Comparative Pharmacodynamics and Pharmacokinetics of Oral Direct Thrombin and Factor Xa Inhibitors in Development

Palladium-catalyzed oxidative carbamoylation of isoquinoline N-oxides with formylamides by means of dual C–H oxidative coupling

A new palladium-catalyzed oxidative carbamoylation reaction of isoquinoline N-oxides with formylamides for the synthesis of isoquinoline-1-carboxamides is described.

Treatment options for venous thromboembolism: lessons learnt from clinical trials

Venous thromboembolism (VTE), comprising deep vein thrombosis and pulmonary embolism, is a common condition associated with a significant clinical and economic burden. Anticoagulant therapy is the mainstay of treatment for VTE, having been shown to reduce the risk of death in patients with pulmonary embolism, and recurrence or extension of thrombi in patients with deep vein thrombosis during the initial treatment period. Long-term anticoagulation is indicated in some individuals with VTE, depending on individual risk of VTE recurrence and anticoagulant-related bleeding. Management of VTE in clinical practice is often complex because patients' characteristics and treatment needs may differ considerably from those encountered in clinical trials. Current guidelines recommend the use of either low molecular weight heparins or fondaparinux overlapping with and followed by a vitamin K antagonist for the initial treatment of VTE, with the vitamin K antagonist continued when long-term anticoagulation is required. These traditional anticoagulants have practical limitations that have led to the development of direct oral anticoagulants that directly target either Factor Xa or thrombin and are administered at a fixed dose without the need for routine coagulation monitoring. This review discusses practical considerations for hospital physicians and haematologists in the management of VTE treatment, including the potential for the direct oral anticoagulants to simplify treatment.

Practical considerations in the use of novel oral anticoagulants for stroke prevention in nonvalvular atrial fibrillation

Atrial fibrillation (AF) is a highly prevalent cardiac arrhythmia associated with an increased risk of stroke. The role of anticoagulation therapy in the prevention of thrombosis and stroke is of critical importance for patients with AF. Limitations with vitamin K antagonists (VKAs), the current standard of care, have led to the development of novel oral anticoagulants (NOACs) that target either thrombin (dabigatran etexilate) or activated factor X (rivaroxaban, apixaban, and edoxaban). In comparison with traditional VKAs such as warfarin, these NOACs offer several pharmacologic advantages, including rapid onset of action, no significant food interactions, low potential for drug-drug interactions, and no requirement for routine coagulation monitoring. Completed phase-III clinical trials have demonstrated the therapeutic potential of dabigatran, rivaroxaban, and apixaban in comparison with warfarin for stroke prevention in patients with nonvalvular AF (NVAF). While the future utility of NOACs in preventing stroke in patients with NVAF looks promising, several practical issues, including the current lack of a reversal strategy and use of these agents in older patients with renal dysfunction, must be considered. Clinician and patient understanding of such issues will be important for the safe and effective use of NOACs.

The potential role of anticoagulant therapy for the secondary prevention of ischemic events post-acute coronary syndrome

Abstract The use of dual antiplatelet therapy has led to a substantial reduction in ischemic events post-acute coronary syndrome (ACS). Despite this, recurrent event rates remain high. Recent research has combined antiplatelet with anticoagulant therapy to reduce recurrent event rates further. Compared with standard medical therapy, rivaroxaban demonstrated improved efficacy outcomes and significantly reduced mortality after an ACS. Although clear benefits of novel oral anticoagulants post-ACS have been proven, concerns regarding bleeding are still a barrier to widespread use. This review explores key trials of dual antiplatelet therapy and examines the latest research in anticoagulation aiming to optimize clinical outcomes post-ACS.

Trials of novel oral anticoagulants for stroke prevention in patients with non-valvular atrial fibrillation

Patients with non-valvular atrial fibrillation (AF) face an increased risk of stroke compared with those in normal sinus rhythm. The vitamin K antagonist warfarin, available for over half a century, is highly effective in reducing the risk of stroke in patients with AF, but it is a difficult drug to use properly. As a result, it is challenging to keep the anticoagulant effect of warfarin in the desired range. Newer oral anticoagulants (NOACs) that directly inhibit Factor IIa (thrombin) or Factor Xa provide reliable anticoagulation when administer in fixed oral doses without routine coagulation monitoring. This manuscript will review in detail the pivotal trials of these NOACs that led to their approval as well as comment on the factors that should influence their selection.

The pharmacology of novel oral anticoagulants

Anticoagulation for the prevention of stroke is an important aspect of the management of atrial fibrillation. Novel anticoagulants including oral factor Xa inhibitors rivaroxaban and apixaban and the direct thrombin inhibitor dabigatran have emerged as important therapeutic treatment options for prevention of stroke in non-valvular atrial fibrillation. These agents offer practical advantages over traditional vitamin K antagonists, however an understanding of their individual pharmacokinetic and other agent-specific differences is essential for identifying appropriate candidates for therapy, and for selecting the appropriate agent that will be effective and safe. Here, we review the pharmacokinetic process of oral medication use, summarize the newer anticoagulants, their pharmacology, individual pharmacokinetic features, and explore possible explanations for the differences in bleeding outcomes observed in the clinical trials.

Structure-function relationships of factor Xa inhibitors: implications for the practicing clinician

The recent development and approval of novel oral anticoagulants represents a significant success in the intelligent design of target-specific therapeutics. However, while these agents obviate many of the shortcomings of their predecessor (warfarin), they present novel challenges in pharmacologic management as well. Each was designed to have high oral bioavailability and high affinity for its target molecule, conveying significant anticoagulant effects. Yet, such unique drug-ligand binding, coupled with unfamiliar drug interactions and renal-based clearance, represent challenges to clinical management. The current review describes the development and pharmacokinetic properties of these agents, in the context of their clinical utility and pitfalls.

Race against the clock: overcoming challenges in the management of anticoagulant-associated intracerebral hemorrhage

Patients receiving anticoagulation therapy who present with any type of intracranial hemorrhage--including subdural hematoma, epidural hematoma, subarachnoid hemorrhage, and intracerebral hemorrhage (ICH)--require urgent correction of their coagulopathy to prevent hemorrhage expansion, limit tissue damage, and facilitate surgical intervention as necessary. The focus of this review is acute ICH, but the principles of management for anticoagulation-associated ICH (AAICH) apply to patients with all types of intracranial hemorrhage, whether acute or chronic. A number of therapies--including fresh frozen plasma (FFP), intravenous vitamin K, activated and inactivated prothrombin complex concentrates (PCCs), and recombinant activated factor VII (rFVIIa)--have been used alone or in combination to treat AAICH to reverse anticoagulation, help achieve hemodynamic stability, limit hematoma expansion, and prepare the patient for possible surgical intervention. However, there is a paucity of high-quality data to direct such therapy. The use of 3-factor PCC (activated and inactivated) and rFVIIa to treat AAICH constitutes off-label use of these therapies in the United States. However, in April 2013, the US Food and Drug Administration (FDA) approved Kcentra (a 4-factor PCC) for the urgent reversal of vitamin K antagonist (VKA) anticoagulation in adults with acute major bleeding. Plasma is the only other product approved for this use in the United States. (1) Inconsistent recommendations, significant barriers (e.g., clinician-, therapy-, or logistics-based barriers), and a lack of approved treatment pathways in some institutions can be potential impediments to timely and evidence-based management of AAICH with available therapies. Patient assessment, therapy selection, whether to use a reversal or factor repletion agent alone or in combination with other agents, determination of site-of-care management, eligibility for neurosurgery, and potential hematoma evacuation are the responsibilities of the neurosurgeon, but ultimate success requires a multidisciplinary approach with consultation from the emergency department (ED) physician, pharmacist, hematologist, intensivist, neurologist, and, in some cases, the trauma surgeon.

Safety and efficacy of edoxaban, an oral factor Xa inhibitor, versus enoxaparin for thromboprophylaxis after total knee arthroplasty: the STARS E-3 trial

INTRODUCTION

This phase 3 trial compared the safety and efficacy of edoxaban, an oral direct factor Xa inhibitor, with enoxaparin sodium (enoxaparin) for thromboprophylaxis after total knee arthroplasty (TKA) in patients in Japan and Taiwan.

MATERIALS AND METHODS

In this randomized, double-blind, double-dummy study, patients received oral edoxaban 30 mg once daily beginning 6 to 24 hours postsurgery or enoxaparin 2000 IU (equivalent to 20 mg) subcutaneously twice daily beginning 24 to 36 hours postsurgery for 11 to 14 days. The primary efficacy endpoint was the composite of symptomatic pulmonary embolism and symptomatic and asymptomatic deep vein thrombosis. Safety endpoints included the incidence of major bleeding, clinically relevant non-major (CRNM) bleeding, major bleeding or CRNM bleeding, all bleeding events, adverse events, and adverse drug reactions.

RESULTS

Of 716 patients enrolled, 360 and 356 were randomized to receive edoxaban or enoxaparin, respectively. The primary efficacy outcome occurred in 22/299 (7.4%) and 41/295 (13.9%) patients in the edoxaban and enoxaparin groups, respectively (relative risk reduction=46.8%), indicating non-inferiority (P <0.001) and superiority (P=0.010) of edoxaban versus enoxaparin. In the edoxaban and enoxaparin groups, major bleeding occurred in 4/354 (1.1%) versus 1/349 (0.3%) patients (P=0.373); major or CRNM bleeding occurred in 22/354 (6.2%) versus 13/349 (3.7%) patients (P=0.129), respectively.

CONCLUSIONS

Edoxaban 30 mg once daily was more effective for thromboprophylaxis than subcutaneous enoxaparin 2000 IU twice daily following TKA and demonstrated a similar incidence of bleeding events.

Management of non-vitamin K antagonist oral anticoagulants in the perioperative setting

The field of oral anticoagulation has evolved with the arrival of non-vitamin K antagonist oral anticoagulants (NOACs) including an anti-IIa agent (dabigatran etexilate) and anti-Xa agents (rivaroxaban and apixaban). The main specificities of these drugs are predictable pharmacokinetics and pharmacodynamics but special attention should be paid in the elderly, in case of renal dysfunction and in case of emergency. In addition, their perioperative management is challenging, especially with the absence of specific antidotes. Effectively, periods of interruption before surgery or invasive procedures depend on half-life and keeping a permanent balance between bleeding and thromboembolic risks. In addition, few data regarding the link between plasma concentrations and their effects are provided. Routine laboratory tests are altered by NOACs and quantitative measurements are not widely performed. This paper provides a review on the management of NOACs in the perioperative setting, including the estimation of the bleeding and thrombotic risk, the periods of interruption, the indication of heparin bridging, the usefulness of laboratory tests before surgery or invasive procedure, and the time of resuming. Most data are based on expert's opinions.

Direct oral anticoagulants as alternative treatment options for the effective long-term treatment of patients with pulmonary embolism in primary care: a review

Pulmonary embolism (PE) represents a potentially life-threatening venous thromboembolic disorder, and prompt treatment is vital to prevent early mortality. However, diagnosis of PE is complicated by the range of signs and symptoms with which it presents. Clinical risk scores, imaging techniques, and laboratory tests are recommended in clinical guidelines to aid diagnosis, and risk stratification strategies can be used to inform treatment decisions. Long-term anticoagulation is key to avoid the risk of later complications of acute PE, such as recurrent venous thromboembolism and chronic thromboembolic pulmonary hypertension. Rivaroxaban is a direct oral anticoagulant that has been approved for the treatment of PE (and deep vein thrombosis) and prevention of recurrent venous thromboembolism; other direct oral anticoagulants have undergone phase III trials for these indications. These agents may provide advantages over traditional anticoagulants, such as vitamin K antagonists, because they are administered at fixed doses and do not require routine coagulation monitoring. These advantages may improve patient adherence and aid general practitioners by simplifying long-term management of PE in daily primary care.

[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.

Evolving practices in critical care and their influence on acute kidney injury

PURPOSE OF REVIEW

This review highlights the principal advances in critical care over the past year, and discusses the impact of these advances on the diagnosis and management of acute kidney injury (AKI).

RECENT FINDINGS

Recent literature has focused on assessment of volume status and fluid management, particularly in the setting of respiratory and cardiac failure. Other critical care topics are reviewed using a system-based approach.

SUMMARY

The incidence of AKI appears to be increasing, and despite advances in the provision of critical care and renal replacement therapies, there has been little improvement in its associated morbidity and mortality. Nonetheless, recent advances in critical care will impact the diagnosis and management of AKI, as well as shape the future research agenda. Continued work in the fields of critical care and nephrology will undoubtedly be centered on improved biomarkers for the detection of AKI, specific therapies to mitigate or reverse AKI, and techniques to prevent the development of AKI in the critically ill population.

Management of the bleeding patient receiving new oral anticoagulants: a role for prothrombin complex concentrates

Ease of dosing and simplicity of monitoring make new oral anticoagulants an attractive therapy in a growing range of clinical conditions. However, newer oral anticoagulants interact with the coagulation cascade in different ways than traditional warfarin therapy. Replacement of clotting factors will not reverse the effects of dabigatran, rivaroxaban, or apixaban. Currently, antidotes for these drugs are not widely available. Fortunately, withholding the anticoagulant and dialysis are freqnently effective treatments, particularly with rivaroxaban and dabigatran. Emergent bleeding, however, requires utilization of Prothrombin Complex Concentrates (PCCs). PCCs, in addition to recombinant factor VIIa, are used to activate the clotting system to reverse the effects of the new oral anticoagulants. In cases of refractory or emergent bleeding, the recommended factor concentrate in our protocols differs between the new oral anticoagulants. In patients taking dabigatran, we administer an activated PCC (aPCC) [FELBA] due to reported benefit in human in vitro studies. Based on human clinical trial evidence, the 4-factor PCC (Kcentra) is suggested for patients with refractory rivaroxaban- or apixaban-associated hemorrhage. If bleeding continues, recombinant factor VIIa may be employed. With all of these new procoagulant agents, the risk of thrombosis associated with administration of factor concentrates must be weighed against the relative risk of hemorrhage.

New oral pharmacotherapeutic agents for venous thromboprophylaxis after total hip arthroplasty

Patients undergoing total hip arthroplasty (THA) are at high risk for developing venous thromboembolism and, therefore, require short term prophylaxis with antithrombotic agents. Recently, target specific oral anticoagulants (TSOA) including the direct thrombin inhibitor, dabigatran, and the factor Xa inhibitors rivaroxaban, apixaban, and edoxaban have been approved for THA thrombopropylaxis in various countries. The TSOAs provide a rapid acting, oral alternative to parenteral agents including low-molecular weight heparins (LMWH) and fondaparinux; and compared to warfarin, they do not require routine laboratory monitoring and possess much fewer drug-drug interactions. Based on phase III clinical studies, TSOAs have established themselves as an effective and safe option for thromboprophylaxis after THA compared to LMWH, particularly enoxaparin, but require additional evaluation in specific populations such as the renally impaired or elderly. The ability to monitor and reverse these TSOAs in the case of bleeding complications or suspected sub- or supra-therapeutic anticoagulation is of importance, but remains investigational. This review will focus on the drug-specific characteristics, efficacy, safety, and economic impact of the TSOAs for thromboprophylaxis following THA, as well as the aspects of therapeutic monitoring and anticoagulation reversal in the event of bleeding complications or a need for urgent reversal.

Management of bleeding and reversal strategies for oral anticoagulants: clinical practice considerations

PURPOSE

Currently available clinical data and optimal strategies for reversing oral anticoagulants in patients who are bleeding or need an urgent invasive procedure or operation are reviewed.

SUMMARY

Bleeding from oral anticoagulants, including new target-specific oral agents (TSOAs), is a common cause of morbidity and mortality, especially in elderly patients. Limited clinical data are available to guide the reversal of warfarin or TSOAs in patients who are bleeding or need an urgent invasive procedure or operation. A panel of five experts with diverse backgrounds in anticoagulation therapy, cardiology, critical care, and emergency medicine and with experience in managing complications of anticoagulation therapy was convened to develop practical strategies for managing patients receiving oral anticoagulants who are bleeding or have an urgent need for an invasive procedure. The strategies were designed to guide clinicians in the acute care setting by providing efficient and potentially effective management concepts to avoid delays in initiating treatment that could adversely affect patient outcomes. The consensus of this expert panel is summarized herein. Recommendations are based on currently available evidence from a comprehensive review of the literature and other pertinent data, along with the experience and expert opinion of the panelists.

CONCLUSION

Bleeding is a serious complication of the use of oral anticoagulants, and limited information is available to guide the reversal of warfarin or TSOAs in patients who are bleeding or are in need of an urgent invasive procedure. Use of a systematic approach to assessing and treating these patients based on available evidence and expert opinion can help avoid delays that could adversely affect patient outcomes.

Beyond warfarin: a patient-centered approach to selecting novel oral anticoagulants for stroke prevention in atrial fibrillation

BACKGROUND

Warfarin reduces stroke in patients with atrial fibrillation. However, its narrow therapeutic index and need for chronic monitoring are barriers to its optimal utilization in many patients. The recent introduction of 3 novel oral anticoagulants (NOACs), as alternatives to warfarin, may change the eligibility and management of patients with nonvalvular atrial fibrillation (NVAF) who require systemic anticoagulation.

PURPOSE

To summarize contemporary indications for anticoagulation in NVAF, and to help provide patient-centered clinical decision making for selecting warfarin or 1 of the NOACs (dabigatran, rivaroxaban, apixaban) based on randomized trials and mechanistic data for each drug.

DATA SOURCES AND STUDY SELECTION

The primary clinical outcome trials of warfarin and the NOACs, pharmacologic studies, and briefing documents from the US Food and Drug Administration were reviewed.

DATA EXTRACTION AND DATA SYNTHESIS

In randomized trials, NOACs were consistently noninferior to warfarin for reducing stroke or systemic embolism in patients with NVAF, with reductions in intracranial bleeding as well. However, NOACs have several important drug-drug interactions, exclusion criteria for specific patient subgroups (eg, severe renal disease), and each medication may have a different impact on other clinical outcomes such as myocardial infarction or gastrointestinal bleeding. Benefits of the new drugs are particularly pronounced when international normalized ratio levels on warfarin are labile.

CONCLUSIONS

Warfarin continues to play an important role in the prevention of stroke or systemic embolism in NVAF. Among selected patients, the use of NOACs provides equal or superior benefit, without the need for chronic anticoagulation monitoring or ongoing dose titration.

Controversies regarding the new oral anticoagulants for stroke prevention in patients with atrial fibrillation

Increasing use of the new oral anticoagulants (NOACs) – dabigatran, rivaroxaban, and apixaban – has prompted considerable discussion in the medical community even as warfarin remains the mainstay of therapy. This article raises 10 controversial issues regarding the use of NOACs for stroke prevention in patients with atrial fibrillation, and offers a review of the latest available evidence. We provide a brief overview of the mechanism and dosing of these drugs, as well as a summary of the key clinical trials that have brought them into the spotlight. Comparative considerations relative to warfarin such as NOAC safety, efficacy, bleeding risk, reversibility, drug-transitioning and use in patients well controlled on warfarin are addressed. Use in select populations such as the elderly, those with coronary disease, renal impairment, or on multiple anti-platelet drugs is also discussed. Finally, we consider such specific issues as comparative efficacy, off-label use, cost, rebound and management during events. Ultimately, the rise of the NOACs to mainstream use will depend on further data and clinical experience amongst the medical community.

Reversal of target-specific oral anticoagulants

Target-specific oral anticoagulants (TSOACs) provide safe and effective anticoagulation for the prevention and treatment of thrombosis in a variety of clinical settings by interfering with the activity of thrombin (dabigatran) or factor Xa (rivaroxaban, apixaban, edoxaban, betrixaban). Although TSOACs have practical advantages over vitamin K antagonists (VKAs), there are currently no antidotes to reverse their anticoagulant effect. Herein we summarize the available evidence for TSOAC reversal using nonspecific and specific reversal agents. We discuss important limitations of existing evidence, which is derived from studies in human volunteers, animal models and in vitro experiments. Studies evaluating the safety and efficacy of reversal agents on clinical outcomes such as bleeding and mortality in patients with TSOAC-associated bleeding are needed.

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.

[Anticoagulation]

Anticoagulant drugs belong to the group of antithrombotic agents and are successfully used in the prophylaxis and treatment of thromboembolic disorders. The use of anticoagulants in the prevention of deep venous thrombosis has significantly lowered the risk of venous thrombosis and fatal pulmonary embolisms even in high-risk situations such as orthopedic surgery. Anticoagulants play a central role in the treatment of acute venous thrombosis and in the prevention of recurrent events. Long-term anticoagulation therapy with orally active anticoagulants significantly reduces the risk of thromboembolic complications in patients showing cardiac arrhythmias. Whereas a few years ago heparins and vitamin K antagonists were the dominant anticoagulants, today a wide range of anticoagulants with improved pharmacological profiles are available. It remains an open question whether these new anticoagulants will improve the efficacy, safety, and acceptance of anticoagulant treatment approaches.

Edoxaban

Vitamin K antagonists (VKAs) remain the standard therapy for anticoagulation in prevention and treatment of venous thromboembolism (VTE) and for the prevention of stroke in atrial fibrillation (AF). Due to numerous limitations of VKAs, target-specific oral anticoagulants have been developed. Edoxaban is a direct activated factor X inhibitor with attractive features among which are once daily dosing, no need for routine monitoring, and minimal drug–drug interactions. In patients undergoing orthopedic surgery, edoxaban was superior to enoxaparin in preventing VTE. Furthermore, a recent large-scale phase III trial in patients with symptomatic VTE demonstrated that edoxaban was noninferior to warfarin in preventing recurrent VTE and reduced bleeding. In the largest trial of anticoagulation in patients with AF to date, edoxaban was noninferior to warfarin in the prevention of stroke or systemic embolism and reduced bleeding and cardiovascular mortality. This review provides an overview of the pharmacology, clinical trial results, and potential indications for edoxaban.

Latest developments in anticoagulant drug discovery

Thromboembolic diseases have increased in number over the past years. Oral anticoagulants impair the formation and progression of thrombotic processes and are therefore of great importance in the treatment of these diseases. Until recently, vitamin K antagonists were used to block the coagulation system. But these agents display a lot of interactions besides their narrow therapeutic range and have potential risk of hemorrhage complications. Therefore, other factors of the coagulation cascade are currently being explored as therapeutic targets for the development of novel anticoagulants. This review will provide an overview of new drugs promising more effectiveness in the treatment of arterial and venous embolism. Furthermore, pharmacodynamics and drug interactions regarding new anticoagulants will be reported.

How I treat target-specific oral anticoagulant–associated bleeding

Target-specific oral anticoagulants (TSOACs) that directly inhibit thrombin (dabigatran) or factor Xa (rivaroxaban, apixaban) are effective and safe alternatives to vitamin K antagonists (VKAs) and low-molecular-weight heparin (LMWH). Although these agents have practical advantages compared with VKAs and LMWH, there are no antidotes that reverse their anticoagulant effect. Clinical evidence for the efficacy of nonspecific therapies that promote formation of fibrin (prothrombin complex concentrate [PCC], activated PCC [aPCC], and recombinant factor VIIa) in the setting of TSOAC-associated bleeding is lacking, and these prohemostatic products are associated with a risk of thrombosis. In the absence of specific antidotes, addition of PCC or aPCC to maximum supportive therapy may be reasonable for patients with severe or life-threatening TSOAC-associated bleeding. Targeted antidotes for these agents are in development.

Safety of new oral anticoagulant drugs: a perspective

The recent development of new oral anticoagulants (NOACs) offers the possibility of efficacy, relative safety and convenience compared with warfarin. This could lead to greater patient compliance, with easier management and improved provision of thromboprophylaxis. Safety whilst using NOACs should be focused on bleeding cases, surgery or on the management of patients receiving anticoagulant therapy with concomitant impairment of renal function, especially since many NOACs are dependent on renal excretion. Thus, if the clearance creatinine indicates severe renal impairment, NOACS will be contraindicated or their dose needs to be changed. In patients who need surgery, there are published protocols of management, depending on the severity of the intervention and renal function. In the case of severe hemorrhage, requiring rapid reversal of the anticoagulant effect and in the absence of specific antidotes, alternatives such as one of the nonspecific haemostatic agents must be considered. Clinical evaluation in bleeding situations and a meticulous risk-benefit appraisal for NOACs is needed, and these procoagulant agents and patients must be monitored closely. This article provides an overview of the pharmacology and potential risks, as well as the efficacy and safety of NOACs.

The pharmacokinetics of edoxaban for the prevention and treatment of venous thromboembolism

INTRODUCTION

Thromboembolic diseases will become the most important contributors to mortality and morbidity for modern societies. Current antithrombotic strategies using heparins or vitamin K antagonists are inconvenient, with limitations and inherent side effects. A series of new oral anticoagulants with powerful and reliable antithrombotic actions have been developed in the last decade.

AREAS COVERED

Edoxaban is a direct and specific inhibitor of activated factor X, delivered orally. This article reviews literature from PubMed and articles referenced within. The text explores the pharmacological aspects of its antithrombotic action. Pharmacokinetics, metabolism and drug interactions are examined. The review places the results of recent clinical trials that have evaluated the antithrombotic potential of edoxaban versus standard antithrombotic therapies in the prophylaxis and treatment of venous thromboembolism into perspective. The possible relationship between the pharmacokinetic profile of edoxaban and the favorable results in clinical trials is discussed.

EXPERT OPINION

Edoxaban is perceived as a major advance, compared to vitamin K antagonists, in the prevention and treatment of thromboembolic disease given its favorable efficacy, safety, pharmacokinetic profile and renal clearance. The results of ongoing large international trials exploring the prevention of thrombotic complications in patients in different clinical settings should ensure the approval of edoxaban to treat new indications.

Apixaban

Each month, subscribers to The Formulary Monograph Service receive 5 to 6 well-documented monographs on drugs that are newly released or are in late phase 3 trials. The monographs are targeted to Pharmacy & Therapeutics Committees. Subscribers also receive monthly 1-page summary monographs on agents that are useful for agendas and pharmacy/nursing in-services. A comprehensive target drug utilization evaluation/medication use evaluation (DUE/MUE) is also provided each month. With a subscription, the monographs are sent in print and are also available on-line. Monographs can be customized to meet the needs of a facility. A drug class review is now published monthly with The Formulary Monograph Service. Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. For more information about The Formulary Monograph Service, call The Formulary at 800-322-4349. The June 2013 monograph topics are dimethyl fumarate (BG-12) delayed-release capsules, canagliflozin, ospemifene, aripiprazole extended-release injectable, and dabrafenib. The DUE/MUE is on dimethyl fumarate.

Clinical research priorities in adult congenital heart disease

BACKGROUND

Adult congenital heart disease (ACHD) clinicians are hampered by the paucity of data to inform clinical decision-making. The objective of this study was to identify priorities for clinical research in ACHD.

METHODS

A list of 45 research questions was developed by the Alliance for Adult Research in Congenital Cardiology (AARCC), compiled into a survey, and administered to ACHD providers. Patient input was sought via the Adult Congenital Heart Association at community meetings and online forums. The 25 top questions were sent to ACHD providers worldwide via an online survey. Each question was ranked based on perceived priority and weighted based on time spent in ACHD care. The top 10 topics identified are presented and discussed.

RESULTS

The final online survey yielded 139 responses. Top priority questions related to tetralogy of Fallot (timing of pulmonary valve replacement and criteria for primary prevention ICDs), patients with systemic right ventricles (determining the optimal echocardiographic techniques for measuring right ventricular function, and indications for tricuspid valve replacement and primary prevention ICDs), and single ventricle/Fontan patients (role of pulmonary vasodilators, optimal anticoagulation, medical therapy for preservation of ventricular function, treatment for protein losing enteropathy). In addition, establishing criteria to refer ACHD patients for cardiac transplantation was deemed a priority.

CONCLUSIONS

The ACHD field is in need of prospective research to address fundamental clinical questions. It is hoped that this methodical consultation process will inform researchers and funding organizations about clinical research topics deemed to be of high priority.

Economic Implications of Inadequate Treatment of Venous Thromboembolism and Potential Solutions

Venous thromboembolism (VTE) is a common and serious medical complication among medical and surgical patients, both in the hospital and postdischarge. Patients with venous stasis or vascular damage or those with underlying hypercoagulable disorders, including cancer, are at risk of developing VTE. The clinical consequences of inadequate treatment of VTE can result in significant patient morbidity and mortality. The direct health care costs and indirect societal costs related to VTE and its complications are high. Traditional anticoagulants can reduce recurrent VTE but they present costly management challenges. Oral anticoagulants currently in development offer simpler management compared with the established agents, potentially resulting in improved adherence with VTE treatment regimens and better outcomes. Reductions in recurrent VTE and its associated complications could translate into reduced direct and indirect costs.

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.

A new era of stroke prevention in atrial fibrillation: comparing a new generation of oral anticoagulants with warfarin

Traditionally, warfarin has been used to prevent stroke in patients with atrial fibrillation (AF), but data from large, multinational, prospective, randomized studies suggest that novel oral anticoagulants (NOACs) may be suitable alternatives. These include the direct thrombin inhibitor dabigatran and the factor Xa inhibitors rivaroxaban, apixaban, and edoxaban. These data showed that dabigatran 150 mg twice daily was more effective at preventing stroke than warfarin, with similar rates of major bleeding, while rivaroxaban 20 mg once daily was noninferior to warfarin, with no difference in major bleeding rates. In addition, apixaban 5 mg twice daily was shown to be superior to warfarin for preventing stroke, with lower bleeding rates. Currently, edoxaban is still in clinical trials. NOACs offer more predictable anticoagulant effects than warfarin and do not require regular monitoring; however, different NOACs are associated with varied drug interactions and limitations related to use in certain patient populations. Overall, the clinical data suggest that these novel agents will offer new options for stroke prevention in patients with AF.

Novel Oral Anticoagulants: A Focused Review for Stroke Physicians

Novel oral anticoagulants provide an effective and convenient alternative to warfarin for stroke prevention in patients with atrial fibrillation. However, novel anticoagulants also present new challenges for stroke physicians, such as measurement of anticoagulant effect in emergency situations, use of thrombolysis in acute ischemic stroke, optimal timing of introduction of novel anticoagulants following acute ischemic stroke, and management of intracerebral hemorrhage. In this review, we propose pragmatic approaches to dealing with challenging management issues that will face stroke physicians who care for patients with acute stroke in the novel oral anticoagulant era.

A systematic update on the state of novel anticoagulants and a primer on reversal and bridging

BACKGROUND

Current prevention and treatment of venous thromboembolism (VTE) includes familiar agents that have been in use for many years, including unfractionated heparin, low-molecular-weight heparin (LMWH), and vitamin K antagonists (VKAs). A number of novel oral anticoagulants are currently developed or are in stages of development to either replace VKAs in concert with initial heparin or LMWH, or to replace both heparin/LMWH and VKAs totally as monotherapy. These agents hold the promise of not requiring monitoring, being safer in terms of bleeding risk than current agents, and being of equal or improved efficacy compared with established anticoagulants.

METHODS

In the following report, we systematically review the oral agents currently approved or closest to approval for both VTE and atrial fibrillation treatment, focusing on the treatment of VTE: dabigatran, rivaroxaban, and apixaban.

RESULTS

Findings of clinical use and comparisons to standard care of these agents are summarized in depth, by succinctly reviewing all major randomized controlled trials. Mechanistic and functional differences are reviewed, as Dabigatran targets activated factor II (factor IIa), while rivaroxaban and apixaban target activated factor X (factor Xa). We also discuss the inability at the present time to reliably reverse the anticoagulant effects of these agents, provide a suggested strategy for reversal, and finally discuss an approach to bridging these agents when other procedures are required while currently taking one of these three agents.

CONCLUSIONS

These agents, while still with many unanswered questions, demonstrate great promise in the prevention and treatment of VTE.

Reversal of novel oral anticoagulants in patients with major bleeding

Novel oral anticoagulants (NOACs) that directly inhibit thrombin (dabigatran) or factor Xa (rivaroxaban, apixaban, edoxaban) are effective therapies for the prevention and treatment of thromboembolism with reduced bleeding complications compared with warfarin for some indications. However, specific antidotes to reverse the anticoagulant activity of NOACs in the event of major bleeding are not available. Evidence supporting non-specific prohemostatic therapies (prothrombin complex concentrate [PCC], activated prothrombin complex concentrate [aPCC], recombinant factor VIIa) in this setting is limited to healthy human volunteers, animal models, and in vitro studies. Clinical outcome data are lacking. Administration of PCC or aPCC may be considered in addition to supportive measures for patients with severe or life-threatening bleeding. Clinical studies are needed to establish the efficacy and safety of these treatments. Target-specific antidotes are in development and hold promise for NOAC reversal, but require further investigation.

Anticoagulant therapy with the oral direct factor Xa inhibitors rivaroxaban, apixaban and edoxaban and the thrombin inhibitor dabigatran etexilate in patients with hepatic impairment

The direct factor Xa (FXa) inhibitors rivaroxaban, apixaban and edoxaban, and the thrombin inhibitor dabigatran etexilate (dabigatran) have gained approval for use in several indications, most notably for the prevention and treatment of venous thromboembolism (VTE) and for the prevention of stroke in patients with atrial fibrillation. Hepatic impairment can affect the disposition of these anticoagulants considerably not only because of the hepatic metabolism of the direct FXa inhibitors but also because moderate to severely impaired hepatic function will affect coagulation. This review describes the key pharmacological properties of novel oral anticoagulants with special attention to patients with impaired hepatic function. In subjects with moderately impaired liver function (i.e. Child-Pugh classification B), the area under the plasma concentration-time curve (AUC) of rivaroxaban (10 mg single dose) is increased by 2.27-fold, which is paralleled by an increase in FXa inhibition. The AUC of apixaban (5 mg single dose) is increased by 1.09-fold, whereas the AUC of edoxaban (15 mg single dose) is decreased by 4.8 % and the AUC of dabigatran (150 mg single dose) is decreased by 5.6 %. Specific labelling restrictions for rivaroxaban, apixaban and dabigatran regarding impaired hepatic function are based on both the Child-Pugh classification and liver-related exclusion criteria applied in pivotal clinical trials. Rivaroxaban is contraindicated in patients with hepatic disease associated with coagulopathy and clinically relevant bleeding risk, including cirrhotic patients classified as Child-Pugh B and C. Apixaban can be used with caution in patients with mild (Child-Pugh A) or moderate (Child-Pugh B) hepatic impairment or in patients with alanine aminotransferase and aspartate aminotransferase levels >2× upper limit of normal (ULN). Apixaban is not recommended in patients with severe hepatic impairment and is contraindicated in those with hepatic disease associated with coagulopathy and clinically relevant bleeding risk. Dabigatran is not recommended in patients with elevated liver enzymes (>2× ULN). Dabigatran is contraindicated in patients with hepatic impairment or liver disease expected to have any impact on survival. Currently, edoxaban is not available in the US or European markets. However, the Japanese label did not restrict use in hepatic dysfunction but advises care in patients with severe hepatic impairment.