Reversal of antithrombotic agents

Role of Thrombosis in Neurodegenerative Diseases: An Intricate Mechanism of Neurovascular Complications

Thrombosis, the formation of blood clots in arteries or veins, poses a significant health risk by disrupting the blood flow. It can potentially lead to major cardiovascular complications such as acute myocardial infarction or ischemic stroke (arterial thrombosis) and deep vein thrombosis or pulmonary embolism (venous thrombosis). Nevertheless, over the course of several decades, researchers have observed an association between different cardiovascular events and neurodegenerative diseases, which progressively harm and impair parts of the nervous system, particularly the brain. Furthermore, thrombotic complications have been identified in numerous clinical instances of neurodegenerative diseases, particularly Alzheimer's disease, Parkinson's disease, multiple sclerosis, and Huntington's disease. Substantial research indicates that endothelial dysfunction, vascular inflammation, coagulation abnormalities, and platelet hyperactivation are commonly observed in these conditions, collectively contributing to an increased risk of thrombosis. Thrombosis can, in turn, contribute to the onset, pathogenesis, and severity of these neurological disorders. Hence, this concise review comprehensively explores the correlation between cardiovascular diseases and neurodegenerative diseases, elucidating the cellular and molecular mechanisms of thrombosis in these neurodegenerative diseases. Additionally, a detailed discussion is provided on the commonly employed antithrombotic medications in the context of these neuronal diseases.

Reversal strategies and outcomes in patients with atrial fibrillation and warfarin-associated intracranial hemorrhage

PURPOSE

Evaluate reversal strategies in atrial fibrillation (AF) patients with warfarin-associated intracranial hemorrhage (ICH) in clinical care.

MATERIALS AND METHODS

Observational cohort of AF patients with warfarin-associated ICH at two referral hospitals (2007-2010), with patient features, reversal agents, and outcomes collected from medical records.

RESULTS

Among 498 ICH patients 403 received fresh frozen plasma (FFP) without 3-factor prothrombin complex concentrates (PCCs) or recombinant factor VIIa (rFVIIa), 65 received PCCs or rFVIIa, mostly with FFP, and 30 received no acute reversal agents. Median time from presentation to reversal agent administration was 3.4 h (IQR 2.3-5.3). INR was reversed to ≤1.4 by 6 h post-presentation in 46% of patients receiving PCCs/rFVIIa versus 15% receiving FFP alone (p<0.0001). Among PCCs/rFVIIa recipients, 31% died in-hospital vs. 24% receiving FFP alone (p=0.27). Adjusted OR for death accounting for age and Glasgow Coma Score was 0.78 (0.36-1.69) for PCCs/rFVIIa vs FFP only and 1.16 (0.59-2.27) comparing those reaching vs. not reaching INR ≤ 1.4 at 6 h.

CONCLUSIONS

Treatment with PCCs/rFVIIa led to faster INR reversal than treatment with FFP alone. Neither treatment with PCCs/rFVIIa nor rapid INR reversal was associated with improved survival. Delays receiving PCCs may largely eliminate the benefit of treatment.

A randomised study in healthy volunteers to investigate the safety, tolerability and pharmacokinetics of idarucizumab, a specific antidote to dabigatran

Idarucizumab, a monoclonal antibody fragment that binds dabigatran with high affinity, is in development as a specific antidote for dabigatran. In this first-in-human, single-rising-dose study, we investigated the pharmacokinetics, safety and tolerability of idarucizumab. Healthy male volunteers aged 18–45 years received between 20 mg and 8 g idarucizumab as a 1-hour intravenous infusion in 10 sequential dose groups, or 1, 2 or 4 g idarucizumab as a 5-minute infusion. Subjects within each dose group were randomised 3:1 to idarucizumab or placebo. A total of 110 randomised subjects received study drug (27 placebo, 83 idarucizumab). Peak and total exposure to idarucizumab increased proportionally with dose. Maximum plasma concentrations were achieved near the end of infusion, followed by a rapid decline, with an initial idarucizumab half-life of ∼45 minutes. For the 5-minute infusions, this resulted in a reduction of plasma concentrations to less than 5 % of peak within 4 hours. Idarucizumab (in the absence of dabigatran) had no effect on coagulation parameters or endogenous thrombin potential. Overall adverse event (AE) frequency was similar for idarucizumab and placebo, and no relationship with idarucizumab dose was observed. Drug-related AEs (primary endpoint) were rare (occurring in 2 placebo and 3 idarucizumab subjects) and were mostly of mild intensity; none of them resulted in study discontinuation. In conclusion, the pharmacokinetic profile of idarucizumab meets the requirement for rapid peak exposure and rapid elimination, with no effect on pharmacodynamic parameters. Idarucizumab was safe and well tolerated in healthy males.

Clinical trial registration: http://clinicaltrials.gov/ct2/show/NCT01688830?term=NCT01688830&rank=1 (NCT01688830).

Antithrombotic Reversal Agents

The actively bleeding anticoagulated patient presenting to the emergency department requires rapid evaluation and treatment, which is made increasingly complicated by the ever-evolving antithrombotic treatment options used in medicine. Even with excellent supportive care, the timeliness with which reversal decisions need to be made continues to demand of the emergency practitioner a familiarity with the properties and general characteristics of a variety of antithrombotic agents. Reversal options vary and may include vitamin K, FFP, PCC, rFVIIa, platelets, and desmopressin, among others.

Stroke Prevention in Atrial Fibrillation: A Clinical Perspective on Trials of the Novel Oral Anticoagulants

Atrial fibrillation (AF) is a common heart rhythm disturbance; its incidence increases with age, and it is also an independent risk factor for stroke. Anticoagulation has been proven as the most effective way to reduce the risk of stroke in patients with AF, and vitamin K antagonists have been used for decades as the gold standard treatment. Vitamin K antagonists have a narrow therapeutic window in addition to variable pharmacokinetics and pharmacodynamics, and they frequently interact with food and other drugs, requiring coagulation monitoring to ensure balance between safety and efficacy. The novel oral anticoagulants (NOACs) dabigatran, rivaroxaban, apixaban, and edoxaban selectively target either thrombin or Factor Xa and have predictable pharmacologic profiles, removing the need for routine coagulation monitoring. This article summarizes phase III data in patient subtypes and discusses controversies surrounding AF management with these agents. Results indicate that NOACs in non-valvular AF have an overall improved efficacy-safety profile compared with warfarin. Significantly fewer fatal bleeding events were observed in patients randomized to rivaroxaban, apixaban, or edoxaban compared with those on warfarin, and significant reductions in the incidence of life-threatening bleeding were observed in patients randomized to dabigatran. All four pivotal trials testing the NOACs against warfarin showed significantly lower rates of intracranial bleeding in patients administered NOACs. These results suggest that wider use of NOACs has the potential to improve outcomes for most patients with AF.

An Observational Study of the Factor Xa Inhibitors Rivaroxaban and Apixaban as Reported to Eight Poison Centers

STUDY OBJECTIVE

Rivaroxaban and apixaban are part of a new group of oral anticoagulants targeting factor Xa and approved by the Food and Drug Administration in 2011 and 2012. These oral anticoagulants are administered at fixed daily doses, without the need for laboratory-guided adjustments. There are limited data available on supratherapeutic doses or overdose of the oral Xa inhibitors. This study characterizes the clinical effect in patients exposed to rivaroxaban and apixaban.

METHODS

A retrospective study collected data from 8 regional poison centers covering 9 states. Cases were initially identified by a search of the poison centers' databases for case mentions involving a human exposure to Xarelto, rivaroxaban, Eliquis, or apixaban. Inclusion criteria included single-substance exposure. Exclusion criteria were animal exposure, polysubstance exposure, or information call. Data for the study were collected by individual chart review, including case narratives, and compiled into a single data set.

RESULTS

There were 223 patients: 124 (56%) were female patients, mean age was 60 years, and 20 were children younger than 12 years (9%). One hundred ninety-eight patients ingested rivaroxaban (89%) and 25 ingested apixaban (11%). Dose was reported in 182 rivaroxaban patients, with a mean dose of 64.5 mg (range 15 to 1,200 mg), and in 21 apixaban patients, with a mean dose of 9.6 mg (range 2.5 to 20 mg). For rivaroxaban, prothrombin time was measured in 49 patients (25%) and elevated in 7; partial thromboplastin time, measured in 49 (25%) and elevated in 5; and international normalized ratio, measured in 61 (31%) and elevated in 13. For apixaban, prothrombin time was measured in 6 patients (24%) and elevated in none; partial thromboplastin time, measure in 6 (24%) and elevated in none; and international normalized ratio, measured in 5 patients (20%) and elevated in none. Bleeding was reported in 15 patients (7%): 11 rivaroxaban and 4 apixaban. The site of bleeding was gastrointestinal (8), oral (2), nose (1), bruising (1), urine (1), and subdural (1). The subdural bleeding occurred after fall and head injury. All cases with bleeding involved long-term ingestions. Coagulation test results were normal in most patients with bleeding: prothrombin time 5 of 6 (83%), partial thromboplastin time 5 of 6 (83%), and international normalized ratio 5 of 9 (55%). Blood products were used in 7 rivaroxaban patients (1 suicide) and 3 apixaban patients. No bleeding or altered coagulation test results occurred in children, which all involved a one-time ingestion. All 12 suicide attempts involved rivaroxaban: altered coagulation test results occurred for 5 patients (42%), no bleeding occurred in any suicide attempt patient, 1 patient was treated with fresh frozen plasma (international normalized ratio 12.47), and dose by patient history did not predict risk of altered coagulation or bleeding. Two rivaroxaban patients experienced elevation of hepatic transaminase levels greater than 1,000 U/L.

CONCLUSION

Bleeding after Xa inhibitor ingestion as a single agent is uncommon. Prothrombin time, partial thromboplastin time, or international normalized ratio may be elevated in a minority of cases but appears unreliable to measure risk of bleeding. Massive acute ingestion in suicide attempt may result in significant anticoagulation. Single exploratory ingestion by children was not associated with toxicity.

Rivaroxaban for the treatment and prevention of thromboembolic disease

Objectives

A number of direct oral anticoagulants are now available and offer alternative strategies for anticoagulation therapy. Rivaroxaban, a direct oral Factor Xa inhibitor, is approved for use across several thromboembolic indications. This article aims to provide an overview of the key pharmacological characteristics of rivaroxaban and the rationale and evidence for the use of different dose regimens across its licenced indications, and offer practical guidance to healthcare professionals on responsible use. References were sourced via PubMed searches using the search string (rivaroxaban AND (pharmacokinetics OR pharmacodynamics OR (clinical studies) OR (drug interaction)) NOT review NOT (children OR pediatrics OR paediatrics OR adolescent)).

Key findings

Rivaroxaban exhibits predictable pharmacokinetics and pharmacodynamics, and thus does not require routine coagulation monitoring, unlike vitamin K antagonists (e.g. warfarin). Rivaroxaban also has a lower potential for drug–drug and food–drug interactions compared with warfarin; however, co-administration with strong inhibitors of both cytochrome P450 3A4 and P-glycoprotein is not recommended. The data indicate that dose adjustment is not necessary for age, gender or body weight. The dosing regimens of rivaroxaban vary depending on the indication, and phase III studies have demonstrated a favourable benefit–risk profile of rivaroxaban compared with traditional standard of care.

Summary

Rivaroxaban may offer an anticoagulant option that could simplify and improve the management of patients with thromboembolic disorders.

Design and rationale for RE-VERSE AD: A phase 3 study of idarucizumab, a specific reversal agent for dabigatran

Idarucizumab, a Fab fragment directed against dabigatran, produced rapid and complete reversal of the anticoagulation effect of dabigatran in animals and in healthy volunteers. The Study of the REVERSal Effects of Idarucizumab in Patients on Active Dabigatran (RE-VERSE AD™) is a global phase 3 prospective cohort study aimed at investigating idarucizumab in dabigatran-treated patients who present with uncontrollable or life-threatening bleeding, and in those requiring urgent surgery or intervention. We describe the rationale for, and design of the trial (clinicaltrials.gov NCT02104947).

Real-world data confirm clinical trial outcomes for rivaroxaban in orthopaedic patients

Venous thromboembolism (VTE) is a potential cause of morbidity and mortality in patients after major orthopaedic surgery. Based on the results of the international phase III RECORD (Regulation of Coagulation in Orthopaedic Surgery to Prevent Deep Vein Thrombosis and Pulmonary Embolism) program, the oral, direct Factor Xa inhibitor rivaroxaban has been approved in many countries for the prevention of VTE after elective hip arthroplasty or knee arthroplasty. However, study results of randomized controlled trials may have limited generalizability to routine clinical practice in unselected patients. The phase IV XAMOS (Xarelto® in the Prophylaxis of Postsurgical Venous Throboembolism after Elective Major Orthopaedic Surgery of the Hip or Knee) study and the ORTHO-TEP (large single-center registry) collected real-world data to assess the effectiveness and safety of rivaroxaban compared with standard of care in large cohorts of patients undergoing major orthopaedic surgery. This review evaluates real-world data from XAMOS and ORTHO-TEP, confirming the favorable benefit–risk profile of rivaroxaban for the prevention of VTE in patients after major orthopaedic surgery that was demonstrated by the phase III RECORD studies in patients after elective hip or knee arthroplasty.

[Management of new oral anticoagulants in gastrointestinal bleeding and endoscopy]

New oral direct anticoagulants agents are alternatives to warfarin for long-term anticoagulation in a growing number of patients that require long-term anticoagulation for atrial fibrillation, deep venous thrombosis and pulmonary embolism. These new agents with predictable pharmacokinetic and pharmacodynamics profiles offer a favorable global safety profile, but increased gastrointestinal bleeding compared to the vitamin K antagonists. Many gastroenterologists are unfamiliar and may be wary of these newer drugs, since Clinical experience is limited and no specific antidote is available to reverse their anticoagulant effect. In this article the risk of these new agents and, how to manage these agents in both the presence of acute gastrointestinal bleeding and in patients undergoing endoscopic procedures is reviewed.

Rivaroxaban in the Treatment of Venous Thromboembolism and the Prevention of Recurrences

Anticoagulation therapy is the standard treatment of patients with symptomatic venous thromboembolism (VTE), including deep vein thrombosis and pulmonary embolism. Until recently, treatment of VTE was based on parenteral or low-molecular-weight heparin for initial therapy (5-10 days) and oral vitamin K antagonists for long-term therapy. Those treatments have some limitations, including parenteral administration (heparins), the need for frequent monitoring and dose adjustments, interactions with several medications, and dietary restrictions (vitamin K antagonists). Rivaroxaban is a new oral direct factor Xa inhibitor with a wide therapeutic window, predictable anticoagulant effect, no food interactions, and few drug interactions. Consequently, no periodic monitoring of anticoagulation is needed, and fixed doses can be prescribed. EINSTEIN program demonstrated that rivaroxaban was as effective as and significantly safer than standard therapy for treatment of VTE. Rivaroxaban was recently authorized so doubts exist about how to use it in daily clinical practice. This document aims to clarify common questions formulated by clinicians regarding the use of this new drug.

The management of dental patients taking new generation oral anticoagulants

Recently, new oral anticoagulants have been introduced as alternatives to warfarin. While national guidelines for treatment of dental patients taking warfarin as an anticoagulant are well-established, no such information is available for these novel therapeutic agents. At present, the local guidance available is contradictory between different health boards/health planning units, and liaison with the medical practitioner managing the individual patient's anticoagulation is imperative if any invasive procedure is proposed. This paper examines the available evidence regarding these drugs and sets out proposals for clinical guidance of dental practitioners treating these patients in primary dental care.

Cardiovascular, bleeding, and mortality risks in elderly Medicare patients treated with dabigatran or warfarin for nonvalvular atrial fibrillation

BACKGROUND

The comparative safety of dabigatran versus warfarin for treatment of nonvalvular atrial fibrillation in general practice settings has not been established.

METHODS AND RESULTS

We formed new-user cohorts of propensity score-matched elderly patients enrolled in Medicare who initiated dabigatran or warfarin for treatment of nonvalvular atrial fibrillation between October 2010 and December 2012. Among 134 414 patients with 37 587 person-years of follow-up, there were 2715 primary outcome events. The hazard ratios (95% confidence intervals) comparing dabigatran with warfarin (reference) were as follows: ischemic stroke, 0.80 (0.67-0.96); intracranial hemorrhage, 0.34 (0.26-0.46); major gastrointestinal bleeding, 1.28 (1.14-1.44); acute myocardial infarction, 0.92 (0.78-1.08); and death, 0.86 (0.77-0.96). In the subgroup treated with dabigatran 75 mg twice daily, there was no difference in risk compared with warfarin for any outcome except intracranial hemorrhage, in which case dabigatran risk was reduced. Most patients treated with dabigatran 75 mg twice daily appeared not to have severe renal impairment, the intended population for this dose. In the dabigatran 150-mg twice daily subgroup, the magnitude of effect for each outcome was greater than in the combined-dose analysis.

CONCLUSIONS

In general practice settings, dabigatran was associated with reduced risk of ischemic stroke, intracranial hemorrhage, and death and increased risk of major gastrointestinal hemorrhage compared with warfarin in elderly patients with nonvalvular atrial fibrillation. These associations were most pronounced in patients treated with dabigatran 150 mg twice daily, whereas the association of 75 mg twice daily with study outcomes was indistinguishable from warfarin except for a lower risk of intracranial hemorrhage with dabigatran.

[Hemorrhagic stroke and new oral anticoagulants]

The recent release of new oral anticoagulants (NOAC) raises the question of the management of intracranial hemorrhage occurring during treatment with these molecules. Dabigatran, rivaroxaban and apixaban have different pharmacological characteristics that physicians need to know to adjust their prescription to each patient. Studies of efficacy and safety prior to the marketing of these molecules showed a decreased risk of intracranial hemorrhage compared with vitamin K antagonists. However, no reliable data are available regarding the prognosis of these hemorrhages occurring during NOAC treatment. In addition, there is no specific antidote and reversal protocol validated in humans. So, physicians are in a difficult situation when critical bleeding occurs. The timing of recovering normal hemostatic capacity is then a determinant factor of prognosis. Studies in animals or healthy volunteers showed a correction of the biological parameters using prothrombin complex concentrates activated or not, without reducing the volume of hematoma. On this basis, proposals have been issued by the french group of interest for perioperative hemostasis (GIHP) for the management of bleeding under NOAC treatment, which include management of intracranial hemorrhage.

How do we manage cardiopulmonary bypass coagulopathy?

BACKGROUND

Patients who undergo cardiopulmonary bypass (CPB) are at risk for coagulopathy. Suboptimal turnaround time (TAT) of laboratory coagulation testing results in empiric administration of blood products to treat massive bleeding. We describe our initiative in establishing the coagulation-based hemotherapy (CBH) service, a clinical pathology consultation service that uses rapid TAT coagulation testing and provides comprehensive assessment of bleeding in patients undergoing CPB. A transfusion algorithm that treats the underlying cause of coagulopathy was developed.

STUDY DESIGN AND METHODS

The coagulation testing menu includes all aspects of coagulopathy with close proximity of the laboratory to the operating room to allow for rapid test results. The hemotherapy pathologist monitors laboratory results at several stages in surgery and uses a comprehensive algorithm to monitor a patient's hemostasis. The optimal number and type of blood products are selected when the patient is taken off CPB.

RESULTS

The CBH service was consulted for 44 ventricular assist device implants, 30 heart transplants, and 31 other cardiovascular surgeries from May 2012 through November 2013. The TAT for laboratory tests was 15 minutes for complete blood count, antithrombin, and coagulation panel and 30 minutes for VerifyNow and thromboelastography, in comparison to 45 to 60 minutes in normal settings. The transfusion algorithms were used with optimal administration of blood components with preliminary data suggestive of reduced blood product usage and better patient outcomes.

CONCLUSION

We described the successful introduction of a novel pathology consultation service that uses a rapid TAT coagulation testing menu with transfusion algorithms for improved management of CPB patients.

Anticoagulation in atrial fibrillation

Atrial fibrillation increases the risk of stroke, which is a leading cause of death and disability worldwide. The use of oral anticoagulation in patients with atrial fibrillation at moderate or high risk of stroke, estimated by established criteria, improves outcomes. However, to ensure that the benefits exceed the risks of bleeding, appropriate patient selection is essential. Vitamin K antagonism has been the mainstay of treatment; however, newer drugs with novel mechanisms are also available. These novel oral anticoagulants (direct thrombin inhibitors and factor Xa inhibitors) obviate many of warfarin's shortcomings, and they have demonstrated safety and efficacy in large randomized trials of patients with non-valvular atrial fibrillation. However, the management of patients taking warfarin or novel agents remains a clinical challenge. There are several important considerations when selecting anticoagulant therapy for patients with atrial fibrillation. This review will discuss the rationale for anticoagulation in patients with atrial fibrillation; risk stratification for treatment; available agents; the appropriate implementation of these agents; and additional, specific clinical considerations for treatment.

The role of rivaroxaban in atrial fibrillation and acute coronary syndromes

Rivaroxaban, a direct factor Xa inhibitor, is a novel oral anticoagulant approved for stroke prevention in patients with nonvalvular atrial fibrillation and also approved in Europe (but not in the United States) to prevent recurrent ischemic events in patients with recent acute coronary syndromes. Advantages of rivaroxaban over oral anticoagulants such as warfarin are the lack of need for ongoing monitoring, a fixed-dose regimen, and fewer drug and food interactions. Drawbacks include a lack of an antidote and the absence of a widely available method to reliably monitor the anticoagulant effect. In patients at risk of stroke due to atrial fibrillation, rivaroxaban was noninferior compared to warfarin in preventing stroke/systemic embolism in the Rivaroxaban Once Daily Oral Direct Factor Xa Inhibition Compared with Vitamin K Antagonism for Prevention of Stroke and Embolism Trial in Atrial Fibrillation (ROCKET-AF) trial and was associated with a similar risk of major bleeding; the incidence of intracranial hemorrhage was 33% lower with rivaroxaban. Concerns raised about the trial were the adequacy of warfarin management and the increase in event rate at the end of the trial. The drug acquisition cost of rivaroxaban is higher than that of warfarin although decision-analytic models suggest that it is cost effective in atrial fibrillation. In patients with recent acute coronary syndrome, low-dose rivaroxaban reduced mortality and the composite end point of death from cardiovascular causes, myocardial infarction and stroke, but this was accompanied by an increased risk of intracranial hemorrhage and major bleeding in the Rivaroxaban in Combination With Aspirin Alone or With Aspirin and a Thienopyridine in Patients With Acute Coronary Syndromes-Thrombolysis in Myocardial Infarction (ATLAS ACS 2-TIMI) 51 trial. Thus, rivaroxaban appears to be a valuable addition to the therapeutic armamentarium in atrial fibrillation although caution should be exercised, given the limited experience in combination with novel oral antiplatelet agents. The role of rivaroxaban as part of a modern regimen in acute coronary syndrome continues to be evaluated.

Evaluation and management of the atrial fibrillation patient: a report from the Society of Cardiovascular Patient Care

Atrial fibrillation (AF) is the most common cardiac dysrhythmia, and its prevalence is growing. The care of patients with AF is complex and involves multiple specialties and venues of care. Guideline recommendations are available for AF therapy; however, their implementation can be challenging. The Society of Cardiovascular Patient Care has developed an accreditation program, formulated by an expert committee on AF. Accreditation is based on specific criteria in 7 domains: (1) community outreach, (2) prehospital care, (3) early stabilization, (4) acute care, (5) transitions of care, (6) clinical quality measures, and (7) governance. This document presents the rationale, discussion, and supporting evidence for these criteria, in an effort to maximize effective and efficient AF care.

Rivaroxaban and hemostasis in emergency care

Rivaroxaban is an oral, direct Factor Xa inhibitor, approved for the prevention and treatment of several thromboembolic disorders. Rivaroxaban does not require routine coagulation monitoring and has a short half-life. However, confirmation of rivaroxaban levels may be required in circumstances such as life-threatening bleeding or perioperative management. Here, we explore the management strategies in patients receiving rivaroxaban who have a bleeding emergency or require emergency surgery. Rivaroxaban plasma concentrations can be assessed quantitatively using anti-Factor Xa chromogenic assays, or qualitatively using prothrombin time assays (using rivaroxaban-sensitive reagents). In patients receiving long-term rivaroxaban therapy who require elective surgery, discontinuation of rivaroxaban 20–30 hours beforehand is normally sufficient to minimize bleeding risk. For emergency surgery, we advise against prophylactic use of hemostatic blood products, even with high rivaroxaban concentrations. Temporary rivaroxaban discontinuation is recommended if minor bleeding occurs; for severe bleeding, rivaroxaban withdrawal may be necessary, along with compression or appropriate surgical treatment. Supportive measures such as blood product administration might be beneficial. Life-threatening bleeding demands comprehensive hemostasis management, including potential use of agents such as prothrombin complex concentrate. Patients taking rivaroxaban who require emergency care for bleeding or surgery can be managed using established protocols and individualized assessment.

New anticoagulants and antiplatelet agents: a primer for the clinical gastroenterologist

The discovery of the first oral anticoagulant, warfarin, was a milestone in anticoagulation. Warfarin's well-known limitations, however, have led to the recent development of more effective anticoagulants. The rapidly growing list of these drugs, however, presents a challenge to endoscopists who must treat patients on these sundry medications. This review is intended to summarize the pharmacological highlights of new anticoagulants, with particular attention to suggested "best-practice" recommendations for the withholding of these drugs before endoscopic procedures.

Practical management of patients on apixaban: a consensus guide

BACKGROUND

Atrial fibrillation (AF) is a common tachyarrhythmia in Australia, with a prevalence over 10% in older patients. AF is the leading preventable cause of ischaemic stroke, and strokes due to AF have a higher mortality and morbidity. Stroke prevention is therefore a key management strategy for AF patients, in addition to rate and rhythm control. Anticoagulation with warfarin has been an enduring gold standard for stroke prevention in NVAF patients. In Australia, three novel oral anticoagulants (NOACs), apixaban, dabigatran and rivaroxaban are now approved and reimbursed for stroke prevention in patients with non-valvular AF (NVAF). International European Cardiology guidelines now recommend either a NOAC or warfarin for NVAF patients with a CHA2DS2-VASc score ≥2, unless contraindicated. Apixaban is a direct factor Xa inhibitor with a 12-hour half-life and 25% renal excretion that was found in a large trial of NVAF patients to be superior to warfarin in preventing stroke or systemic embolism. In this trial population, apixaban also resulted in less bleeding and a lower mortality rate than warfarin.

METHODS

Clinical experience with apixaban outside of clinical trials has been limited, and there is currently little evidence to guide the management of bleeding or invasive procedures in patients taking apixaban. The relevant currently available animal and ex vivo human data were collected, analyzed and summarized.

RESULTS

This multi-disciplinary consensus statement has been written to serve as a guide for healthcare practitioners prescribing apixaban in Australia, with a focus on acute and emergency management.

CONCLUSIONS

The predictable pharmacokinetics and minimal drug interactions of apixaban should allow for safe anticoagulation in the majority of patients, including temporary interruption for elective procedures. In the absence of published data, patients actively bleeding on apixaban should receive standard supportive treatment. Quantitative assays of apixaban level such as chromogenic anti-Xa assays are becoming available but their utility is unproven in this setting. Specific antidotes for novel anticoagulants, including apixaban, are in clinical development.

Positive outcome after intentional overdose of dabigatran

INTRODUCTION

Dabigatran (Pradaxa™), an orally active direct thrombin inhibitor, was approved by the United States Food and Drug Administration for the prevention of stroke in patients with atrial fibrillation in October 2010. Life-threatening consequences from dabigatran therapy include hemorrhage and bleeding complications, but they typically occur after renal impairment. We describe the first case report of intentional, acute overdose with dabigatran.

CASE REPORT

A 57-year-old woman with a medical history of depression and atrial fibrillation presented to the emergency department after ingesting 11.25 g of dabigatran in a suicide attempt. Despite an ecchymosis indicative of prior trauma, there was no evidence of acute bleeding. After receiving gastric lavage and activated charcoal therapy in the emergency department, she was admitted to the ICU. On presentation, dabigatran blood levels measured 970 ng/mL and thrombin clot times measured above the testable limits (>120 s) until 52 h post-arrival. The remainder of her clinical course was uncomplicated, and the patient was transferred to an inpatient psychiatric unit for depression follow-up.

DISCUSSION

This case shows the clinical course of a patient with an acute, massive dabigatran overdose with no significant clinical consequences. Currently, there is no ideal method to monitor anticoagulation levels; there is no pharmacologic reversal method, and hemodialysis is an undesirable treatment option.

Pros and cons of new oral anticoagulants

The availability of new oral anticoagulants (NOACs) targeting either thrombin (dabigatran etexilate) or factor Xa (rivaroxaban and apixaban) for the prevention and treatment of thrombosis has been highly anticipated. NOACs have major pharmacologic advantages over vitamin K antagonists (eg, warfarin), including rapid onset/offset of action, few drug interactions, and predictable pharmacokinetics, eliminating the requirement for regular coagulation monitoring. Regulatory agencies have approved several NOACs for specific indications based on the results of clinical trials demonstrating efficacy and safety that are at least as good, if not better, than warfarin (for stroke prevention in atrial fibrillation and treatment and secondary prevention of venous thromboembolism) or low-molecular-weight heparin, which is injectable (for initial treatment of venous thromboembolism and thromboprophylaxis in patients undergoing hip or knee arthroplasty). However, the adoption of this new therapeutic class into clinical practice has been slower than expected due to several factors including concerns regarding medication adherence without laboratory monitoring, uncertainty about dosing in some patient populations (eg, renal dysfunction, marked extremes of body weight), and higher drug costs compared with warfarin. Other issues are the current absence of specific antidotes for NOACs and assays to measure drug levels at most centers. The indications for NOACs on the market will expand and at least one additional agent (edoxaban) will likely gain approval within the next 2 years. As practitioners gain familiarity with the drugs and healthcare systems adapt to their use, NOAC use will increase substantially over time. Warfarin, however, will continue to be an appropriate anticoagulant choice for many patients.

Reversal of apixaban induced alterations in hemostasis by different coagulation factor concentrates: significance of studies in vitro with circulating human blood

Apixaban is a new oral anticoagulant with a specific inhibitory action on FXa. No information is available on the reversal of the antihemostatic action of apixaban in experimental or clinical settings. We have evaluated the effectiveness of different factor concentrates at reversing modifications of hemostatic mechanisms induced by moderately elevated concentrations of apixaban (200 ng/ml) added in vitro to blood from healthy donors (n = 10). Effects on thrombin generation (TG) and thromboelastometry (TEM) parameters were assessed. Modifications in platelet adhesive, aggregating and procoagulant activities were evaluated in studies with blood circulating through damaged vascular surfaces, at a shear rate of 600 s(-1). The potential of prothrombin complex concentrates (PCCs; 50 IU/kg), activated prothrombin complex concentrates (aPCCs; 75 IU/kg), or activated recombinant factor VII (rFVIIa; 270 μg/kg), at reversing the antihemostatic actions of apixaban, were investigated. Apixaban interfered with TG kinetics. Delayed lag phase, prolonged time to peak and reduced peak values, were improved by the different concentrates, though modifications in TG patterns were diversely affected depending on the activating reagents. Apixaban significantly prolonged clotting times (CTs) in TEM studies. Prolongations in CTs were corrected by the different concentrates with variable efficacies (rFVIIa≥aPCC>PCC). Apixaban significantly reduced fibrin and platelet interactions with damaged vascular surfaces in perfusion studies (p<0.05 and p<0.01, respectively). Impairments in fibrin formation were normalized by the different concentrates. Only rFVIIa significantly restored levels of platelet deposition. Alterations in hemostasis induced by apixaban were variably compensated by the different factor concentrates investigated. However, effects of these concentrates were not homogeneous in all the tests, with PCCs showing more efficacy in TG, and rFVIIa being more effective on TEM and perfusion studies. Our results indicate that rFVIIa, PCCs and aPCCs have the potential to restore platelet and fibrin components of the hemostasis previously altered by apixaban.

Cost-effectiveness of rivaroxaban versus warfarin anticoagulation for the prevention of recurrent venous thromboembolism: a U.S. perspective

INTRODUCTION

Rivaroxaban is an oral direct factor Xa inhibitor that is noninferior to warfarin in the prevention of recurrent venous thromboembolism (VTE). Whether rivaroxaban is cost-effective in the prevention of recurrent VTE, however, is not known.

MATERIAL AND METHODS

To assess the cost effectiveness of rivaroxaban compared with warfarin in the prevention of recurrent VTE, we built a Markov state-transition model over a 10-year time horizon. The base case analysis consisted of a hypothetical cohort of 60-year-old patients with an initial VTE who received secondary prophylaxis with either rivaroxaban or warfarin for 3 to 12months. Cost estimates were derived from the Healthcare and Utilization Project and other sources. Probabilities were based on literature values. Outcomes included costs in 2011 United States dollars, quality-adjusted life-years (QALYs), and incremental cost effectiveness ratios (ICERs) over 10years from a societal perspective.

RESULTS

Compared with warfarin, the rivaroxaban strategy cost less ($3,195 vs. $6,188) and was more effective (9.29 QALYs vs 9.14 QALYs). Our results were highly robust in sensitivity analyses. Warfarin was no longer dominated by rivaroxaban when the risk of major bleeding with rivaroxaban exceeds 3.8% (base case estimate: 0.96%).

CONCLUSION

In summary, prophylactic anticoagulation with rivaroxaban appears to be a cost effective, and perhaps cost saving, alternative to warfarin for the prevention of recurrent VTE.

Importance of pharmacokinetic profile and variability as determinants of dose and response to dabigatran, rivaroxaban, and apixaban

Warfarin has been the mainstay oral anticoagulant (OAC) medication prescribed for stroke prevention in atrial fibrillation (AF) patients. However, warfarin therapy is challenging because of marked interindividual variability in dose and response, requiring frequent monitoring and dose titration. These limitations have prompted the clinical development of new OACs (NOACs) that directly target the coagulation cascade with rapid onset/offset of action, lower risk for drug-drug interactions, and more predictable response. Recently, NOACs dabigatran (direct thrombin inhibitor), and rivaroxaban and apixaban (factor Xa [FXa] inhibitors) have gained regulatory approval as alternative therapies to warfarin. Though the anticoagulation efficacy of these NOACs has been characterized, differences in their pharmacokinetic and pharmacodynamic profiles have become a significant consideration in terms of drug selection and dosing. In this review, we outline key pharmacokinetic and pharmacodynamic features of each compound and provide guidance on selection and dosing of the 3 NOACs relative to warfarin when considering OAC therapy for AF patients. Importantly, we show that by better understanding the effect of clinical variables such as age, renal function, dosing interval, and drug metabolism (CYP3A4) and transport (P-glycoprotein), we might be able to better predict the risk for sub- and supratherapeutic anticoagulation response and individualize OAC selection and dosing.

The role of the laboratory in treatment with new oral anticoagulants

Orally active small molecules that selectively and specifically inhibit coagulation serine proteases have been developed for clinical use. Dabigatran etexilate, rivaroxaban and apixaban are given at fixed doses and do not require monitoring. In most circumstances, these drugs have predictable bioavailability, pharmacokinetic effects, and pharmacodynamic effects. However, there will be clinical circumstances when assessment of the anticoagulant effect of these drugs will be required. The effect of these drugs on laboratory tests has been determined in vitro by spiking normal samples with a known concentration of active compound, or ex vivo by using plasma samples from volunteers and patients. Data on the sensitivity of different reagents are now available, and so guidance as to the effect and interpretation of a test result is now possible. Laboratories should be aware of the sensitivity of their own assays to each drug. This may be achieved by using appropriate calibrated plasma samples.

A chemically-modified inactive antithrombin as a potent antagonist of fondaparinux and heparin anticoagulant activity

BACKGROUND

Heparin and its analogs, mediating their anticoagulant activity through antithrombin (AT) activation, remain largely used for the preventive and curative treatment of thrombosis. The major adverse reaction of these drugs is the bleeding risk associated with overdose. Unfractionnated heparin (UFH) can be efficiently and rapidly neutralized by protamine sulfate, but this reversal partially neutralizes low-molecular-weight heparin (LMWH) and is inefficient in reversing fondaparinux. To secure administration of AT-mediated anticoagulants and counteract bleeding disorders, we previously designed a recombinant inactive AT as an antidote to heparin derivatives.

OBJECTIVES

To get around the limited production level of recombinant AT, we propose in this study an alternative strategy to produce a chemically modified inactive AT, exhibiting increased heparin affinity, as an antagonist of heparin analogs.

METHODS

Plasma-derived AT was chemically modified with 2,3 butanedione, a diketone known to specifically react with the arginine side chain. The chemical reaction was conducted in the presence of heparin to preserve basic residues within the heparin binding site from modifications.

RESULTS

AT treated by butanedione and selected for its high heparin affinity (AT-BD) was indeed modified on reactive Arg393 and thus exhibited decreased anticoagulant activity and increased heparin affinity. AT-BD was able to neutralize anticoagulant activity of heparin derivatives in vitro and in vivo and was devoid of intrinsic anticoagulant activity, as assessed by activated partial thromboplastin time assay.

CONCLUSIONS

AT-BD appears to be as efficient as protamine to neutralize UFH in vivo but could be more largely used because it also reverses fondaparinux and LMWH.

Rivaroxaban: practical considerations for ensuring safety and efficacy

Rivaroxaban is the first agent available within a new class of anticoagulants called direct factor Xa inhibitors. Rivaroxaban is approved for use in the United States for the prevention of stroke and systemic embolism in patients with nonvalvular atrial fibrillation, for the prevention of deep vein thrombosis in patients undergoing total hip replacement and total knee replacement, for the treatment of deep vein thrombosis and pulmonary embolism, and for the reduction in risk of recurrence of deep vein thrombosis and pulmonary embolism (with additional indications under review). Rivaroxaban dose and frequency of administration vary depending on the indication. As of result of predictable pharmacokinetics and pharmacodynamics, a fixed dose of rivaroxaban is administered without routine coagulation testing. Rivaroxaban has a short half-life, undergoes a dual mode of elimination (hepatic and renal), and is a substrate for P-glycoprotein. Rivaroxaban has a lower potential for drug interactions compared with warfarin. Despite the advantages of a once/day fixed-dose oral agent, in many clinical situations limited evidence is available to guide optimal management of rivaroxaban therapy. In this article, we review the available evidence and provide recommendations where possible for such situations including the desire to monitor the anticoagulation intensity, use in special patient populations, managing drug interactions, and transitioning across anticoagulant agents. Potential strategies for reversing rivaroxaban's anticoagulant effect are reviewed. Health systems will need to perform a systematic safety evaluation and ensure that numerous hospital policies related to anticoagulation are updated to include rivaroxaban. A comprehensive approach to education is needed for clinicians, patients, and technical support personnel involved in patient interactions to ensure safe use.

Recommendations for the emergency management of complications associated with the new direct oral anticoagulants (DOACs), apixaban, dabigatran and rivaroxaban

Dabigatran, apixaban, and rivaroxaban have been approved for primary and secondary stroke prevention in patients with atrial fibrillation. However, questions have arisen about how to manage emergency situations, such as when thrombolysis would be required for acute ischemic stroke or for the managing intracranial or gastrointestinal bleedings. We summarize the current literature and provide recommendations for the management of these situations. Peak plasma levels of the direct oral anticoagulants (DOACs) apixaban, dabigatran, or rivaroxaban are observed about 2-4 h after intake. Elimination of dabigatran is mainly dependent on renal function. Consequently, if renal function is impaired, there is a risk of drug accumulation that is highest for dabigatran followed by rivaroxaban and then apixaban and thus dosing recommendations are different. To date, no bedside tests are available that reliably assess the anticoagulatory effect of DOACs, nor are specific antidotes available. We recommend performing the following tests if DOAC intake is unknown: dabigatran-associated bleeding risk is minimized or can be neglected if thrombin time, Hemoclot test, or Ecarin clotting time is normal. Apixaban and rivaroxaban effects can be ruled out if findings from the anti-factor Xa activity test are normal. High plasma levels of DOAC are also mostly excluded if PTT and PTZ are normal four or more hours after DOAC intake. However, normal values of global coagulation tests are not sufficient if thrombolysis is indicated for treating acute stroke. The decision for or against thrombolysis is an individual decision; in these cases, thrombolysis use is off-label. In case of bleeding, prothrombin complex concentrates seems to be the most plausible treatment. For severe gastrointestinal bleeding with life-threatening blood loss, the bleeding source needs to be identified and treated by invasive measures. Use of procoagulant drugs (antifibrinolytics) might also be considered. However, there is very limited clinical experience with these products in conjunction with DOAC.

Reversal of oral anticoagulation

Although the use of dabigatran and rivaroxaban are increasing, data on the reversal of their effects are limited. The lack of reliable monitoring methods and specific reversal agents renders treatment strategies empirical, and as a result, treatment consists mainly of supportive measures. Therefore, we performed a systematic search of the PubMed database to find studies and reviews pertaining to oral anticoagulation reversal strategies. This review discusses current anticoagulation reversal recommendations for the oral anticoagulants warfarin, dabigatran, and rivaroxaban for patients at a heightened risk of bleeding, actively bleeding, or those in need of preprocedural anticoagulation reversal. We highlight the literature that shaped these recommendations and provide directions for future research to address knowledge gaps. Although reliable recommendations are available for anticoagulation reversal in patients treated with warfarin, guidance on the reversal of dabigatran and rivaroxaban is varied and equivocal. Given the increasing use of the newer agents, focused research is needed to identify effective reversal strategies and develop and implement an accurate method (assay) to guide reversal of the newer agents. Determining patient-specific factors that influence the effectiveness of reversal treatments and comparing the effectiveness of various treatment strategies are pertinent areas for future anticoagulation reversal research.

Novel oral anticoagulants for stroke prevention in patients with atrial fibrillation: dawn of a new era

Atrial fibrillation (AF) is an important cause of ischemic stroke and is the underlying cause of > 20% of all strokes, with increasing age being a risk factor. Until recently, warfarin was the only available oral anticoagulant used to decrease this risk in patients with AF. However, there are several disadvantages of warfarin use, such as the requirement for monitoring the international normalized ratio, its wide range of drug-food interactions, and its narrow therapeutic index. Thus, there has been a strong impetus for the development of newer oral anticoagulants with predictable pharmacokinetics that obviate the need for monitoring the international normalized ratio. The US Food and Drug Administration has approved a direct thrombin inhibitor (dabigatran) and 2 factor Xa inhibitors (rivaroxaban and apixaban) for stroke prevention in patients with nonvalvular AF. There are several other new oral anticoagulant agents on the horizon, including the factor Xa inhibitor edoxaban. This review article discusses the pharmacological properties, clinical trial data, and practical issues associated with the use of these novel oral anticoagulants.

Review of recently approved alternatives to anticoagulation with warfarin for emergency clinicians

BACKGROUND

Dabigatran and rivaroxaban are novel anticoagulants that have been approved for the prevention of thromboembolic events in atrial fibrillation. These medications are attractive to both patients and clinicians, as, unlike warfarin, they do not require laboratory monitoring or dietary restrictions. However, they carry bleeding risks similar to that of warfarin and are without a reliable reversal agent.

OBJECTIVES

The objectives of this article are to 1) summarize the pivotal trials leading to the U.S. Food and Drug Administration approvals of dabigatran (Pradaxa; Boehringer Ingelheim, Ridgefield, CT) and rivaroxaban (Xarelto; Janssen Pharmaceuticals, Inc., Titusville, NJ); 2) present the limited data available regarding the management of bleeding patients on these agents; and 3) provide suggestions to guide emergency providers given the limited data.

DISCUSSION

Dabigatran and rivaroxaban were approved based on large, non-inferiority trials comparing the new agents to warfarin with stroke or systemic embolism as the primary outcome. Traditional coagulation studies cannot be used to determine the degree of anti-coagulation produced by these agents. Fresh frozen plasma is unlikely to be effective in patients on these drugs who are acutely bleeding. Prothrombin complex concentrate can be considered in patients on rivaroxaban. Dabigatran is renally cleared, so dabigatran could be removed by hemodialysis. Theoretically, DDAVP (Sanofi-Aventis U.S. LLC, Bridgewater, NJ), aminocaproic acid, tranexamic acid, or recombinant activated factor VII could also be used in an attempt to control bleeding.

CONCLUSION

There is a need for assays for the degree of anticoagulation produced by drugs such as dabigatran and rivaroxaban. Additionally, studies are needed to evaluate reversal agents that could be effective in the setting of acute bleeding.

Advances in the management of the critically injured patient in the operating room

Care of trauma patients continues to improve through better understanding of optimal timing of operating room (OR) interventions, improved monitoring for patients with head injury and hemodynamic compromise, optimization of volume status, and use of appropriate vasoactive agents. Investigation of the pathophysiology of trauma patients as they progress to the chronic phase continues to advance interventions in the ICU and the OR. This article is an evidence-based update of anesthetic considerations for these patients, including management of intracranial pressure, cardiac monitoring, management of the damage control abdomen, fluid and hemodynamic management, and control of coagulopathies.