.11], p = 0.01 and 5.77 [1.34, 24.75], p = 0.02, respectively). In contrast, 21 participants (27.6%) had high peak concentrations, which was associated with an off-label overdosing regimen (OR = 4.68 [1.23, 17.70], p = 0.02).

Conclusion: Our study identified factors associated with increased or decreased edoxaban exposure. The measurement of edoxaban concentration may be recommended for patients with selected characteristics.

From Activated Partial Thromboplastin Time to Antifactor Xa and Back Again

OBJECTIVES

Monitoring is essential to safe anticoagulation prescribing and requires close collaboration among pathologists, clinicians, and pharmacists.

METHODS

We describe our experience in the evolving strategy for laboratory testing of unfractionated heparin (UFH).

RESULTS

An intrainstitutional investigation revealed significant discordance between activated partial thromboplastin time (aPTT) and antifactor Xa (anti-Xa) assays, prompting a transition from the former to the latter in 2013. With the increasing use of oral factor Xa inhibitors (eg, apixaban, rivaroxaban, edoxaban, betrixaban), which interfere with the anti-Xa assay, we adapted our protocol again to incorporate aPTT in patients admitted on oral Xa inhibitors who require transition to UFH.

CONCLUSIONS

Our experience demonstrates key challenges in anticoagulation and highlights the importance of clinical pathologists in helping health systems adapt to the changing anticoagulation landscape.

Direct oral anticoagulants (DOACs) and neck of femur fractures: Standardising the perioperative management and time to surgery

Demographic projections for hip fragility fractures indicate a rising annual incidence by virtue of a multimorbid, ageing population with more noncommunicable diseases (NCDs). NCDs are characterised by slow progression and long duration ranging from ischaemic cardiovascular disease, cerebrovascular disease, diabetes, chronic obstructive pulmonary disease to various cancers. Management of this disease burden often involves commencing patients on oral anticoagulants to reduce the risk of thromboembolic events. The use of direct oral anticoagulants (DOACs) in clinical practice has increased due to their rapid onset of action, short half-life and predictable anticoagulant effects, without the need for routine monitoring. Safe and timely surgical intervention relies on reversal of anticoagulants. However, the lack of specific evidence-based guidelines for the perioperative management of patients on DOACs with hip fractures has proved challenging; in particular, the accessibility of DOAC-specific assays, justification of the cost-benefit ratio of targeted reversal agents and indications for neuraxial anaesthesia. This has led to potentially avoidable delays in surgical intervention. Following a literature review of the pharmacokinetic and pharmacodynamics of commonly used DOACs in our region including the role of surrogate markers, we propose a systematic, evidence-based guideline to the perioperative management of hip fractures DOACs. We believe this standardised protocol can be easily replicated between hospitals. We recommend that if patients are deemed suitable for a general anaesthesia, with satisfactory renal function, optimal surgical time should be 24 h following the last ingested dose of DOAC.

Pharmacokinetic-Pharmacodynamic Analysis' Role in Design of Phase ⅠClinical Trials of Anticoagulant Agents: A Systematic Review

INTRODUCTION

There remains an unmet need for better anticoagulants. The phase I clinical trial is of great significance in the development of anticoagulants, and the design is special. This system review aims to provide insights for the design of future phase I clinical trials of anticoagulants.

AREAS COVERED

We searched the database PubMed and ClinicalTrail.gov website, to collate the phase I clinical trial of anticoagulants in healthy people. The study protocol, inclusion-exclusion criteria, safety, and pharmacodynamic indexes were reviewed.

EXPERT OPINION

New anticoagulants under development focused on inhibiting one or more than one serine proteases within the coagulation cascade. Agents targeting intrinsic factors are in the pipeline of the drug development. The enrollment eligibility criteria have more restrictions on laboratory tests, medical history, or medication history related to bleeding and coagulation; more precautions were taken to assess and minimize the risk of hemorrhagic events. Pharmacodynamics markers were evaluated as a surrogate marker of anticoagulation potency to guide further dose selection in drug's development. In future, the positive control study can be applied in phase I studies of new anticoagulants with appropriate pharmacodynamics markers, which can provide more favorable information on making 'go/no' decision in drug development.

An illustrated review of bleeding assessment tools and common coagulation tests

Recognizing the complexity of coagulation tests and currently used anticoagulants, we developed this illustrated review on bleeding assessment tools and common coagulation screening tests. Quantitative bleeding assessment tools (BATs) are available to standardize the bleeding history and improve the pretest probability prior to coagulation testing. We describe use of BATs and the principles, indications, and limitations of the prothrombin time (PT)/International Normalized Ratio, activated partial thromboplastin time (APTT), and 50:50 mix. Use of these tests to identify coagulation factor deficiencies, specific and nonspecific inhibitors, coagulopathy of liver disease, disseminated intravascular coagulation, and commonly used anticoagulant medications are reviewed. Current literature suggests that unnecessary coagulation testing is rampant. The PT and APTT have astoundingly low sensitivity (1.0%-2.1%) for detection of clinically significant bleeding disorders. Thus, current guidelines recommend against the use of screening PT and APTT in preoperative patients undergoing noncardiac/vascular surgery.

Ischemic stroke and dose adjustment of oral Factor Xa inhibitors in patients with atrial fibrillation

BACKGROUND

Oral Factor Xa inhibitors for the prevention of stroke in atrial fibrillation require dose adjustment based on certain clinical criteria, but the off-label use of the reduced doses is common.

METHODS

Data from an observational registry including patients admitted with acute cerebral ischemia while taking oral Factor Xa inhibitors for atrial fibrillation between April 2016 and December 2018 were investigated. The dose regimen of the Xa inhibitor was classified as "appropriate", "underdosed" and "overdosed" in conformity with the European Medicines Agency labelling. The effect of underdosing on the functional factor Xa plasma level on admission, the clinical stroke severity and the functional outcome after 3 months were investigated.

RESULTS

254 patients with cerebral ischemia while on Factor Xa inhibitors were included. The dose regimen of the Factor Xa inhibitor was appropriate in 166 patients (65%), underdosed in 67 patients (26%) and overdosed in 21 patients (8%). Underdosing was associated with female sex, diabetes mellitus and higher CHA₂DS₂-Vasc scores. Underdosing independently predicted lower anti-Xa plasma levels on admission [median 69.4 ng/ml (IQR 0.0-121.6) vs. 129.2 ng/ml (65.5-207.2); p < 0.001], was associated with higher NIHSS scores on admission [median 5 (IQR 1-10) vs. 3 (1-7); p = 0.041] and worse functional outcome after 3 months (favorable outcome 26.9% vs. 46.9%; p = 0.025).

CONCLUSION

One in three patients with ischemic stroke during treatment with oral Xa inhibitors used inappropriate dose regimens. Underdosing was associated with lower functional plasma levels, higher clinical stroke severity and worse functional outcome.

Association between plasma concentration of edoxaban determined by direct and indirect methods in Japanese patients with non-valvular atrial fibrillation (CVI ARO 7)

Direct oral anticoagulants, including edoxaban, primarily do not need routine monitoring of the anticoagulant effect. However, extremely high/low plasma concentrations of edoxaban (PC-Ed) should be properly evaluated, especially when patients under anticoagulation therapy are at an emergency state. For this purpose, PC-Ed determined by an anti-Xa assay (indirect PC-Ed) is more convenient and, therefore, more useful compared with PC-Ed determined by an LC-MS/MS (direct PC-Ed) in daily clinical practice. Consecutive 97 patients with non-valvular atrial fibrillation (NVAF) under edoxaban therapy were evaluated, in whom edoxaban 60/30 mg doses were prescribed for 48/49 patients, 71 (73.2%) were men, and the average age was 69 years. CHADS2 score 0, 1, and ≥ 2 were 26.8%, 44.3%, and 28.9%, while CHA2DS2-VASc score 0, 1, and ≥ 2 were 14.4%, 16.5%, and 69.1%, respectively. Median values of direct and indirect PC-Ed by LC-MS/MS and anti-Xa assay were 187.1 and 176.1 ng/mL at peak (2-4 h post-dose) and 14.4 and 17.5 ng/mL at trough (pre-dose), respectively. The PC-Ed at peak and trough by two methods were significantly correlated, and the correlation coefficients were r = 0.973 and 0.963 (both, p < 0.0001), respectively. By a Bland-Altman plot, mean differences between the direct and indirect PC-Ed [lower to upper percent limit of agreement] were - 4.87 [- 46.71 to 36.98] and 4.66 [- 1.37 to 10.69] ng/mL at peak and trough, respectively. Moreover, mean % error for difference between the direct and indirect PC-Ed [lower to upper percent limit of agreement] was - 1.22 [- 20.59 to 18.14] and 31.75 [- 14.03 to 77.53] % at peak and trough, respectively, where the % error extremely increased around the lower limit of detection (LLOD) in the anti-Xa assay. Strong similarity was observed between the direct and indirect PC-Ed, especially at peak. The indirect PC-Ed was higher than the direct PC-Ed, especially around the LLOD, suggesting the need for caution when we use the anti-Xa assay for measurement of trough PC-Ed (UMIN 000032492).

An Update on the Reversal of Non-Vitamin K Antagonist Oral Anticoagulants

Non-vitamin K antagonist oral anticoagulants (NOACs) include thrombin inhibitor dabigatran and coagulation factor Xa inhibitors rivaroxaban, apixaban, edoxaban, and betrixaban. NOACs have several benefits over warfarin, including faster time to the achieve effect, rapid onset of action, fewer documented food and drug interactions, lack of need for routine INR monitoring, and improved patient satisfaction. Local hemostatic measures, supportive care, and withholding the next NOAC dose are usually sufficient to achieve hemostasis among patients presenting with minor bleeding. The administration of reversal agents should be considered in patients on NOAC's with major bleeding manifestations (life-threatening bleeding, or major uncontrolled bleeding), or those who require rapid anticoagulant reversal for an emergent surgical procedure. The Food and Drug Administration (FDA) has approved two reversal agents for NOACs: idarucizumab for dabigatran and andexanet alfa for apixaban and rivaroxaban. The American College of Cardiology (ACC), American Heart Association (AHA), and Heart Rhythm Society (HRS) have released an updated guideline for the management of patients with atrial fibrillation that provides indications for the use of these reversal agents. In addition, the final results of the ANNEXA-4 study that evaluated the efficacy and safety of andexanet alfa were recently published. Several agents are in different phases of clinical trials, and among them, ciraparantag has shown promising results. However, their higher cost and limited availability remains a concern. Here, we provide a brief review of the available reversal agents for NOACs (nonspecific and specific), recent updates on reversal strategies, lab parameters (including point-of-care tests), NOAC resumption, and agents in development.

Responses of prothrombin time and activated partial thromboplastin time to edoxaban in Japanese patients with non-valvular atrial fibrillation: characteristics of representative reagents in Japan (CVI ARO 7)

The aims of this study were to determine the distribution of plasma concentration of edoxaban (PC-Ed) with their 90% interval (on therapy range) and its correlation with anticoagulation markers in patients with non-valvular atrial fibrillation (NVAF). Consecutive 97 NVAF patients under edoxaban therapy were evaluated (60/30 mg dose, n = 48/49; men/women, n = 71/26; age, 69 years). CHADS2 score 0, 1, and ≥ 2 were 27%, 44%, and 29%, respectively. The mean (90% interval) of PC-Ed by LC-MS/MS was 194.3 (49.4-345.3) and 17.0 (4.8-40.7) ng/mL at peak (2-4 h post-dose) and trough (pre-dose), respectively. Correlation of prothrombin time (PT) with PC-Ed was higher than that of activated partial thromboplastin time (aPTT). Among 6 PT reagents, Coagupia PT-N and Simplastin Excel S (both PT reagents) showed the highest predictive capability for the upper outlier of PC-Ed at peak and trough. Among 4 aPTT reagents, only Thrombocheck APTT measured at peak had a significant predictive capability. When using PT reagents, both peak and trough sampling showed a similar predictive capability for the upper outliers of PC-Ed with a high sensitivity, but a relatively low specificity. We demonstrated the distributions of plasma concentration, PT with 6 reagents, and aPTT with 4 reagents under edoxaban therapy in Japanese patients with NVAF, showing their 90% intervals. For predicting the upper outlier of PC-Ed, PT was more sensitive compared with aPTT, whereas predicting capability for the outliers of PC-Ed was mostly similar between peak and trough samplings among PT reagents (UMIN 000032492).

The 2018 European Heart Rhythm Association Practical Guide on the use of non-vitamin K antagonist oral anticoagulants in patients with atrial fibrillation

The current manuscript is the second update of the original Practical Guide, published in 2013 [Heidbuchel et al. European Heart Rhythm Association Practical Guide on the use of new oral anticoagulants in patients with non-valvular atrial fibrillation. Europace 2013;15:625-651; Heidbuchel et al. Updated European Heart Rhythm Association Practical Guide on the use of non-vitamin K antagonist anticoagulants in patients with non-valvular atrial fibrillation. Europace 2015;17:1467-1507]. Non-vitamin K antagonist oral anticoagulants (NOACs) are an alternative for vitamin K antagonists (VKAs) to prevent stroke in patients with atrial fibrillation (AF) and have emerged as the preferred choice, particularly in patients newly started on anticoagulation. Both physicians and patients are becoming more accustomed to the use of these drugs in clinical practice. However, many unresolved questions on how to optimally use these agents in specific clinical situations remain. The European Heart Rhythm Association (EHRA) set out to coordinate a unified way of informing physicians on the use of the different NOACs. A writing group identified 20 topics of concrete clinical scenarios for which practical answers were formulated, based on available evidence. The 20 topics are as follows i.e., (1) Eligibility for NOACs; (2) Practical start-up and follow-up scheme for patients on NOACs; (3) Ensuring adherence to prescribed oral anticoagulant intake; (4) Switching between anticoagulant regimens; (5) Pharmacokinetics and drug-drug interactions of NOACs; (6) NOACs in patients with chronic kidney or advanced liver disease; (7) How to measure the anticoagulant effect of NOACs; (8) NOAC plasma level measurement: rare indications, precautions, and potential pitfalls; (9) How to deal with dosing errors; (10) What to do if there is a (suspected) overdose without bleeding, or a clotting test is indicating a potential risk of bleeding; (11) Management of bleeding under NOAC therapy; (12) Patients undergoing a planned invasive procedure, surgery or ablation; (13) Patients requiring an urgent surgical intervention; (14) Patients with AF and coronary artery disease; (15) Avoiding confusion with NOAC dosing across indications; (16) Cardioversion in a NOAC-treated patient; (17) AF patients presenting with acute stroke while on NOACs; (18) NOACs in special situations; (19) Anticoagulation in AF patients with a malignancy; and (20) Optimizing dose adjustments of VKA. Additional information and downloads of the text and anticoagulation cards in different languages can be found on an EHRA website (www.NOACforAF.eu).

Periprocedural Anticoagulation Management For Nonoperating Room Anesthesia Procedures: A Clinical Guide

Non-operating room anesthesia presents unique challenges for anesthesiologists. Limited preprocedural optimization and unfamiliarity with the location and procedure itself add to the difficulties in delivering safe care for these patients. Management of chronic oral anticoagulation can prove especially problematic since risks of bleeding for non-operating room procedures vary widely and differ from traditional surgeries. In addition, many physicians may not be familiar with the growing number of newly approved oral anticoagulants and their periprocedural management. This review will examine common non-operating procedures, their risks of bleeding, as well as pharmacokinetics of oral anticoagulants available on the market and periprocedural management options.

Emergency Reversal of Anticoagulation

Owing to the propensity of anticoagulated patients to bleed, a strategy for reversal of anticoagulation induced by any of the common agents is essential. Many patients are anticoagulated with a variety of agents, including warfarin, low molecular weight heparin, and the direct oral anticoagulants such as factor Xa and factor IIa inhibitors. Patients may also be using antiplatelet agents. Recommendations to reverse bleeding in these patients are constantly evolving with the recent development of specific reversal agents. A working knowledge of hemostasis and the reversal of anticoagulation and antiplatelet drugs is required for every emergency department provider. This article reviews these topics and presents the currently recommended strategies for dealing with bleeding in the anticoagulated patient.

Comparative Effectiveness and Safety of Rivaroxaban in Adults With Nonvalvular Atrial Fibrillation

BACKGROUND

All evidence regarding benefits and harms of rivaroxaban for stroke prevention has not been appraised yet.

STUDY QUESTION

What are the comparative effectiveness and safety of rivaroxaban in adults with nonvalvular atrial fibrillation?

DATA SOURCES

Randomized controlled trials (RCTs), meta-analyses, and observational studies were identified in several databases in October 2018.

STUDY DESIGN

Rapid review with evidence appraisal using the Grading of Recommendations Assessment, Development and Evaluation working group approach.

RESULTS

Two direct RCTs (23,021 patients) suggest that rivaroxaban is noninferior to warfarin in the prevention of stroke and systemic embolism (pooled relative risk [RR] 0.73, 95% confidence interval [CI], 0.43-1.24), reduces risk of hemorrhagic stroke (RR 0.59, 95% CI, 0.38-0.92), fatal bleeding (RR 0.49, 95% CI, 0.31-0.76), and cardiac arrest (RR 0.45, 95% CI, 0.25-0.82, 2 RCTs), but increases risk of major gastrointestinal bleeding (RR 1.46, 95% CI, 1.19-1.78). In observational studies, rivaroxaban is associated with lower risk of ischemic stroke (RR 0.87, 95% CI, 0.77-0.99, 222,750 patients), acute myocardial infarction (RR 0.61, 95% CI, 0.48-0.78, 73,739 patients), and intracranial hemorrhage (RR 0.64, 95% CI, 0.45-0.92, 197,506 patients) but higher risk of gastrointestinal bleeding (RR 1.30, 95% CI, 1.19-1.42, 188,968 patients) and higher risk of mortality when compared with warfarin in European studies (RR 1.19, 103,270 patients in the UK; RR 2.02, 22,358 patients in Denmark) but lower risk of mortality in Taiwan (RR 0.58, 40,000 patients). Network meta-analyses and observational studies suggest that rivaroxaban is associated with higher risk of bleeding when compared with apixaban (RR 2.14, 72,586 patients), dabigatran (RR 1.24, 67,102 patients), and edoxaban (RR 1.32, 71,683 patients).

CONCLUSIONS

Research on the long-term comparative effectiveness, safety, and effects on quality of life between rivaroxaban and other novel oral anticoagulants is urgently needed.

Comparative Clinical Outcomes of Edoxaban in Adults With Nonvalvular Atrial Fibrillation

BACKGROUND

A critical appraisal of all pooled evidence regarding novel oral anticoagulants (NOACs) for stroke prevention regardless of publication status or study design has not been conducted yet. Being the latest addition to NOACs, the data on edoxaban are especially scarce.

STUDY QUESTION

What are the comparative clinical outcomes of edoxaban versus warfarin and other NOACs apixaban, dabigatran, or rivaroxaban in adults with nonvalvular atrial fibrillation?

DATA SOURCES

Randomized controlled trials (RCTs), observational studies, and network meta-analyses were identified in PubMed, EMBASE, the Cochrane Library, Pharmapendium, Elsevier Clinical Pharmacology, and the clinicaltrials.gov trial registry in June 2018.

STUDY DESIGN

Rapid review per a priori developed protocol, direct frequentist random-effects meta-analysis of aggregate data, grading the quality of evidence per the Grading of Recommendations Assessment, Development and Evaluation working group approach.

RESULTS

Direct 4 RCTs (23,021 patients) suggest that edoxaban is noninferior to warfarin in prevention of stroke and systemic embolism [pooled relative risk (RR): 0.65, 95% confidence interval (CI): 0.23-1.81, 2 RCTs] and reduces the risk of cardiovascular mortality (RR: 0.87, 95% CI: 0.78-0.97, 1 RCT), major cardiovascular morbidity (RR: 0.90, 95% CI: 0.82-0.98, 2 RCTs), and major bleeding events (RR: 0.80, 95% CI: 0.71-0.91, 1 RCT) but increases the risk of gastrointestinal bleeding (RR: 1.21, 95% CI: 1.01-1.46, 1 RCT) and anemia (RR: 1.45, 95% CI: 1.05-1.99, 3 RCTs). Edoxaban is superior to warfarin in patients with increased risk of bleeding with warfarin because of variants in CYP2C9 and VKORC1 genes. Indirect evidence does not allow valid conclusions regarding comparative superiority of NOACs. The quality of evidence was downgraded because of reporting bias, small number of events, and indirectness in comparisons.

CONCLUSIONS

Edoxaban is a welcome addition to the NOAC's armamentarium. However, the comparative data with other novel NOACs are mostly nonexisting, and urgently needed for better individual patient assessment.

Non-Vitamin K Oral Anticoagulants Associated Bleeding and Its Antidotes

Oral anticoagulant-associated intracerebral hemorrhage (OAC-ICH) accounts for nearly 20% of all ICH. The number of patients with an indication for oral anticoagulant therapy (OAT) increases with increasing age. OAT became less complicate with the introduction of non-vitamin K oral anticoagulants (NOAC) OAT because of easier handling, favorable risk-benefit profile, reduced rates of ICH compared to vitamin K antagonists and no need for routine coagulation testing. Consequently, despite a better safety profile of NOAC the number of patients with OAC-ICH will increase. The mortality and complication rates of OAC-ICH are high and therefore they are the most feared complication of OAT. Immediate normalization of coagulation is the main goal and therefore knowledge of pharmacodynamics and coagulation status is essential. Laboratory measurements of anticoagulant activity in NOAC patients is challenging as specific tests are not widely available. More accessible tests such as the prothrombin time and activated partial thromboplastin time have important limitations. In dabigatran-associated ICH 5 g Idarucizumab should be administered. In rivaroxaban and apixaban-associated ICHs administration of andexanet alpha should be considered. Prothrombin complex concentrate may be considered if andexanet alpha is not available or in case of an ICH associated with edoxaban.

Pharmacogenetics of novel oral anticoagulants: a review of identified gene variants & future perspectives

Novel oral anticoagulants (NOACs) are becoming a therapy of choice in everyday clinical practice after almost 50 years during which warfarin and related coumarin derivatives were used as the main anticoagulants. Advantages of NOACs over standard anticoagulants include their predictable pharmacodynamics and pharmacokinetics, stable plasma concentrations and less drug-drug and food-drug interactions. However, pharmacogenetics has its place in administration of NOACs, as considerable interindividual variations have been detected. In this review, previous findings in pharmacogenetics of dabigatran, rivaroxaban, apixaban and edoxaban are summarized, along with recommendations for studying genes encoding metabolically important enzymes for four selected NOACs. Future directions include identification of clinically relevant SNPs, and change in optimum dosage for patients who are carriers of significant variants.

The potential for evaluating the effects of intensified antithrombotic therapy using retinal optical coherence tomography angiography

Oral anticoagulants are widely used in the treatment and prevention of both venous and arterial thromboembolism. They are classified into vitamin K anticoagulants (VKAs) and non-vitamin K antagonist oral anticoagulants (NOACs). The main advantage of NOACs over VKAs is the absence of the need for continuous monitoring. However, there are concerns about their effectiveness and safety in certain clinical situations. In this manuscript, I discussed the possibility of using optical coherence tomography angiography [OCTA] in the monitoring of the activity of NOACs. The rapid development of OCTA technology is very promising. Further research and development will extend its use beyond the realm of ophthalmology.

Intravenous thrombolysis for acute ischaemic stroke in patients on direct oral anticoagulants

BACKGROUND AND PURPOSE

Whereas intravenous thrombolysis (IVT) is allowed for acute ischaemic stroke in patients on vitamin K antagonists with international normalized ratio ≤1.7, there are no similar recommendations for patients on direct oral anticoagulants (DOACs), notably due to the lack of coagulation tests to assess the therapeutic effects. Although the literature is scarce, consisting of small case series and retrospective studies, considering the frequency of this situation the French Vascular Neurology Society and the French Study Group on Haemostasis and Thrombosis have worked on a joint position paper to provide a practical position regarding the emergency management of ischaemic stroke in patients on DOACs.

METHOD

Based on a review of the literature, the authors wrote a first text that was submitted to a broad panel of members from the two societies. The text was then amended by the authors to address experts' comments and to reach a consensus.

RESULTS

In patients with normal renal function and who stopped the DOAC for at least 48 h, the management should not differ from that in patients without oral anticoagulant. In patients who are still on DOACs, mechanical thrombectomy is encouraged preferentially when applicable in first line. Otherwise, when specific tests are available, values <50 ng/ml indicate that IVT is allowed. In the absence of specific tests, standard tests (thrombin time, prothrombin time and activated partial thromboplastin time) can be used for dabigatran and rivaroxaban, although interpretation of these tests may be less reliable. In some patients on dabigatran, idarucizumab may be used before IVT.

CONCLUSIONS

In this expert opinion paper, it is suggested that IVT can be performed in patients selected according to the time elapsed since the drug was last taken, renal function, type of hospital where the patient is admitted and plasma concentration of DOAC.

Pharmacologic Reversal of Direct Oral Anticoagulants

Direct oral anticoagulants are becoming increasingly popular in outpatient use. These medications have lacked specific reversal agents. However, this is changing. The Federal Food and Drug Administration approved idarucizumab for reversal of dabigatran in 2016, and another agent, andexanet alfa, is currently in clinical trials for reversal of rivaroxaban and apixaban. This article examines the efficacy and safety of these emerging reversal agents, as well as other historical agents for reversal of direct oral anticoagulants.

Managing transitions from oral factor Xa inhibitors to unfractionated heparin infusions

PURPOSE

Published evidence regarding the effects of oral factor Xa inhibitors on anticoagulation monitoring tests is reviewed with a focus on monitoring concerns that can arise during transitions to i.v. heparin therapy.

SUMMARY

Assays that measure inhibition of factor Xa activity (i.e., anti-Xa assays) are widely used in U.S. institutions to monitor i.v. heparin therapy and, in some cases, for monitoring other types of anticoagulation therapy. Clinicians have raised concerns that the use of anti-Xa assays to monitor heparin levels in hospitalized patients who must be transitioned from oral factor Xa inhibitor therapy to i.v. unfractionated heparin (UFH) infusions could yield unquantifiable or inaccurate results, leading to unnecessary UFH dose reductions and potential treatment failures; the manufacturer labeling of oral factor Xa inhibitors (apixaban, edoxaban, and rivaroxaban) does not provide specific guidance on this issue. Results of a literature review indicated that residual effects of oral factor Xa inhibitor use can result in substantial interference with the currently available chromogenic anti-Xa assays but negligible to moderate effects on global coagulation assays, which measure activated partial thromboplastin time (aPTT) or prothrombin time. Therefore, during the transition from an oral factor Xa inhibitor to i.v. UFH therapy, it may be prudent to consider an aPTT assay for anticoagulation monitoring.

CONCLUSION

The use of oral factor Xa inhibitors appears to affect the accuracy of anti-Xa assay results, with results of global coagulation assays affected to a lesser degree.

Comparison of Anticoagulant Therapy for Atrial Fibrillation - Novel Oral Anticoagulants Versus Vitamin K Antagonists

In patients with non-valvular atrial fibrillation (NVAF), oral anticoagulation is important for prevention of stroke and systemic embolism (SE). While Vitamin K antagonists (VKAs) have historically been the standard of care, these medications are limited by numerous food and drug interactions with onerous requirements for frequent monitoring and dose adjustments. Over the past decade, several novel oral anticoagulants (NOACs) have been developed to directly inhibit factor IIa/thrombin (dabigatran) or activated factor X (apixaban, rivaroxaban, edoxaban). These medications have been shown to be at least as effective as warfarin for stroke prevention in NVAF with more favorable safety profiles. However, their advantages are underscored by a lack of specific antidotes and assays quantifying their anticoagulant effects. This paper addresses the use of NOACs compared to VKAs in patients with NVAF, with a special focus on high-risk populations, including the elderly, those with renal disease, diabetes mellitus, coronary artery disease, and previous stroke. The current literature surrounding special clinical scenarios including the treatment of bleeding, perioperative management, and the use of NOACs in cardioversion and catheter ablation will be also discussed.

Practical guidance on the use of laboratory testing in the management of bleeding in patients receiving direct oral anticoagulants

Direct oral anticoagulants (DOACs) have demonstrated a favorable benefit–risk profile in several thromboembolic disorders and are increasingly used in routine clinical practice. A number of real-world studies on DOACs are ongoing, and data published so far have shown broadly similar outcomes to those demonstrated in the respective phase III trials. Despite their beneficial attributes, bleeding risk (as with any other anticoagulants) is often a concern for physicians when prescribing DOACs, particularly in elderly patients, those with significant comorbidities, and other high-risk patient populations. Although the absence of routine coagulation monitoring is an advantage of the DOACs, measuring their anticoagulant effect and/or plasma drug levels may be helpful in certain clinical scenarios to help patient management and improve outcomes. In this paper, practical guidance and recommendations are provided for clinical situations in which the test results may aid clinical decision-making, including patients with life-threatening bleeding events, patients without bleeding but with test results indicating a risk of bleeding, for those patients with a suspected thromboembolism while receiving a DOAC, or prior to patients undergoing elective or urgent surgical procedures. Finally, appropriate monitoring of the DOACs could be of substantial benefit to patients, and there is a high potential for development in this area in the future.

Edoxaban: Impact on routine and specific coagulation assays

Assessment of plasma concentration/effect of edoxaban may be useful in some situations. Also, clinicians need to know how routine coagulation assays are influenced. It was our aim to determine coagulation tests useful for the assessment of edoxaban’s pharmacodynamics and provide recommendations for the interpretation of haemostasis diagnostic tests. Edoxaban was spiked at concentrations ranging from 0 to 1,000 ng/ml in platelet-poor plasma which covers the on-therapy range (from ± 25 ng/ml at Ctrough to ± 170 ng/ml at Cmax). aPTT, PT, dRVVT, chromogenic anti-Xa assays, TGA and a large panel of haemostasis diagnostic tests were performed using several reagents. A concentration-dependent prolongation of aPTT, PT and dRVVT was observed. The effect was dependent on the reagents. FXa chromogenic assays showed high sensitivity and a linear correlation depending on the methodology. TGA may be useful to assess the pharmacodynamics of edoxaban but its turnaround time and the lack of standardisation are limitations. Edoxaban impairs the assessment of lupus anticoagulant, protein S (clotting method), APC-R, antithrombin (FXa-based assay) and measurement of clotting factor activity. Immunological assays and assays acting below the FXa are not influenced by edoxaban. In conclusion, some PT reagents could be used to estimate edoxaban activity. Chromogenic anti-Xa assays are required to assess the plasma concentration. TGA may be useful but requires standardisation. In case of thrombophilia or in the exploration of a haemorrhagic event, immunological assays should be recommended, when applicable. Standardisation of the time between the last intake and the sampling is mandatory to provide a proper assessment of the result.

Supplementary Material to this article is available online at www.thrombosis-online.com.

Determination of edoxaban equivalent concentrations in human plasma by an automated anti-factor Xa chromogenic assay

INTRODUCTION

This phase I, open-label, multiple-dose, two-treatment study assessed the relationship between edoxaban equivalent concentration derived from an anti-FXa assay with the summed concentration of edoxaban and its active metabolite, M-4, as assessed by liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS). This study also assessed the relationship between edoxaban plasma concentrations assessed by LC/MS/MS in sodium citrate and lithium heparin tubes.

MATERIALS AND METHODS

Healthy volunteers were randomized to receive once-daily edoxaban 60mg or 90mg for 5days (15 participants per treatment group). Serial blood samples were collected for analysis by LC/MS/MS and by the anti-FXa assay. Edoxaban equivalent levels were assessed using a commercially available anti-FXa activity assay with an edoxaban-specific setup.

RESULTS AND CONCLUSIONS

The day 5 concentration estimates were significantly correlated between the 2 assays (P<0.0001 for both edoxaban doses). The geometric least squares mean (GLSM) ratio (90% confidence interval) for edoxaban equivalent concentrations vs edoxaban + M-4 concentrations was 114.3% (108.2-120.8) for edoxaban 60mg (P<0.0001) and 113.0% (107.1-119.2) for edoxaban 90mg (P=0.0002). The GLSM ratio for edoxaban concentrations in sodium citrate vs lithium heparin tubes for 60-mg and 90-mg edoxaban doses were 82.8% (78.5-87.3) and 83.9% (79.1-89.0), respectively. In this study, an anti-FXa chromogenic assay with edoxaban-specific calibrators and controls demonstrated good accuracy in estimating edoxaban concentrations across a wide range of concentrations relative to LC/MS/MS at steady state following the administration of once-daily edoxaban for 5days.

Novel Anticoagulant Agents in the Perioperative Setting

An increasing number of oral anticoagulants have become available over the past decade. Each of these agents has differing implications on both regional and neuraxial anesthetic techniques. This article describes the pharmacology, pharmacokinetics, and pharmacodynamics of the most commonly used novel oral anticoagulants (NOACs). It also outlines recent guidelines for the use of NOACs in the perioperative setting, especially with regard to neuraxial anesthesia.

Italian intersociety consensus on DOAC use in internal medicine

The direct oral anticoagulants (DOACs) are drugs used in clinical practice since 2009 for the prevention of stroke or systemic embolism in non-valvular atrial fibrillation, and for the treatment and secondary prevention of venous thromboembolism. The four DOACs, including the three factor Xa inhibitors (rivaroxaban, apixaban and edoxaban) and one direct thrombin inhibitor (dabigatran) provide oral anticoagulation therapy alternatives to Vitamin K antagonists (VKAs). Despite their clear advantages, the DOACs require on the part of the internist a thorough knowledge of their pharmacokinetic and pharmacodynamic characteristics to ensure their correct use, laboratory monitoring and the appropriate management of adverse events. This document represents a consensus paper on the use of DOACs by representatives of three Italian scientific societies: the Italian Society of Internal Medicine (SIMI), the Federation of the Associations of Hospital Managers (FADOI), and the Society for the Study of Haemostasis and Thrombosis (SISET). This document formulates expert opinion guidance for pragmatic managing, monitoring and reversing the anticoagulant effect of DOACs in both chronic and emergency settings. This practical guidance may help the internist to create adequate protocols for patients hospitalized ion internal medicine wards, where patients are often elderly subjects affected by poly-morbidities and renal insufficiency, and, thus, require particular attention to drug-drug interactions and peri-procedural protocols.

Optimal Reversal of Novel Anticoagulants in Trauma

The incidence of patients with trauma on novel oral anticoagulants (NOACs) for the treatment of thromboembolic disorders is increasing. In severe bleeding or hemorrhage into critical spaces, urgent reversal of this underlying pharmacologic coagulopathy becomes paramount. Optimal reversal strategy for commonly used NOACs is still evolving. Basic tenets of evaluation of patients with trauma and resuscitation remain the same. Clinical outcomes data in bleeding human patients with trauma are lacking, but are needed to establish efficacy and safety in these treatments. This article summarizes the available evidence and provides the optimal reversal strategy for bleeding patients with trauma on NOACs.

Current knowledge on assessing the effects of and managing bleeding and urgent procedures with direct oral anticoagulants

PURPOSE

Current knowledge on managing major bleeding events with available hemostatic agents, including their combined use with potential reversal agents, in patients taking direct oral anticoagulant (DOACs) is reviewed.

SUMMARY

Over the past five years, a new generation of oral agents, the DOACs, has emerged as commonly used anticoagulants for stroke prevention in non-valvular atrial fibrillation, and treatment or secondary prevention of venous thromboembolism. Management of a bleeding event in the setting of DOAC therapy should take into account the relative risks of bleeding and thrombosis, which will determine the degree of anticoagulant reversal required. In the setting of a major (critical) bleeding event associated with notable blood loss, management may include transfusions of blood products to sustain the function of organ systems, and the availability of specific reversal agents will provide additional options for bleeding management. Beyond withholding the DOAC and providing supportive management that addresses any factors contributing to the bleeding event, clinicians may desire to expedite the removal of any anticoagulation effects. In general, this is accomplished by either removing or neutralizing the anticoagulant or by independently establishing hemostasis.

CONCLUSION

With or without reversal agents, patients may require supportive management such as mechanical pressure, volume support, transfusions of blood products, and, depending on the situation, surgery to repair the bleeding source. Specific reversal agents are currently under development or have recently been approved for the urgent management of bleeding events or the facilitation of invasive procedures in patients receiving DOACs.