Review of Recently Approved Alternatives to Anticoagulation with Warfarin for Emergency Clinicians

Background

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

Objectives

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

Discussion

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

Conclusion

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

达比加群酯用于非瓣膜性房颤抗凝治疗的不良反应分析

目的:了解我院达比加群酯致药品不良反应发生的规律和特点,为临床安全合理使用达比加群酯提供参考依据.方法:采用回顾性分析方法,对我院2015年2月-2019年12月上报国家ADR监测中心的19例达比加群酯ADR报告进行统计分析.结果:19例达比加群酯ADR报告中,男女比例为1:1.7;61～70岁患者最多(42.11％)...     

Personalizing oral anticoagulant treatment in patients with atrial fibrillation

For decades, warfarin has remained the standard oral anticoagulation for stroke prevention in atrial fibrillation (AF). Three novel oral anticoagulants (NOACs) have been recently approved for stroke prevention in non-valvular AF: dabigatran, rivaroxaban and apixaban. Better pharmacological and clinical profiles make these newcomers a preferable alternative over warfarin. Current AF guidelines do not endorse NOACs over warfarin, or one NOAC over another. Indeed, choice of the anticoagulation regimen should be personalized based on the relative efficacy and safety of different agents across subgroups stratified by thrombotic and bleeding risk, as well as on other clinical factors, including anticoagulation control on warfarin, drug interactions, compliance and need for coagulation monitoring. This review appraises i) the randomized evidence on approved NOACs versus warfarin in AF across subgroups stratified by risk factors of stroke and bleeding and by the anticoagulation level reached on warfarin; and ii) clinical factors impacting on the anticoagulation regimen selection.     

Insights from the dabigatran versus warfarin trial in patients with venous thromboembolism (the RE-COVER trial)

In this clinical trial evaluation, we revisit the RE-COVER study, a large multicenter, randomized, double-blind, noninferiority trial on patients with acute venous thromboembolism treated with dabigatran versus warfarin. Study design and key results are re-evaluated in the context of previous work and future perspectives.     

Laboratory testing in patients treated with direct oral anticoagulants: a practical guide for clinicians

Click to hear Dr Baglin's perspective on the role of the laboratory in treatment with new oral anticoagulants

Summary

One of the key benefits of the direct oral anticoagulants (DOACs) is that they do not require routine laboratory monitoring. Nevertheless, assessment of DOAC exposure and anticoagulant effects may become useful in various clinical scenarios. The five approved DOACs (apixaban, betrixaban, dabigatran etexilate, edoxaban and rivaroxaban) have different characteristics impacting assay selection and the interpretation of results. This article provides an updated overview on (i) which test to use (and their advantages and limitations), (ii) when to assay DOAC levels, (iii) how to interpret the results relating to bleeding risk, emergency situations and perioperative management, and (iv) what is the impact of DOACs on routine and specialized coagulation assays. Assays for anti‐Xa or anti‐IIa activity are the preferred methods when quantitative information is useful, although the situations in which to test for DOAC levels are still debated. Different reagent sensitivities and variabilities in laboratory calibrations impact assay results. International calibration standards for all specific tests for each DOAC are needed to reduce the inter‐laboratory variability and allow inter‐study comparisons. The impact of the DOACs on hemostasis testing may cause false‐positive or false‐negative results; however, these can be minimized by using specific assays and collecting blood samples at trough concentrations. Finally, prospective clinical trials are needed to validate the safety and efficacy of proposed laboratory thresholds in relation to clinical decisions. We offer recommendations on the tests to use for measuring DOACs and practical guidance on laboratory testing to help patient management and avoid diagnostic errors.     

Dabigatran deliberate overdose: two cases and suggestions for laboratory monitoring

Context: Dabigatran etexilate (dabigatran) is a direct thrombin inhibitor anticoagulant agent. There is limited information about the changes in coagulation profile and outcomes in overdose. A monoclonal antibody has been developed to neutralize the anticoagulant effect of dabigatran. Case reports describe enhanced clearance of dabigatran by haemodialysis as an intervention to prevent haemorrhagic complications – however, the threshold for initiating haemodialysis is not well defined in an asymptomatic patient with normal renal function. Case details: Two patients presented following deliberate dabigatran overdoses. A 55-year-old woman ingested 10?×?150?mg dabigatran. A 21-year-old woman with a history of systemic lupus erythematosus and pulmonary embolus ingested 100?×?110?mg dabigatran. Both were admitted to the intensive care unit and managed expectantly. Serial coagulation tests normalized over 60 h. The half-life of dabigatran was not prolonged following overdose, being calculated between 7 and 11 h in each case. There was positive correlation between international normalized ratio (INR), prothrombin time (PT) and activated partial thromboplastin time (aPTT) with plasma dabigatran levels. Conclusion: There is limited experience with dabigatran overdoses. Normal aPTT, PT and INR assays 12 h following deliberate ingestion indicate that the drug concentration is not high. Individual risk assessment of bleeding risk needs to be formulated for each patient and expectant management is reasonable in the presence of normal renal function and absent risk factors for bleeding.     

Drugs affecting coagulation

For more than half a century, heparin and vitamin K antagonists have defined anticoagulant therapy in both the short-term and long-term management of thrombotic diseases. However, the limitations of these traditional anticoagulants have prompted the development of new drugs. In the past 15 years new agents with improved safety profile and greater ease of use that target almost every step of the coagulation cascade have been developed. These include factor Xa inhibitors and direct thrombin inhibitors. The mechanism of action of these new anticoagulants and also the ‘older’ agents are reviewed in this article.