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.     

Dose escalating safety study of a new oral direct thrombin inhibitor, dabigatran etexilate, in patients undergoing total hip replacement: BISTRO I.

BACKGROUND: Dabigatran etexilate (BIBR 1048) is an oral direct thrombin inhibitor undergoing evaluation for the prevention of venous thromboembolism (VTE) following total hip replacement. Following oral administration, dabigatran etexilate is rapidly converted to its active form dabigatran (BIBR 953 ZW). OBJECTIVES: To determine the safe therapeutic range of dabigatran etexilate following total hip replacement. METHODS: In a multicenter, open-label, dose-escalating study, 314 patients received oral doses of dabigatran etexilate (12.5, 25, 50, 100, 150, 200 and 300 mg twice daily or 150 and 300 mg once daily) administered 4-8 h after surgery, for 6-10 days. Dose escalation was based on clinical and pharmacokinetic data. The primary safety outcome was major bleeding. The primary efficacy outcome included venographic deep vein thrombosis (DVT), symptomatic DVT and pulmonary embolism, during the treatment period. RESULTS: No major bleeding event was observed in any group, but two patients at the highest dose (300 mg twice daily) suffered bleeding from multiple sites associated with reduced renal clearance and prolonged pharmacodynamic (PD) parameters. A dose-response was demonstrated for minor bleeding events. Of the 289 treated patients, 225 patients had evaluable venograms. The overall incidence of DVT was 12.4% (28/225 patients). There was no consistent relationship between the dose and incidence of DVT, the highest incidence in any group being 20.8% (5/24 patients). The lowest dose (12.5 mg twice daily) showed a high rate of proximal DVT [12.5% (3/24)] and no increase in PD parameters. Peak and trough plasma concentrations, area under the dabigatran plasma concentration-time curve and PD parameters also increased in proportion with the dose. Higher dabigatran plasma concentrations were associated with lower DVT rates. Approximately 20% of the patients had low plasma concentrations after the first dose suggesting further optimization of the preliminary tablet formulation is required. CONCLUSIONS: Dabigatran etexilate demonstrates an acceptable safety profile, with a therapeutic window above 12.5 mg and below 300 mg twice daily. The low number of VTE events within each treatment group indicates a satisfactory antithrombotic potential, although the study was not powered for an efficacy analysis. Additional studies are ongoing to optimize oral absorption and the efficacy/safety balance.     

甲磺酸达比加群酯的合成

目的:研究和改进甲磺酸达比加群酯的合成工艺。方法:以4-甲氨基-3-硝基苯甲酸(2)和3-(吡啶-2-基氨基)丙酸乙酯(3)为原料,经酰氯化、酰胺化、中和成盐和还原制得重要中间体3-[[3-氨基-4-(甲氨基)苯甲酰基](吡啶-2-基)氨基]丙酸乙酯(5)。5再与N-(4-氰基苯基)甘氨酸经酰胺化、闭环、中和成盐、成脒、酰化,进而与甲磺酸成盐制得甲磺酸达比加群酯。结果:中间体及目标化合物经质谱、核磁共振谱、红外光谱等确证,整个工艺的总收率为33.9%。结论:本路线操作简便、成本较低、条件温和、步骤少,适合工业化生产。     

Safety of non-vitamin K antagonist oral anticoagulants - coronary risks

ABSTRACT

Introduction: Since the approval and commercialization of non-vitamin K antagonist oral anticoagulants (NOACs; apixaban, dabigatran, edoxaban, and rivaroxaban) several studies and meta-analyses have raised safety concerns regarding myocardial infarction (MI) risk among NOAC-treated patients, particularly with dabigatran. Uncertainty remains regarding the coronary risk associated with dabigatran, and whether this putative risk also applies to the other NOACs.

Areas covered: In this review, the coronary risks of NOACs based on findings from placebo-controlled trials are discussed, and randomized controlled trials and major cohort studies in AF patients are also appraised. We performed a random-effect meta-analysis, including both interventional trials and observational studies (“real-world” data). Further estimates were retrieved from the meta-analysis of coronary risk among NOAC-treated patients with concomitant AF and coronary disease.

Expert opinion: Currently, the best available data from both clinical trials and observational studies do not support the claim that patients treated with NOACs, including dabigatran, are at increased coronary risk. However, a definitive conclusion cannot be made (especially regarding dabigatran) and further data are required to address the coronary risks, mostly of high-risk patients. As with any therapeutic intervention, the possible complications should be balanced against the potential benefits at an individual patient level.