New direct oral anticoagulants--current therapeutic options and treatment recommendations for bleeding complications

A systematic review of patient-reported outcomes associated with the use of direct-acting oral anticoagulants

AIMS

Patient-reported outcomes (PROs) are a distinctive method of evaluating patient response to health care or treatment. This systematic review aimed to analyse the impact of PROs in patients on direct oral anticoagulant (DOAC) treatment, prescribed for any indication (e.g. venous thromboembolism treatment or atrial fibrillation) using controlled trials (CT) and real-world observational studies (OS).

METHODS

A systematic search of articles was conducted according to PRISMA guidelines using databases, with the last update in November 2018. The Cochrane Collaboration tool for assessing bias in randomized CTs and the Newcastle-Ottawa Scale adapted for cross-sectional studies were used. Outcomes evaluated were related to health-related quality of life (HRQoL), satisfaction, adherence and compliance.

RESULTS

Twenty-one original studies (6 CT, 15 OS) were included. HRQoL was assessed by 6 (1 CT, 5 OS) studies and reported that HRQoL scores were similar in patients on DOACs and warfarin. Patients prescribed DOACs presented higher HRQoL scores which were attributed to lack of intense monitoring required compared with warfarin but this was not statistically significant. The majority of studies (5 CT, 9 OS) investigated patient-reported satisfaction, indicating greater satisfaction with DOACs with significantly lower burden and increased benefit scores for patients on DOACs. Patient-reported expectations, compliance and adherence were similar for patients on DOACs and warfarin.

CONCLUSION

Patients appear to prefer treatment with DOACs vs warfarin. This is shown by the higher quality of life, satisfaction and adherence described in the studies. However, heterogeneity in the analysed studies does not allow firm conclusions.

Association of prothrombin complex concentrate administration and hematoma enlargement in non-vitamin K antagonist oral anticoagulant-related intracerebral hemorrhage

OBJECTIVE

To investigate parameters associated with hematoma enlargement in non-vitamin K antagonist oral anticoagulant (NOAC)-related intracerebral hemorrhage (ICH).

METHODS

This retrospective cohort study includes individual patient data for 190 patients with NOAC-associated ICH over a 5-year period (2011-2015) at 19 departments of neurology across Germany. Primary outcome was the association of prothrombin complex concentrate (PCC) administration with hematoma enlargement. Subanalyses were calculated for blood pressure management and its association with the primary outcome. Secondary outcomes include associations with in-hospital mortality and functional outcome at 3 months assessed using the modified Rankin Scale.

RESULTS

The study population for analysis of primary and secondary outcomes consisted of 146 NOAC-ICH patients with available follow-up imaging. Hematoma enlargement occurred in 49/146 (33.6%) patients with NOAC-related ICH. Parameters associated with hematoma enlargement were blood pressure ≥ 160mmHg within 4 hours and-in the case of factor Xa inhibitor ICH-anti-Xa levels on admission. PCC administration prior to follow-up imaging was not significantly associated with a reduced rate of hematoma enlargement either in overall NOAC-related ICH or in patients with factor Xa inhibitor intake (NOAC: risk ratio [RR] = 1.150, 95% confidence interval [CI] = 0.632-2.090; factor Xa inhibitor: RR = 1.057, 95% CI = 0.565-1.977), regardless of PCC dosage given or time interval until imaging or treatment. Systolic blood pressure levels < 160mmHg within 4 hours after admission were significantly associated with a reduction in the proportion of patients with hematoma enlargement (RR = 0.598, 95% CI = 0.365-0.978). PCC administration had no effect on mortality and functional outcome either at discharge or at 3 months.

INTERPRETATION

In contrast to blood pressure control, PCC administration was not associated with a reduced rate of hematoma enlargement in NOAC-related ICH. Our findings support the need of further investigations exploring new hemostatic reversal strategies for patients with factor Xa inhibitor-related ICH. Ann Neurol 2018;83:186-196.

Development of bioanalytical assays for variegin, a peptide-based bivalent direct thrombin inhibitor

AIM

Variegin is an anticoagulant peptide that will be tested in porcine models of percutaneous coronary intervention. We developed three bioanalytical assays for variegin quantitation and utilized these methods to evaluate pharmacokinetics of variegin in pigs. Results & methodology: The LC-MS/MS, thrombin amidolytic and modified thrombin time assays had a quantitation range of 21.6-5541.7, 10.8-5541.7 and 5.4-5541.7 nM in human plasma, respectively. The elimination half-lives obtained using the LC-MS/MS, modified thrombin time and thrombin amidolytic assays were 52.3 ± 4.4, 50.4 ± 5.9 and 67.7 ± 6.3 min, respectively.

CONCLUSION

We developed three bioanalytical assays for a novel direct thrombin inhibitor, variegin. The thrombin time assay is optimized for variegin quantitation during future porcine studies and clinical trials.

Management of bleeding in patients treated with direct oral anticoagulants

BACKGROUND

Recently, a new generation of direct-acting oral anticoagulants (DOACs) with a greater specificity towards activated coagulation factors was introduced based on encouraging results for efficacy and safety in clinical studies. An initial limitation of these new drugs was the absence of an adequate strategy to reverse the effect if a bleeding event occurs or an urgent invasive procedure has to be carried out.

MAIN TEXT

Specific reversing agents for DOACs have become available, however, and are now evaluated in clinical studies. For the anti-factor Xa agents (rivaroxaban, apixaban, and edoxaban) a number of studies have shown that the administration of prothrombin complex concentrate resulted in a correction of the prolonged prothrombin time and restored depressed thrombin generation after rivaroxaban treatment in a controlled trial in healthy human subjects. In view of the relatively wide availability of prothrombin complex concentrates, this would be an interesting option if the results can be confirmed in patients on oral factor Xa inhibitors who present with bleeding complications. More specific reversal can be achieved with andexanet, a new agent currently in development that competitively binds to the anti-factor Xa agents. For the direct thrombin inhibitor dabigatran, the administration of prothrombin complex concentrates showed variable results in various volunteer trials and efficacy at relatively high doses in animal studies. Recently, a Fab fragment of a monoclonal antibody (idarucizumab) was shown to be an effective reversal agent for dabigatran in human studies.

CONCLUSION

For the new generation of DOACs, several reversal strategies and specific antidotes are under evaluation, although most interventions need further evaluation in clinical trials.

Reversing the Effect of Oral Anticoagulant Drugs: Established and Newer Options

The vitamin K antagonists (VKAs) have been the standard (and only) oral anticoagulants used for the long-term treatment or prevention of venous thromboembolism or stroke in patients with atrial fibrillation. The coagulopathy induced by VKAs can be reversed with vitamin K, and in urgent situations, the vitamin K-dependent coagulation factors can be replaced by transfusion. In the last decade, a new class of oral anticoagulants has been developed, direct oral anticoagulants that bind to a specific coagulation factor and neutralize it. These compounds were shown to be effective and safe compared with the VKAs and were licensed for specific indications, but without a specific reversal agent. The absence of a reversal agent is a barrier to more widespread use of these agents. Currently, for the management of major life-threatening bleeding with the direct oral anticoagulants, most authorities recommend the use of four factor prothrombin complex concentrates. There are now three reversal agents in development and poised to enter the market. Idarucizumab is a specific antidote targeted to reverse the direct thrombin inhibitor, dabigatran, which was recently approved for use in the USA. Andexanet alfa is an antidote targeted to reverse the oral direct factor Xa inhibitors as well as the indirect inhibitor enoxaparin. Ciraparantag is an antidote targeted to reverse the direct thrombin and factor Xa inhibitors as well as the indirect inhibitor enoxaparin.

Novel Oral Anticoagulants for Venous Thromboembolism with Special Emphasis on Risk of Hemorrhagic Complications and Reversal Agents

Warfarin was the only oral anticoagulant available for the treatment of venous thromboembolism for about half a century until the recent approval of novel oral agents dabigatran, rivoraxaban and apixaban. This presents new classes of medications less cumbersome to use. They do not require frequent laboratory monitoring or have nurmerous drug interactions. On the other hand it also poses a challenge to the physicians deciding which agent to use in specific patient populations, how to predict the bleeding risk compared to warfarin and between the different novel agents and how to manage bleeding with relatively recent discovery of few potential antidotes. This review summarizes the major trials that led to the approval of these agents and their exclusion criteria helping physicians understand which patient types might not benefit from these agents. It provides clinical pearls invaluable in everyday practice such as transitioning between traditional and novel anticoagulants, dose adjustments for high risk populations, drug interactions and cost analysis. Futhermore, the review provides direct comparisons with warfarin and indirect comparisons among the novel agents in terms of efficacy and bleeding risk narrating the numbers of patients with intracranial, gastrointestinal and fatal hemorrhages in each of the major trials. We hope that this review will help the physicians inform their patients about the benefits and risks of these agents and enable them to make an informed selection of the most appropriate anticoagulant.

Allosteric Partial Inhibition of Monomeric Proteases. Sulfated Coumarins Induce Regulation, not just Inhibition, of Thrombin

Allosteric partial inhibition of soluble, monomeric proteases can offer major regulatory advantages, but remains a concept on paper to date; although it has been routinely documented for receptors and oligomeric proteins. Thrombin, a key protease of the coagulation cascade, displays significant conformational plasticity, which presents an attractive opportunity to discover small molecule probes that induce sub-maximal allosteric inhibition. We synthesized a focused library of some 36 sulfated coumarins to discover two agents that display sub-maximal efficacy (~50%), high potency (<500 nM) and high selectivity for thrombin (>150-fold). Michaelis-Menten, competitive inhibition, and site-directed mutagenesis studies identified exosite 2 as the site of binding for the most potent sulfated coumarin. Stern-Volmer quenching of active site-labeled fluorophore suggested that the allosteric regulators induce intermediate structural changes in the active site as compared to those that display ~80–100% efficacy. Antithrombin inactivation of thrombin was impaired in the presence of the sulfated coumarins suggesting that allosteric partial inhibition arises from catalytic dysfunction of the active site. Overall, sulfated coumarins represent first-in-class, sub-maximal inhibitors of thrombin. The probes establish the concept of allosteric partial inhibition of soluble, monomeric proteins. This concept may lead to a new class of anticoagulants that are completely devoid of bleeding.

Allosterism-based simultaneous, dual anticoagulant and antiplatelet action: allosteric inhibitor targeting the glycoprotein Ibα-binding and heparin-binding site of thrombin

BACKGROUND

Allosteric inhibition is a promising approach for developing a new group of anticoagulants with potentially reduced bleeding consequences. Recently, we designed sulfated β-O4 lignin (SbO4L) as an allosteric inhibitor that targets exosite 2 of thrombin to reduce fibrinogen cleavage through allostery and compete with glycoprotein Ibα to reduce platelet activation.

OBJECTIVE

To assess: (i) the antithrombotic potential of a novel approach of simultaneous exosite 2-dependent allosteric inhibition of thrombin and competitive inhibition of platelet activation; and (ii) the promise of SbO4L as the first-in-class antithrombotic agent.

METHODS

A combination of whole blood thromboelastography, hemostasis analysis, mouse arterial thrombosis models and mouse tail bleeding studies were used to assess antithrombotic potential.

RESULTS AND CONCLUSIONS

SbO4L extended the clot initiation time, and reduced maximal clot strength, platelet contractile force, and the clot elastic modulus, suggesting dual anticoagulant and antiplatelet effects. These effects were comparable to those observed with enoxaparin. A dose of 1 mg of SbO4L per mouse prevented occlusion in 100% of arteries, and lower doses resulted in a proportionally reduced response. Likewise, the time to occlusion increased by ~ 70% with a 0.5-mg dose in the mouse Rose Bengal thrombosis model. Finally, tail bleeding studies demonstrated that SbO4L does not increase bleeding propensity. In comparison, a 0.3-mg dose of enoxaparin increased the bleeding time and blood volume loss. Overall, this study highlights the promise of the allosteric inhibition approach, and presents SbO4L as a novel anticoagulant with potentially reduced bleeding side effects.

The Real-World Treatment of Hemorrhages Associated With Dabigatran and Rivaroxaban: A Multicenter Evaluation

PURPOSE

Adoption of the target-specific oral anticoagulants (TSOACs) has been slow; accordingly, lack of guidance for emergent reversal confounded by the need for "direct" reversal agents has contributed significantly to warfarin entrenchment in the medical community. The purpose of this analysis is to provide real-world experiences regarding the management of the hemorrhaging patient secondary to dabigatran and rivaroxaban.

METHODS

Retrospective review of patients admitted with a hemorrhage secondary to dabigatran or rivaroxaban were evaluated. Descriptive statistics were utilized for analysis.

RESULTS

Four hundred forty-four patients were screened for inclusion into the study; notably, 419 (94%) of the patients were excluded because the bleed was secondary to warfarin therapy. Of those included in this analysis (n = 25), gastrointestinal bleeding accounted for 21 events (84%), followed by intracranial (n = 2; 8%) and epistaxis (n = 2; 8%). Two patients (8%) expired during admission and 6 patients (24%) expired within 6 months after discharge from the hospital. Three (12%) minor bleeds, 7 (28%) major bleeds, and 15 (60%) life-threatening bleeds were identified. Minor bleeds required careful monitoring, supportive care, and cessation of anticoagulation therapy, whereas increasing severity required multiple interventions with prothrombin complex concentrate, recombinant activated factor 7, fresh frozen plasma, packed red blood cells, cryoprecipitate, and platelets.

CONCLUSION

The approach to the management of bleeding events borne from TSOACs has proven to be very heterogeneous. In the midst of this observation period, these facilities developed protocols, which created a stratification of bleeds and a more regimented approach to managing them. Although bleeding is less with new agents, the creation of pathways/algorithms for the management of TSOACs and education regarding clinical decision-making may be beneficial for the expeditious and appropriate management when these events arise.

Management of new oral anticoagulants related life threatening or major bleedings in real life: a brief report

Although new oral anticoagulants (NOAs) have been marketed in many countries, concern exists about the management of bleedings related to these drugs due to the lack of specific antidotes. The aim of our study was to report on real life management of NOAs-related life-threatening or major bleedings. We report data from consecutive cases of NOAs related major bleedings admitted to 4 hospitals since NOAs became marketed in Italy. We treated 8 patients, 4 males, with mean age 84 ± 7 years, 7 of whom were on dabigatran and one on rivaroxaban. The indication for NOA was atrial fibrillation. All bleedings were spontaneous and involving the gastro-intestinal tract. At the time of bleeding all patients had a drop in hemoglobin levels over 20 g/L. Creatinine clearance was ≤30 mL/min in 4 patients. All patients received general supportive measures, 4 of 8 patients were transfused with packed red cells and one patient received platelet transfusion. Three patients were treated with tranexamic acid and one patient on dabigatran received 4-factor prothrombin complex concentrate (PCC) with bleeding cessation, although coagulation parameters were not corrected. The median time for normalization of coagulation parameters was 3 days (range 1-6 days). All patients were discharged alive and NOAs were discontinued. In NOAs related major gastro-intestinal bleeding general supportive measures seem to be effective for the majority of patients. Despite promoting bleeding cessation, 4-factor PCC does not reverse abnormal coagulation parameters.

Current and developing strategies for monitoring and reversing direct oral anticoagulants in patients with non-valvular atrial fibrillation

OBJECTIVE

In light of the increasing clinical utilization of the direct oral anticoagulants (DOACs) among patients with non-valvular atrial fibrillation, this review evaluates strategies for monitoring and reversing the anticoagulant effect of these agents.

METHODS

We summarize the data currently available for laboratory monitoring and reversal of DOACs. Relevant literature was identified using search terms pertaining to oral anticoagulants, reversal agents, and laboratory monitoring using Pubmed, clinicaltrials.gov, and abstracts from recent major cardiovascular meetings.

RESULTS

Significant user appeal for the DOACs stems from the reliable pharmacokinetics of these agents, which render routine laboratory monitoring unnecessary for general use, as well as lower rates of bleeding as compared to warfarin. However, readily available laboratory tests have not been clinically validated for use with these agents. The ability to measure the anticoagulant effect of a DOAC in selected situations (e.g. serious bleeding, overanticoagulation, emergent procedures, and compliance monitoring) remains an unmet clinical need. Further, there is a paucity of data to guide treatment in patients receiving DOACs who experience a serious hemorrhage.

CONCLUSION

While evidence-based recommendations cannot be definitively provided for management of DOAC-related bleeding events at present, several targeted reversal agents are currently in development, and hold promise for solving this important clinical problem.

Long-term outcome of liver transplant patients with Budd-Chiari syndrome secondary to myeloproliferative neoplasms

BACKGROUND

A considerable proportion of patients receiving liver transplants for Budd-Chiari syndrome (BCS) suffer from myeloproliferative neoplasms (MPN). This study evaluated the long-term prognosis of liver-transplanted patients with BCS secondary to MPN and the effect of immunosuppression on MPN progression.

METHODS

A total of 78 patients with BCS were evaluated between 1982 and 2013. Of those, 40 patients suffered from polycythaemia vera (PV) and essential thrombocythaemia (ET). One patient had primary myelofibrosis (PMF). All patients received the standard immunosuppressive regimen. We retrospectively evaluated the long-term survival, clinical course and laboratory parameters of patients with MPN.

RESULTS

Exactly 29/41 patients (71%) with MPN survived ≥ 3 years [mean age 36 ± 11 years; females n = 27 (93%)]. Mean follow-up after orthotopic liver transplantation (OLT) was 12.4 ± 7.3 years (range 3-28 years). Five- and 10-year survival rates were not significantly different in patients with and without MPN (P = 0.81 and P = 0.66 respectively) or in patients with PV and ET (P = 0.29 and P = 0.55 respectively). Thrombosis and bleeding developed in 7/29 (24%) long-term MPN survivors with no significant difference between ET and PV (P = 0.18). In the long-term follow-up, there was no evidence of progression to overt myelofibrosis or acute myeloid leukaemia (AML). In the uni- and multivariate Cox-regression analyses, MPN did not influence survival after OLT.

CONCLUSIONS

Budd-Chiari syndrome patients with and without underlying MPN had similar long-term survival rates after OLT. There was no evidence of enhanced progression of MPN after OLT secondary to immunosuppressive therapy. However, major haemorrhage and recurrent thrombosis contributed to morbidity and mortality after OLT in those patients.

Trends in the development of oral anticoagulants

Anticoagulation remains the therapy of choice for the prevention and treatment of venous and arterial thromboembolic disorders which can cause major organ damage or death. Heparins represent the antithrombotic drugs of choice in short and medium-term prophylaxis and therapy of thromboembolic diseases. Fondaparinux, a synthetic and structural analog of the antithrombin-binding pentasaccharide domain of heparin, has selective anti-Xa activity and longer half-life. However, anticoagulants are poorly absorbed by oral route because of their high molecular weight, hydrophilicity and negative charges. Long-term anticoagulation therapy is problematic because of side effects and frequent monitoring. Formulation approaches are particularly promising.

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

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

Effective Reversal of Edoxaban-associated Bleeding with Four-factor Prothrombin Complex Concentrate in a Rabbit Model of Acute Hemorrhage

Background:

Edoxaban is an oral, selective direct factor Xa inhibitor approved in Japan for venous thromboembolism prevention after orthopedic surgery. Data are lacking regarding reversal strategies for edoxaban; this study assessed whether four-factor prothrombin complex concentrate (Beriplex®/Kcentra®; CSL Behring GmbH, Marburg, Germany) can effectively reverse its effects on hemostasis using a previously described rabbit model.

Methods:

The study comprised assessments of thrombin generation in vitro, pharmacokinetic parameters, and edoxaban reversal in vivo. In a blinded in vivo stage, a standardized kidney incision was performed in animals (n = 11 per group) randomized to receive vehicle + saline, edoxaban (1,200 μg/kg) + saline, or edoxaban (1,200 μg/kg) + four-factor prothrombin complex concentrate (50 IU/kg). Animals were monitored for treatment impact on hemostasis and coagulation parameters. Data are median (range). Statistical tests were adjusted for multiple testing.

Results:

Edoxaban administration increased blood loss (30 [2 to 44] ml) and time to hemostasis (23 [8.5 to 30.0] min) compared with the control group (3 [1 to 8] ml and 3 [2.0 to 5.0] min, respectively). Biomarkers of coagulation (prothrombin time, activated partial thromboplastin time, whole blood clotting time) and thrombin generation parameters (e.g., peak thrombin, endogenous thrombin potential, lag time) were also affected by edoxaban. Administration of four-factor prothrombin complex concentrate significantly reduced time to hemostasis (to 8 [6.5 to 14.0] min, observed P &lt; 0.0001) and total blood loss (to 9 [4 to 22] ml, observed P = 0.0050) compared with the edoxaban + saline group. Of the biomarkers tested, prothrombin time, whole blood clotting time, and endogenous thrombin potential correlated best with clinical parameters.

Conclusion:

In a rabbit model of hemostasis, four-factor prothrombin complex concentrate administration significantly decreased edoxaban-associated hemorrhage.

The potential of target-specific oral anticoagulants for the acute and long-term treatment of venous thromboembolism

BACKGROUND

Venous thromboembolism (VTE) comprises both deep vein thrombosis and pulmonary embolism. VTE is a leading cause of morbidity and mortality worldwide and its increasing incidence and prevalence are a major health concern. The primary medical objective during the acute phase of VTE treatment is to prevent thrombus extension and embolization. Extended treatment aims to prevent or minimize long-term complications, such as recurrent VTE, post-thrombotic syndrome and chronic thromboembolic pulmonary hypertension.

SCOPE

Anticoagulant therapy has been the mainstay of treatment for VTE and traditionally involves initial therapy with heparin, overlapping with and followed by a vitamin K antagonist. Although effective, standard heparin/vitamin K antagonist therapy has several limitations that can be overcome by more recently developed target-specific oral anticoagulants (TSOACs). These agents have predictable pharmacokinetics, a rapid onset of action and few drug-drug or drug-food interactions. Furthermore, TSOACs offer convenient anticoagulation without the need for routine coagulation monitoring and dose adjustment.

FINDINGS

The efficacy and safety data from phase III clinical trials support the use of TSOACs for VTE treatment, including in special patient populations. Risk-stratification tools and strategies have been developed to assist physicians in managing anticoagulation treatment.

CONCLUSIONS

Rivaroxaban is the first TSOAC to gain widespread approval for the treatment of acute deep vein thrombosis and pulmonary embolism and the long-term prevention of recurrent VTE as monotherapy. Dabigatran has also been approved for this indication recently. TSOACs, especially as monotherapy, represent a paradigm shift in clinical practice for the management of patients with VTE.

Non-vitamin K oral anticoagulants in atrial fibrillation: Where are we now?

Atrial fibrillation (AF) confers increased risk of stroke and other thromboembolic events, and oral anticoagulation therefore is the essential part of AF management to reduce the risk of these complications. Until recently, the vitamin K antagonists (VKAs, e.g., warfarin) were the only oral anticoagulants available, acting by decreased synthesis of vitamin K-dependent coagulation factors (II, VI, IX, and X). The VKAs had many limitations: delayed onset and prolonged offset of action, variability of anticoagulant effect among patients, multiple food and drug interactions affecting pharmacological properties of warfarin, narrow therapeutic window, and obligatory regular laboratory control, which all made warfarin "inconvenient" both for patients and clinicians. The limitations of VKAs led to development of a new class of drugs collectively defined as non-VKA oral anticoagulants (NOACs), which included direct thrombin inhibitors (dabigatran) and factor Xa inhibitors (rivaroxaban, apixaban, and edoxaban). The NOACs avoid many of the VKA drawbacks. In this review, we will focus on the current evidence justifying the use of NOACs in non-valvular AF.

Warfarin versus dabigatran etexilate: an assessment of efficacy and safety in patients with atrial fibrillation

INTRODUCTION

Oral anticoagulation is the mainstay for stroke and thromboembolic event prevention in patients with atrial fibrillation (AF). Given limitations of warfarin therapy, non-vitamin K oral anticoagulants have been developed including direct thrombin inhibitors (i.e., dabigatran etexilate). Dabigatran etexilate has been tested thoroughly in terms of efficacy and safety in clinical trials and studies, involving 'real-world' cohorts. In this review, currently available evidence in patients with non-valvular AF is discussed.

AREAS COVERED

The pharmacology, efficacy and safety, and current aspects of use of dabigatran etexilate in patients with non-valvular AF are reviewed in a comparative manner to warfarin both for chronic anticoagulation and in different clinical settings.

EXPERT OPINION

Dabigatran etexilate appeared to have several pharmacokinetic and pharmacodynamic advantages over warfarin, as well as a favorable efficacy and safety profile being at least noninferior and often superior to warfarin in patients with non-valvular AF. The latter was shown in the clinical trials, meta-analyses and studies with 'real-world' data. Currently ongoing trials will expand the body of evidence on warfarin and will aid decision making in currently controversial areas. Important limitations of dabigatran etexilate include contraindications for its use in patients with prosthetic heart valves and end-stage chronic kidney disease.

New oral anticoagulant-induced bleeding: clinical presentation and management

Bleeding is a significant complication of anticoagulant therapy. With the emergence of new oral anticoagulants (NOACs; ie, direct factor IIa or Xa inhibitors), this risk is further compounded by the lack of validated reversal strategies for these agents. Emerging postmarketing evidence suggests that the bleeding risks are in line with results observed in head-to-head clinical trials of NOACs versus traditional anticoagulants. Several guidelines have recommended the use of hemostatic agents for NOAC reversal in patients with life-threatening bleeding. Ultimately, adequately powered studies will be crucial for full assessment of the effectiveness and safety of any proposed reversal strategies.

New oral anticoagulants: clinical indications, monitoring and treatment of acute bleeding complications

New oral anticoagulants like the direct thrombin inhibitor, dabigatran (Pradaxa®), and factor Xa-inhibitors, rivaroxaban (Xarelto®) and apixaban (Eliquis®) are available for prophylaxis and treatment of thromboembolic disease. They are emerging alternatives to warfarin and provide equal or better clinical outcome together with reduced need for routine monitoring. Methods for measuring drug concentrations are available, although a correlation between plasma drug concentrations and the risk of bleeding has not been firmly established. Standard laboratory measures like prothrombin time and activated partial thromboplastin time are not sensitive enough to detect thrombin or factor Xa inhibition provided by new oral anticoagulants. Thus, these standard tests may only be used as a crude estimation of the actual anticoagulation status. Further challenges regarding patients receiving new oral anticoagulants who presents with major bleeding or need for emergency surgery pose a unique problem. No established agents are clinically available to reverse the anticoagulant effect, although preclinical data report prothrombin complex concentrate as more efficient than fresh frozen plasma or other prohaemostatic agents. This review summaries current knowledge on approved new oral anticoagulants and discusses clinical aspects of monitoring, with particular focus on the management of the bleeding patient.

New oral anticoagulants and oculoplastic surgery

The use of oral anticoagulants is increasing because of the rising prevalence of atrial fibrillation and other cardiovascular diseases that occur in an aging population. In the last decade, several new oral anticoagulants have emerged, comprising the direct thrombin inhibitor dabigatran and the factor Xa inhibitors apixaban and rivaroxaban. Although these new anticoagulants may not affect clear corneal cataract surgery, their use will impact the management of patients having eyelid, orbital, and nasolacrimal procedures. The objective of this review is to provide a concise and practical approach to the perioperative management of patients who require an oculoplastic procedure and are receiving these new anticoagulants.

Conventional and new oral anticoagulants in the treatment of chest disease and its complications

Oral anticoagulants block the coagulation cascade either by an indirect mechanism (e.g., vitamin K antagonists) or by a direct one (e.g., the novel oral anticoagulants). Vitamin K antagonists are widely used as treatment of venous thromboembolism and for stroke prevention in patients with atrial fibrillation. Although low molecular weight heparin remains the first line in venous thromboembolism prophylaxis, more recently the novel oral anticoagulants such as dabigatran (initial dose of 110 mg within 1-4 h after surgery, followed by the full dose of 220 mg once daily), rivaroxaban (dose of 10 mg once daily, with the first dose administered 6-10 h after the surgery), and apixaban (dose of 2.5 mg twice daily, starting 12-24 h after surgery, but available only in Europe) are approved for prophylaxis in patients undergoing major orthopedic surgery. The period in which thromboembolic risk abates remains uncertain, and trials of extended therapy are still ongoing. After showing at least noninferiority to warfarin in RE-LY, ROCKET-AF, and ARISTOTLE trials, dabigatran (110 or 150 mg twice daily), rivaroxaban (20 or 15 mg once daily), and apixaban (5 mg twice daily), respectively, were approved also for stroke prevention in patients with atrial fibrillation. While awaiting long-term safety data, the choice among all these available therapies should be based on patient preferences, compliance, and ease of administration, as well as on local factors affecting cost-effectiveness.

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.

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.

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.

[Critical haematuria after prostate biopsies with RIVAROXABAN. Case report]

Managing patients with new oral anticoagulants in perioperative period is not yet well protocolized. We report a clinical case of a critical haematuria after prostate biopsies to a patient treated with RIVAROXABAN. Monitoring and treatment of the haematuria have been difficult due to the lack of biological control and antidote for this treatment.

Antithrombotic therapy for stroke prevention in non-valvular atrial fibrillation

The world faces an epidemic of atrial fibrillation and atrial fibrillation-related stroke. An individual's risk of atrial fibrillation-related stroke can be estimated with the CHADS(2) or CHA(2)DS(2)VASc scores, and reduced by two-thirds with effective anticoagulation. Vitamin K antagonists, such as warfarin, are underused and often poorly managed. The direct thrombin inhibitor dabigatran etexilate and factor Xa inhibitors rivaroxaban and apixaban are new oral anticoagulants that are at least as efficacious and safe as warfarin. Their advantages are predictable anticoagulant effects, low propensity for drug interactions, and lower rates of intracranial haemorrhage than with warfarin. A disadvantage is the continuing need to develop and validate rapidly effective antidotes for major bleeding and standardised tests that accurately measure plasma concentrations and anticoagulant effects, together with the disadvantage of possible higher rates of gastrointestinal haemorrhage and greater expense than with warfarin. The new oral anticoagulants should increase the number of patients with atrial fibrillation at risk of stroke who are optimally anticoagulated, and reduce the burden of atrial fibrillation-related stroke.