Extended use of dabigatran, warfarin, or placebo in venous thromboembolism

Risk of drug-induced liver injury with the new oral anticoagulants: systematic review and meta-analysis

OBJECTIVE

In recent years, safety alerts have been made warning of the risk of serious drug-induced liver injury (DILI) caused by cardiovascular drugs. The new oral anticoagulants (NOACs) have now reached the market. However, safety concerns have been raised about their hepatic safety. Therefore we aimed to evaluate NOAC liver-related safety.

METHODS

Systematic review and meta-analysis of phase III randomised controlled trials (RCTs). Medline and CENTRAL were searched to September 2013. Reviews and reference lists were also searched. Two reviewers independently searched for studies and retrieved data estimates. Primary outcome was DILI (transaminases elevations >3× upper limit of normal (ULN) with total bilirubin >2× ULN). NOACs were compared against any control group. Random-effects meta-analysis was performed, and pooled estimates were expressed as relative risk (RR) and 95% CI heterogeneity was evaluated with I(2) test.

RESULTS

Twenty-nine RCTs evaluating 152 116 patients (mean follow-up of 16 months) were included. All RCTs were rated as having low risk of bias. NOAC were not associated with an increased risk of DILI (RR 0.90, 95% CI 0.72 to 1.13, I(2)=0%). Similar results were obtained for individual NOAC (rivaroxaban, apixaban, dabigatran, darexaban, edoxaban) and considering the different control groups (vitamin K antagonists, low molecular weight heparin (LMWH) and placebo). The risk of transaminases elevations (>3×ULN) was lower among NOAC-treated patients, in particular in comparison with LMWH-treated patients (RR 0.71, 95% CI 0.59 to 0.85; I(2)=27%)

CONCLUSIONS

NOACs are not associated with an increased risk of DILI. The unexpected 'protective' effect of NOAC is probably due to LMWH-associated hepatotoxicity.

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.

Venous thromboembolism in 2013: the advent of the novel oral anticoagulants

New findings published in 2013 strongly support the use of novel oral anticoagulants in the treatment of thromboembolic disorders. These drugs have been shown to have a more-favourable benefit-to-risk profile than older compounds, enabling their use from the start of treatment and in the whole spectrum of clinical presentations.

D-dimer levels over time and the risk of recurrent venous thromboembolism: an update of the Vienna prediction model

Background

Patients with unprovoked venous thromboembolism (VTE) can be stratified according to their recurrence risk based on their sex, the VTE location, and d‐dimer measured 3 weeks after anticoagulation by the Vienna Prediction Model. We aimed to expand the model to also assess the recurrence risk from later points on.

Methods and Results

Five hundred and fifty‐three patients with a first VTE were followed for a median of 68 months. We excluded patients with VTE provoked by a transient risk factor or female hormone intake, with a natural inhibitor deficiency, the lupus anticoagulant, or cancer. The study end point was recurrent VTE, which occurred in 150 patients. d‐Dimer levels did not substantially increase over time. Subdistribution hazard ratios (95% confidence intervals) dynamically changed from 2.43 (1.57 to 3.77) at 3 weeks to 2.27 (1.48 to 3.48), 1.98 (1.30 to 3.02) , and 1.73 (1.11 to 2.69) at 3, 9, and 15 months in men versus women, from 1.84 (1.00 to 3.43) to 1.68 (0.91 to 3.10), 1.49 (0.79 to 2.81) , and 1.44 (0.76 to 2.72) in patients with proximal deep vein thrombosis or pulmonary embolism compared with calf vein thrombosis, and from 1.30 (1.07 to 1.58) to 1.27 (1.06 to 1.51), 1.20 (1.02 to 1.41), and 1.13 (0.95 to 1.36) per doubling d‐dimer. Using a dynamic landmark competing risks regression approach, we generated nomograms and a web‐based calculator to calculate risk scores and recurrence rates from multiple times after anticoagulation.

Conclusions

Risk of recurrent VTE after discontinuation of anticoagulation can be predicted from multiple random time points by integrating the patient's sex, location of first VTE, and serial d‐dimer measurements.

Comparisons between novel oral anticoagulants and vitamin K antagonists in patients with CKD

Novel oral anticoagulants (NOACs) (rivaroxaban, dabigatran, apixaban) have been approved by international regulatory agencies to treat atrial fibrillation and venous thromboembolism in patients with kidney dysfunction. However, altered metabolism of these drugs in the setting of impaired kidney function may subject patients with CKD to alterations in their efficacy and a higher risk of bleeding. This article examined the efficacy and safety of the NOACs versus vitamin K antagonists (VKAs) for atrial fibrillation and venous thromboembolism in patients with CKD. A systematic review and meta-analyses of randomized controlled trials were conducted to estimate relative risk (RR) with 95% confidence interval (95% CIs) using a random-effects model. MEDLINE, Embase, and the Cochrane Library were searched to identify articles published up to March 2013. We selected published randomized controlled trials of NOACs compared with VKAs of at least 4 weeks' duration that enrolled patients with CKD (defined as creatinine clearance of 30-50 ml/min) and reported data on comparative efficacy and bleeding events. Eight randomized controlled trials were eligible. There was no significant difference in the primary efficacy outcomes of stroke and systemic thromboembolism (four trials, 9693 participants; RR, 0.64 [95% CI, 0.39 to 1.04]) and recurrent thromboembolism or thromboembolism-related death (four trials, 891 participants; RR, 0.97 [95% CI, 0.43 to 2.15]) with NOACs versus VKAs. The risk of major bleeding or the combined endpoint of major bleeding or clinically relevant nonmajor bleeding (primary safety outcome) (eight trials, 10,616 participants; RR 0.89 [95% CI, 0.68 to 1.16]) was similar between the groups. The use of NOACs in select patients with CKD demonstrates efficacy and safety similar to those with VKAs. Proactive postmarketing surveillance and further studies are pivotal to further define the rational use of these agents.

The risk of recurrent thromboembolic disorders in patients with unprovoked venous thromboembolism: new scenarios and opportunities

The risk of recurrent thromboembolic disorders in the 10-year period following an episode of unprovoked venous thromboembolism (VTE) ranges between 30 and 50%, the rate being higher in patients with primary deep venous thrombosis (DVT) than in those with primary pulmonary embolism (PE). The clinical presentation with primary PE increases by more than three times the risk of a new PE episode over that with isolated DVT. Baseline parameters that increase this risk are the proximal location of DVT, obesity, old age and male sex, whereas the role of thrombophilia is controversial. An increasing role is played by post-baseline parameters such as the ultrasound assessment of residual vein thrombosis and the determination of D-dimer. While the latest international guidelines suggest indefinite anticoagulation for most patients with the first episode of unprovoked VTE, new scenarios are being offered by the identification of risk stratification models and by strategies that have the potential to help identify patients in whom anticoagulation can be safely discontinued, such as those that incorporate the assessment of D-dimer and residual vein thrombosis. New opportunities are being offered by low-dose aspirin, which has recently been reported to decrease by more than 30% the risk of recurrent events without increasing the bleeding risk; and especially by a few emerging anti-Xa and anti-IIa oral compounds, which are likely to induce fewer haemorrhagic complications than vitamin K antagonists while preserving at least the same effectiveness, do not require laboratory monitoring, and can be used immediately after the thrombotic episode.

Advantages and limitations of the new anticoagulants

During recent years, three new anticoagulants (dabigatran, rivaroxaban and apixaban) have been introduced to the market, probably with one more anticoagulant (edoxaban) in the next 2 years. This review is not intended to compare the efficacy and risks of these new agents, but rather to detail the advantages and limitations. The pharmacokinetic characteristics of these drugs have few drug and food interactions, predictable dose responses, and rapid onset and offset, thus resulting in simplified management of the patient requiring anticoagulant therapy. No routine laboratory monitoring is required. A somewhat unexpected, but exciting observation involving the new anticoagulants, is the uniform reduction in intracranial bleeding by one-half compared with warfarin. The potential limitations of the new anticoagulants include uncertainty regarding assessment of drug levels, safe drug levels for major surgery, management of major bleeding, renal dependence, multiple dose regimens, adherence in the absence of frequent monitoring and unknown, rare side effects that were not captured in the trials. This review should clarify some of these concerns.

Major bleeding during secondary prevention of venous thromboembolism in patients who have completed anticoagulation: a systematic review and meta-analysis

BACKGROUND

The risk of major bleeding in patients who have completed anticoagulation therapy for unprovoked venous thromboembolism (VTE) is unknown.

OBJECTIVE

To report the major bleeding and fatal bleeding rates in patients randomized to placebo or observation (i.e. no anticoagulation therapy) for the secondary prevention of recurrent VTE.

PATIENTS AND METHODS

We performed a systematic review and meta-analysis of the literature to summarize the rates of major bleeding and fatal bleeding in patients randomized to placebo or observation during the secondary prevention of VTE. Unrestricted searches of MEDLINE (January 1, 1950 to August 31, 2013), Embase (January 1, 1980 to August 31, 2013), and the Cochrane Register of Controlled Trials using the OVID interface were conducted. Publications from potentially relevant journals were also searched by hand. We used a random-effects model to pool study results and I(2) testing to assess for heterogeneity.

RESULTS

The analysis included 11 studies and 3965 patients who were followed for a median of 24 months. The overall pooled major bleeding rate was 0.45 per 100 patient-years (95% CI 0.29-0.64, I(2) = 0%), and the overall pooled fatal bleeding rate was 0.14 per 100 patient-years (95% CI 0.057-0.26, I(2) = 0%).

CONCLUSIONS

Patients not receiving anticoagulant therapy for the secondary prevention of VTE experience major bleeding events, and this may have an impact on recommendations for extended treatment in this patient population.

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.

Effectiveness and safety of novel oral anticoagulants as compared with vitamin K antagonists in the treatment of acute symptomatic venous thromboembolism: a systematic review and meta-analysis

INTRODUCTION

New direct oral anticoagulants (NOACs) constitute a novel treatment option for acute venous thromboembolism (VTE), with practical advantages. Individual studies have demonstrated comparable efficacy to that of vitamin K antagonists (VKAs) and have suggested a more favorable safety profile . We performed a meta-analysis to determine the efficacy and safety of NOACs as compared with those of VKAs in patients with acute VTE.

METHODS

We searched MEDLINE, EMBASE, the Cochrane Database of Systematic Reviews and the Clinical Trials Registry up to October 2013. Eligible studies included phase 3 trials comparing NOACs with VKAs in patients with acute VTE. Relative risks (RRs), absolute risk differences and numbers needed to treat (NNTs) to prevent one event were calculated for recurrent VTE, fatal pulmonary embolism (PE), overall mortality, major bleeding, and other bleeding complications, with random-effects models.

RESULTS

Five studies were included, investigating four NOACs (rivaroxaban, dabigatran, apixaban, and edoxaban) in 24 455 patients with acute VTE. RRs for recurrent VTE, fatal PE and overall mortality for NOACs vs. VKAs were 0.88 (95% confidence interval [CI] 0.74-1.05), 1.02 (95% CI 0.39-5.96), and 0.97 (95% CI 0.83-1.14), respectively. The RR for major bleeding was 0.60 (95% CI 0.41-0.88). The NNT with NOACs instead of VKA to prevent one major bleed was 149. The RR and NNT for fatal bleeding were 0.36 (95% CI 0.15-0.87) and 1111. A fixed-effect network analysis did not demonstrate significant differences between individual NOACs and rivaroxaban.

CONCLUSIONS

NOACs have comparable efficacy to that of VKAs, and are associated with a significantly lower risk of bleeding complications, although the NNT to prevent one major bleed was relatively high.

Consistency of safety profile of new oral anticoagulants in patients with renal failure

BACKGROUND

The use of new oral anticoagulants (NOACs) in patients with impaired renal function has raised major concerns, in particular the possibility of an increased risk of bleeding due to accumulation. The aims of this work were to assess the safety of NOACs in patients with renal failure and describe the relationship between clinical events and drug renal excretion magnitude.

METHODS

All phase III trials comparing NOACs with vitamin K antagonists (VKAs) in patients with estimated glomerular filtration (eGFR) rate < 50 mL min(-1) were eligible. The main safety and efficacy outcomes were major bleeding and thrombosis. A meta-regression was performed to estimate the correlation between the treatment effect estimate and the percentage of renal excretion.

RESULTS

Nine studies (12 272 patients) were included. A significantly greater relative reduction in major bleeding was seen for NOACs with renal excretion <50% (RR, 0.61; CI, 0.51-0.74) than for those with high renal excretion (RR, 0.96; CI, 0.85-1.07) (interaction test, P < 0.0001). A linear relationship between the relative risk of major bleeding and the magnitude of renal excretion was found by meta-regression (R(2)  = 0.66, P = 0.03). For thrombosis, a greater treatment effect of NOA vs. INR-adjusted VKA was observed in patients with eGFR < 50 mL min(-1) (RR 0.78, CI 0.67-0.92), but no correlation between treatment effect and renal excretion was found.

CONCLUSIONS

New oral anticoagulants were at least as effective as VKAs, with reduced risks of major bleeding and thrombosis in patients with eGFR < 50 mL min(-1) . The renal excretion of these new drugs seemed to modify the safety profile, contrary to the efficacy.

Treatment of acute venous thromboembolism with dabigatran or warfarin and pooled analysis

BACKGROUND

Dabigatran and warfarin have been compared for the treatment of acute venous thromboembolism (VTE) in a previous trial. We undertook this study to extend those findings.

METHODS AND RESULTS

In a randomized, double-blind, double-dummy trial of 2589 patients with acute VTE treated with low-molecular-weight or unfractionated heparin for 5 to 11 days, we compared dabigatran 150 mg twice daily with warfarin. The primary outcome, recurrent symptomatic, objectively confirmed VTE and related deaths during 6 months of treatment occurred in 30 of the 1279 dabigatran patients (2.3%) compared with 28 of the 1289 warfarin patients (2.2%; hazard ratio, 1.08; 95% confidence interval [CI], 0.64-1.80; absolute risk difference, 0.2%; 95% CI, -1.0 to 1.3; P<0.001 for the prespecified noninferiority margin for both criteria). The safety end point, major bleeding, occurred in 15 patients receiving dabigatran (1.2%) and in 22 receiving warfarin (1.7%; hazard ratio, 0.69; 95% CI, 0.36-1.32). Any bleeding occurred in 200 dabigatran (15.6%) and 285 warfarin (22.1%; hazard ratio, 0.67; 95% CI, 0.56-0.81) patients. Deaths, adverse events, and acute coronary syndromes were similar in both groups. Pooled analysis of this study RE-COVER II and the RE-COVER trial gave hazard ratios for recurrent VTE of 1.09 (95% CI, 0.76-1.57), for major bleeding of 0.73 (95% CI, 0.48-1.11), and for any bleeding of 0.70 (95% CI, 0.61-0.79).

CONCLUSION

Dabigatran has similar effects on VTE recurrence and a lower risk of bleeding compared with warfarin for the treatment of acute VTE.

CLINICAL TRIAL REGISTRATION URL

www.clinicaltrials.gov. Unique identifiers: NCT00680186 and NCT00291330.

Meta-analysis of randomized controlled trials on risk of myocardial infarction from the use of oral direct thrombin inhibitors

Dabigatran has been associated with greater risk of myocardial infarction (MI) than warfarin. It is unknown whether the increased risk is unique to dabigatran, an adverse effect shared by other oral direct thrombin inhibitors (DTIs), or the result of a protective effect of warfarin against MI. To address these questions, we systematically searched MEDLINE and performed a meta-analysis on randomized trials that compared oral DTIs with warfarin for any indication with end point of MIs after randomization. We furthermore performed a secondary meta-analysis on atrial fibrillation stroke prevention trials with alternative anticoagulants compared with warfarin with end point of MIs after randomization. A total of 11 trials (39,357 patients) that compared warfarin to DTIs (dabigatran, ximelagatran, and AZD0837) were identified. In these trials, patients treated with oral DTIs were more likely to experience an MI than their counterparts treated with warfarin (285 of 23,333 vs 133 of 16,024, odds ratio 1.35, 95% confidence interval 1.10 to 1.66, p = 0.005). For secondary analysis, 8 studies (69,615 patients) were identified that compared warfarin with alternative anticoagulant including factor Xa inhibitors, DTIs, aspirin, and clopidogrel. There was no significant advantage in the rate of MIs with the use of warfarin versus comparators (odds ratio 1.06, 95% confidence interval 0.85 to 1.34, p = 0.59). In conclusion, our data suggest that oral DTIs were associated with increased risk of MI. This increased risk appears to be a class effect of these agents, not a specific phenomenon unique to dabigatran or protective effect of warfarin. These findings support the need for enhanced postmarket surveillance of oral DTIs and other novel agents.

Risk assessment for recurrence and optimal agents for extended treatment of venous thromboembolism

Venous thromboembolism (VTE) has a variable recurrence rate after the discontinuation of anticoagulant treatment. Therefore, the duration of anticoagulation therapy after a first VTE should be tailored to the estimated risk for recurrence. Anticoagulant therapy should be discontinued after the initial 3 to 6 months in those patients who had the first episode in association with temporary risk factors. The duration of anticoagulant therapy in patients who had a first episode of cancer-associated VTE should be reassessed over time based on the persistence of cancer and anticancer therapy. After 3 to 6 months of anticoagulant treatment for VTE, patients with a first unprovoked event and an estimated low risk for bleeding complications should be evaluated for indefinite treatment on an individualized basis. New oral anticoagulants have been evaluated for the extended treatment of VTE. Large phase 3 studies have shown that dabigatran, rivaroxaban, and apixaban are effective and safe in this indication. These agents do not require monitoring for dose adjustment and could make extended treatment more feasible and acceptable to patients.

New oral anticoagulants: their role and future

After 60 years in which warfarin has been the only practical oral anticoagulant, a number of new oral anticoagulants are entering practice. These drugs differ in a several important respects from warfarin; most notably they have a reliable dose-response effect which means they can be given without the need for monitoring. Their simpler metabolism and mode of action also results in fewer interactions with other drugs and with diet. However, some of their other properties such as renal clearance (to varying degrees), short half-life and lack of an available antidote may slow their rate of introduction. Large trials have established their non-inferiority to warfarin in a number of indications and in some cases their superiority. To date they have been licensed for prophylaxis following high risk orthopaedic procedures, non-valvular atrial fibrillation and treatment of venous thromboembolism, but is not clear that they will supplant warfarin in all areas.

Treatment with novel oral anticoagulants: indications, efficacy and risks

PURPOSE OF REVIEW

To summarize data relevant to novel oral anticoagulants (nOACs), mainly apixaban, dabigatran and rivaroxaban, as alternatives to vitamin K antagonists (VKAs).

RECENT FINDINGS

RE-LY was the first contemporaneous study to compare a nOAC, dabigatran, with dose-adjusted warfarin, for prevention of stroke and systemic embolism in atrial fibrillation. Since then multiple studies have compared nOACs to warfarin for acute (RE-COVER, RECOVER-II, EINSTEIN-DVT and EINSTEIN-PE) and extended treatment of venous thromboembolism (VTE) (AMPLIFY-EXT, RE-MEDY and RE-SONATE). Additional studies have examined stroke prevention in atrial fibrillation (ARISTOTLE and ROCKET-AF). We do not examine, in depth, use of nOACs in coronary artery disease.

SUMMARY

nOACs are an acceptable alternative to VKAs in certain situations - these are at least as effective as warfarin for secondary prevention of VTE and for prevention of stroke and systemic embolism in patients with atrial fibrillation. These compare favorably with warfarin with respect to their rate of fatal and major bleeding. However, special attention should be given when using these drugs in certain patient populations, in particular in patients with renal insufficiency, those receiving additional antithrombotic therapy, those with questionable compliance, patients of child bearing potential and those with a high risk of gastrointestinal bleeding.

Novel oral anticoagulants for the prevention and treatment of thromboembolism

Over the last 5 years, new oral anticoagulant options, including dabigatran, rivaroxaban and apixaban, have become available. Prior to this, vitamin K antagonists were the sole oral anticoagulants, which have been in use for more than 60 years. These novel agents have been studied in a variety of patient populations, including atrial fibrillation, acute coronary syndrome, treatment of venous thromboembolism and thromboprophylaxis. Compared with standard care, these agents have largely been found to be noninferior or superior for efficacy end points, with similar or improved rates of bleeding. As a result, these agents have become attractive alternatives to vitamin K antagonists for the prevention and treatment of thromboembolic disease. This article provides a summary of clinical trial data to help clinicians determine which agent is most appropriate for a given patient.

Management of dabigatran-induced bleeding: expert statement

The interdisciplinary group of experts has compiled a clinical guidance for manifest dabigatran-induced haemorrhage and envisaged invasive interventions on patients under dabigatran. It recommends an escalation of treatment measures as summarized in a pocket guide (see electronic supplementary material online and insert in the print issue).

Update on pharmacologic therapy for pulmonary embolism

Warfarin, unfractionated heparin (UFH), and low-molecular-weight heparins are anticoagulants that have been used for treatment of pulmonary embolism. Currently approved drugs for treatment of venous thromboembolism include UFH, enoxaparin, dalteparin, fondaparinux, warfarin, and rivaroxaban. The advent of newer oral anticoagulants such as rivaroxaban, dabigatran, and apixaban has provided us with alternative therapeutic options for long-term anticoagulation. This article will give an overview of the various anticoagulant drugs, use in various clinical scenarios, data supporting their clinical use, and recommendations regarding duration of anticoagulant therapy.

Reversing the new oral anticoagulants with prothrombin complex concentrates (PCCs): what is the evidence?

Newer oral anticoagulants offer several advantages over traditional agents (e.g. warfarin), but they are still associated with a bleeding risk and currently there is no validated reversal treatment for them. While there is little support for the use of fresh frozen plasma, and limited data available on the effects of activated recombinant factor VII, preclinical data suggest that prothrombin complex concentrates (PCCs) may have potential in this setting. PCCs are currently used to successfully reverse warfarin-induced anticoagulation; however, clinical evidence for their use with new oral anticoagulants is lacking, with most of the available data coming from preclinical animal studies. Furthermore, there appears to be variation in the ability of different PCCs to reverse the coagulopathy induced by the new anticoagulants, and a lack of correlation between the reversal of laboratory test results and the reversal of anticoagulant-induced bleeding. Although there have been encouraging results, care must be taken in generalising findings from animal models and nonbleeding human subjects to the situation in bleeding patients. Ultimately, more evidence supporting anticoagulation reversal for new anticoagulants is needed, particularly regarding the treatment of bleeding in human patients in a clinical setting. According to the current evidence, use of PCCs may be considered a reasonable approach in dire clinical situations; however, a consensus has not yet been reached regarding PCC use or dosing, due to lack of clinical data.

Treatment of cancer-associated thrombosis

Therapeutic options for the management of venous thromboembolism (VTE) in patients with cancer remain very limited. Although low-molecular-weight heparin monotherapy has been identified as a simple and efficacious regimen compared with an initial parenteral anticoagulant followed by long-term therapy with a vitamin K antagonist, many clinical questions remain unanswered. These include optimal duration of anticoagulant therapy, treatment of recurrent VTE, and the treatment of patients with concurrent bleeding or those with a high risk of bleeding. Treatment recommendations from consensus clinical guidelines are largely based on retrospective reports or extrapolated data from the noncancer population with VTE, as randomized controlled trials focused on cancer-associated thrombosis are sorely lacking. Furthermore, with improvements in imaging technology and extended survival duration of patients with cancer, we are encountering more unique challenges, such as the management of incidental VTE. Clinicians should be aware of the limitations of the novel oral anticoagulants and avoid the use of these agents because of the paucity of evidence in the treatment of cancer-associated thrombosis.

New oral anticoagulants--a review

BACKGROUND

Dabigatran, rivaroxaban and apixaban are three new oral anticoagulants that have recently been approved in Norway. The aim of this article is to provide an overview of the mechanisms of action, the most important indications and practical advice on the use of these drugs.

METHOD

The review is based on published phase 3 studies, a literature search in PubMed and the authors' clinical experience.

RESULTS

Indications for use of the new anticoagulants include thromboprophylaxis after total hip and knee replacement surgery (all three), prevention of stroke and systemic embolism in non-valvular atrial fibrillation (all three), treatment of acute venous thrombosis and secondary prophylaxis after venous thrombosis (currently only rivaroxaban). For the aforementioned indications, these drugs have proven to be non-inferior to standard established anticoagulation therapy. For atrial fibrillation, all three drugs have also shown a lower incidence of intracranial bleeding compared with standard treatment.

INTERPRETATION

It is important to limit the use of these drugs to approved indications, to select patients who show good compliance, to rule out contraindications and to identify drug interactions. Monitoring of coagulation is not required, but patients should be followed up regularly to detect conditions that may lead to changes in the expected efficacy or safety.

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.

Management and outcomes of major bleeding during treatment with dabigatran or warfarin

BACKGROUND

The aim of this study was to compare the management and prognosis of major bleeding in patients treated with dabigatran or warfarin.

METHODS AND RESULTS

Two independent investigators reviewed bleeding reports from 1034 individuals with 1121 major bleeds enrolled in 5 phase III trials comparing dabigatran with warfarin in 27 419 patients treated for 6 to 36 months. Patients with major bleeds on dabigatran (n=627 of 16 755) were older, had lower creatinine clearance, and more frequently used aspirin or non-steroid anti-inflammatory agents than those on warfarin (n=407 of 10 002). The 30-day mortality after the first major bleed tended to be lower in the dabigatran group (9.1%) than in the warfarin group (13.0%; pooled odds ratio, 0.68; 95% confidence interval, 0.46-1.01; P=0.057). After adjustment for sex, age, weight, renal function, and concomitant antithrombotic therapy, the pooled odds ratio for 30-day mortality with dabigatran versus warfarin was 0.66 (95% confidence interval, 0.44-1.00; P=0.051). Major bleeds in dabigatran patients were more frequently treated with blood transfusions (423/696, 61%) than bleeds in warfarin patients (175/425, 42%; P<0.001) but less frequently with plasma (dabigatran, 19.8%; warfarin, 30.2%; P<0.001). Patients who experienced a bleed had shorter stays in the intensive care unit if they had previously received dabigatran (mean 1.6 nights) compared with those who had received warfarin (mean 2.7 nights; P=0.01).

CONCLUSIONS

Patients who experienced major bleeding on dabigatran required more red cell transfusions but received less plasma, required a shorter stay in intensive care, and had a trend to lower mortality compared with those who had major bleeding on warfarin.

CLINICAL TRIAL REGISTRATION URL

http://www.ClinicalTrials.gov. Unique identifiers: NCT00262600, NCT00291330, NCT00680186, NCT00329238 and NCT00558259.

Respiratory review of 2013: pulmonary thromboembolism

Pulmonary embolism (PE), which can originate as a consequence of deep vein thrombosis (DVT), is the most frequent and potentially fatal venous thromboembolic event. Despite the fact that the incidence of venous thromboembolism (VTE) in Asians is lower than that in the Western populations, a recent epidemiologic study demonstrates an increasing incidence of VTE in the Korean population. Anticoagulants, including low molecular weight heparin (LMWH) and vitamin K antagonist (VKAs), have been the main treatments for PE, however, recently new oral anticoagulants (NOACs) were introduced. We will review how well patients with PE can be managed with the existing anticoagulants and NOACs along with the time span of treatment, which still pose some challenges for clinicians.

Practical Issues to Prevent Stroke Associated with Non-valvular Atrial Fibrillation

Stroke associated with non-valvular atrial fibrillation (NVAF) is one of the most important subtypes of ischemic stroke, and its importance is becoming even more apparent in an aging population. To assess the risk of stroke associated with NVAF, the CHADS2 and CHA2DS2-VASc scores are mainly used. Such scores can be used to predict the recurrence and prognosis of ischemic stroke. In addition, new oral anticoagulants (NOACs) and devices are being evaluated in the prevention of stroke associated with NVAF in addition to treatment with the conventional oral anticoagulant, warfarin. Since clinical experience with NOACs is not globally sufficient, a cautious approach is needed.

Oral rivaroxaban versus standard therapy for the treatment of symptomatic venous thromboembolism: a pooled analysis of the EINSTEIN-DVT and PE randomized studies

BACKGROUND

Standard treatment for venous thromboembolism (VTE) consists of a heparin combined with vitamin K antagonists. Direct oral anticoagulants have been investigated for acute and extended treatment of symptomatic VTE; their use could avoid parenteral treatment and/or laboratory monitoring of anticoagulant effects.

METHODS

A prespecified pooled analysis of the EINSTEIN-DVT and EINSTEIN-PE studies compared the efficacy and safety of rivaroxaban (15 mg twice-daily for 21 days, followed by 20 mg once-daily) with standard-therapy (enoxaparin 1.0 mg/kg twice-daily and warfarin or acenocoumarol). Patients were treated for 3, 6, or 12 months and followed for suspected recurrent VTE and bleeding. The prespecified noninferiority margin was 1.75.

RESULTS

A total of 8282 patients were enrolled; 4151 received rivaroxaban and 4131 received standard-therapy. The primary efficacy outcome occurred in 86 (2.1%) rivaroxaban-treated patients compared with 95 (2.3%) standard-therapy-treated patients (hazard ratio, 0.89; 95% confidence interval [CI], 0.66-1.19; pnoninferiority < 0.001). Major bleeding was observed in 40 (1.0%) and 72 (1.7%) patients in the rivaroxaban and standard-therapy groups, respectively (hazard ratio, 0.54; 95% CI, 0.37-0.79; p = 0.002). In key subgroups, including fragile patients, cancer patients, patients presenting with large clots, and those with a history of recurrent VTE, the efficacy and safety of rivaroxaban were similar compared with standard-therapy.

CONCLUSION

The single-drug approach with rivaroxaban resulted in similar efficacy to standard-therapy and was associated with a significantly lower rate of major bleeding. Efficacy and safety results were consistent among key patient subgroups.

TRIAL REGISTRATION EINSTEIN-PE

ClinicalTrials.gov, NCT00439777; EINSTEIN-DVT: ClinicalTrials.gov, NCT00440193.

Practical Management of Rivaroxaban for the Treatment of Venous Thromboembolism

Traditional anticoagulants, such as low-molecular-weight heparin and vitamin K antagonists, have been the mainstay for the treatment of venous thromboembolism (VTE) in the hospital setting and after discharge. These anticoagulants are effective but are associated with some limitations that may lead to their underuse. Based on the results of the EINSTEIN clinical trial program, the oral, direct factor Xa inhibitor rivaroxaban is approved for the treatment of acute deep vein thrombosis (DVT) and pulmonary embolism (PE) and for the prevention of recurrent VTE. The single-drug approach with rivaroxaban is now available in both the hospital and the outpatient settings and may overcome some of the limitations of traditional agents. This review provides hospital physicians with an overview of the practical management of rivaroxaban and a critical evaluation of its use for the treatment of DVT and PE, including in specific clinical settings and special patient populations.

Top practice-changing articles over the last two years

The field of thromboembolic disease and anticoagulation has had critical advances since the Anticoagulation Forum last met (May of 2011). We summarize our "top ten list" of papers that are likely to change the care of the anticoagulated population and improve their outcomes: (1) Patient self-management of their vitamin K antagonist and self monitoring can decrease thromboembolic events; (2) restarting warfarin after gastrointestinal bleeding may decrease mortality; (3) rivaroxaban is effective in the treatment of pulmonary embolism; either (4) apixaban or (5) low-dose aspirin prevented recurrent venous thromboembolic disease after a standard course of therapy; (6) warfarin prevents thrombotic complications up to at least 90 days after bioprosthetic aortic valve replacement; (7) the relative risk reduction of apixaban compared to warfarin is similar across CHADS2 scores, but the absolute risk reduction is higher in high-risk patients; (8) adherence to a warfarin dose-adjustment algorithm improved time in the therapeutic range and thromboembolic outcomes in the RE-LY trial; (9) warfarin had little benefit (if any) over aspirin in patients with decreased ejection fraction and sinus rhythm; (10) adding clopidogrel to aspirin in patients with lacunar infarcts did not reduce the risk of recurrent stroke and increased bleeding.

Efficacy and safety outcomes of oral anticoagulants and antiplatelet drugs in the secondary prevention of venous thromboembolism: systematic review and network meta-analysis

OBJECTIVE

To summarise and compare the efficacy and safety of various oral anticoagulants (dabigatran, rivaroxaban, apixaban, and vitamin K antagonists) and antiplatelet agents (acetylsalicylic acid) for the secondary prevention of venous thromboembolism.

DESIGN

Systematic review and network meta-analysis.

DATA SOURCES

Literature search using Medline (1950 to present), Embase (1980 to present), and the Cochrane Register of Controlled Trials using the OVID interface. Publications from potentially relevant journals were also searched by hand.

REVIEW METHODS

Randomised controlled trials of patients receiving anticoagulants, antiplatelet drugs, or placebo or observation for secondary prevention of venous thromboembolism. Selected outcomes were rates of recurrent venous thromboembolism and major bleeding. Two reviewers independently extracted data onto standardised forms.

RESULTS

12 articles met our inclusion criteria, with 11,999 patients evaluated for efficacy and 12,167 for safety. All treatments reduced the risk of recurrent venous thromboembolism. Compared with placebo or observation, vitamin K antagonists at a standard adjusted dose (target international normalised ratio 2.0-3.0) showed the highest risk difference (odds ratio 0.07; 95% credible interval 0.03 to 0.15) and acetylsalicylic acid showed the lowest risk difference (0.65; 0.39 to 1.03). Risk of major bleeding was higher with a standard adjusted dose of vitamin K antagonists (5.24; 1.78 to 18.25) than with placebo or observation. Fatal recurrent venous thromboembolism and fatal bleeding were rare. Detailed subgroup and individual patient level data were not available.

CONCLUSIONS

All oral anticoagulants and antiplatelet agents investigated in this analysis were associated with a reduced recurrence of venous thromboembolism compared with placebo or observation, although acetylsalicylic acid was associated with the lowest risk reduction. Vitamin K antagonists given at a standard adjusted dose was associated with the greatest risk reduction in recurrent venous thromboembolism, but also the greatest risk of major bleeding.

Assessment of anticoagulation intensity and management of bleeding with old and new oral anticoagulants

Warfarin is effective for the prevention and treatment of thromboembolism but produces variable anticoagulant effects and requires routine monitoring of the international normalized ratio (INR) to optimize the balance between efficacy and safety. The new oral anticoagulants (NOACs) have a more predictable anticoagulant effect and were recently demonstrated to be at least as efficacious and safe as warfarin despite being administered in fixed doses without routine coagulation monitoring. Specific laboratory tests have been developed to measure the anticoagulant effect of the NOACs but are not yet widely available, and the relation between drug levels and both coagulation test results and outcomes is uncertain. It remains to be demonstrated whether adjustment of the dose of NOACs, according to the results of laboratory testing, may lead to even greater efficacy and safety. The principles of bleeding management in patients treated with NOACs compared with patients receiving warfarin are similar. Most patients can be safely managed by interrupting drug treatment, performing local measures to stem the bleeding, and providing transfusion support as required. In patients with major or life-threatening bleeding and those requiring surgery, the anticoagulant effects of warfarin can be reversed using oral or intravenous vitamin K, fresh frozen plasma (FFP), and prothrombin complex concentrates (PCCs). Specific antidotes are under development for the NOACs but are not yet approved for clinical use. PCCs and recombinant factor VIIa may improve hemostasis in patients in whom bleeding develops during treatment with a NOAC, but their efficacy is unproven.

Novel antiplatelet and anticoagulant agents in the cardiac care unit

This article reviews the pivotal studies of several novel antiplatelet (prasugrel and ticagrelor) and anticoagulant (dabigatran, rivaroxaban, and apixaban) agents. The clinical use of these drugs in cardiac intensive care is discussed, focusing on the management of acute coronary syndromes, ischemic stroke, atrial fibrillation, and venous thromboembolism.

Targeting platelet thrombin receptor signaling to prevent thrombosis

Platelets contribute fundamentally to ischemic heart disease, and antiplatelet therapy has been critical to reducing acute thrombotic complications of atherosclerotic disease. Thrombin, by acting on protease activated receptors (PAR), is one of the most potent platelet activators. PAR-1 antagonists may therefore provide more comprehensive antithrombotic effects. We review the pathophysiology of atherothrombosis, platelet activation by thrombin, the role of platelet protease activated receptors (PAR), and the clinical data supporting their use.

Do novel oral anticoagulants do better than standard therapy in the treatment of deep vein thrombosis?

The focus of DVT treatment is the prevention of recurrence and thrombus migration by treatment with anticoagulants. The aim is to improve outcomes by reducing clot burden and by preventing thrombus propagation, in order to prevent PE and the development of long-term complication. Actually, initial therapy is parenteral anticoagulation, mainly with low molecular weight heparin followed by a vitamin K antagonist (VKA) for triggered and idiopathic DVT. The long term treatment suggestion with a VKA is for sure the most challenging therapeutic scenario, showing all the disadvantages of VKA especially in the onset phase when therapeutic levels of VKA are difficult to achieve. The difference between VKAs and NOACs is the fact, that NOACs target a specific factor in the coagulation cascade. At time now two pathways have been chosen for treatment options, the direct inhibition of active sites of thrombin and factor Xa. Routine monitoring is not required and the drugs can be administered in fixed doses, which should increase patient adherence to long term treatment. At time now, four novel anticoagulants are called to be options for DVT treatment. Rivaroxaban, apixaban and edoxaban are direct FXa inhibitors, whereas dabigtran etexilate is a direct thrombin inhibitor.