Apixaban: an emerging oral factor Xa inhibitor

An Iron-Mesoionic Carbene Complex for Catalytic Intramolecular C-H Amination Utilizing Organic Azides

The synthesis of N-heterocycles is of paramount importance for the pharmaceutical industry. They are often synthesized through atom economic and environmentally unfriendly methods, generating significant waste. A less explored, but greener, alternative is the synthesis through the direct intramolecular C-H amination utilizing organic azides. Few examples exist by using this method, but many are limited due to the required use of stoichiometric amounts of Boc₂O. Herein, we report a homoleptic C,O-chelating mesoionic carbene-iron complex, which is the first iron-based complex that does not require the addition of any protecting groups for this transformation and that is active also in strong donor solvents such as THF or even DMSO. The achieved turnover number is an order of magnitude higher than any other reported catalytic system. A variety of C-H bonds were activated, including benzylic, primary, secondary, and tertiary. By following the reaction over time, we determined the presence of an initiation period. Kinetic studies showed a first-order dependence on substrate concentration and half-order dependence on catalyst concentration. Intermolecular competition reactions with deuterated substrate showed no KIE, while separate reactions with deuterium-labeled substrate resulted in a KIE of 2.0. Moreover, utilizing deuterated substrate significantly decreased the initiation period of the catalysis. Preliminary mechanistic studies suggest a unique mechanism involving a dimeric iron species as the catalyst resting state.

Comparative Incidence of Postoperative Hemorrhage in Vitreoretinal Surgery in Patients on Anti-Coagulants

BACKGROUND AND OBJECTIVE

Data regarding hemorrhagic complications of direct oral anticoagulants (DOACs) and vitreoretinal surgery are limited.

PATIENTS AND METHODS

Multicenter analysis of longitudinal, aggregated electronic health records of patients undergoing pars plana vitrectomy (PPV) with no prior history of ocular hemorrhage. Retrospective analysis of patients undergoing PPV between January 1, 2013, and December 31, 2019. The main outcomes were development of postoperative hemorrhagic complications within 1 month following vitreoretinal surgery.

RESULTS

A total of 58,131 eyes underwent PPV, with 2,956 (5.1%) on anticoagulant medication prior to surgery. Eight hundred twenty-eight eyes (1.4%) developed a postoperative hemorrhage. Of eyes with anticoagulation use, 50 of 2,956 (1.29%) developed a hemorrhage, whereas 778 of 55,175 (1.41%) of the eyes with no prior anticoagulation use developed a postoperative hemorrhage (P = .2107).

CONCLUSION

Use of DOACs prior to vitreoretinal surgery does not appear to be associated with increased rates of postoperative intraocular hemorrhage. [Ophthalmic Surg Lasers Imaging Retina. 2021;52:374-379.].

Hematoma Expansion Following Intracerebral Hemorrhage: Mechanisms Targeting the Coagulation Cascade and Platelet Activation

Hematoma expansion (HE), defined as a greater than 33% increase in intracerebral hemorrhage (ICH) volume within the first 24 hours, results in significant neurological deficits, and enhancement of ICH-induced primary and secondary brain injury. An escalation in the use of oral anticoagulants has led to a surge in the incidences of oral anticoagulation-associated ICH (OAT-ICH), which has been associated with a greater risk for HE and worse functional outcomes following ICH. The oral anticoagulants in use include vitamin K antagonists, and direct thrombin and factor Xa inhibitors. Fibrinolytic agents are also frequently administered. These all act via differing mechanisms and thus have varying degrees of impact on HE and ICH outcome. Additionally, antiplatelet medications have also been increasingly prescribed, and result in increased bleeding risks and worse outcomes after ICH. Aspirin, thienopyridines, and GPIIb/IIIa receptor blockers are some of the most common agents in use clinically, and also have different effects on ICH and hemorrhage growth, based on their mechanisms of action. Recent studies have found that reduced platelet activity may be more effective in predicting ICH risk, hemorrhage expansion, and outcomes, than antiplatelet agents, and activating platelets may thus be a novel target for ICH therapy. This review explores how dysfunctions or alterations in the coagulation and platelet cascades can lead to, and/or exacerbate, hematoma expansion following intracerebral hemorrhage, and describe the mechanisms behind these effects and the drugs that induce them. We also discuss potential future therapy aimed at increasing platelet activity after ICH.

Anticoagulation in Atrial Fibrillation

Patients with atrial fibrillation (AF) are at increased thromboembolic risk, and they suffer more severe strokes with worse outcomes. Most thromboembolic complications of AF are eminently preventable with oral anticoagulation, and the increasing numbers of AF patients mean antithrombotic therapy is the most crucial management aspect of this common arrhythmia. Despite the proven efficacy of warfarin, a string of limitations have meant that it is underused by physicians and patients alike. This has prompted a search for new anticoagulants that could overcome many of the inconveniences of dose variability and anticoagulant monitoring associated with warfarin, but without sacrificing efficacy in thromboprophylaxis. The arrival of new oral anticoagulants has been complemented by improved risk stratification schemes, which permit clinicians to easily and reliably identify patients requiring anticoagulation and their bleeding risk. These advances in AF treatment will hopefully translate into improved outcomes for patients, especially as our experience with the new agents grows.

Apixaban and oral implications

Background

Thrombotic disorders remain a leading cause of death in the Western world, and in this regard a number of anticoagulation treatment have been used, including heparins, fondaparinux, vitamin K antagonists (warfarin, acenocoumarol), and new oral anticoagulants such as apixaban. For years there has been great controversy regarding the use of anticoagulants in planning dental treatments that imply bleeding. The main concerns about using new oral anticoagulants in invasive dental procedures are bleeding due to the lack of an antidote, and the thrombotic risk of the disease for which anticoagulation was indicated in the first place.

Material and Methods

A literature search was conducted through May 2014 using the keyword “apixaban” for publications in the ISI Web of Knowledge. The search was extended to other databases (PubMed, Scopus and the Cochrane Library).

Results

Based on the results of the different studies, apixaban seems to be a good alternative to conventional anticoagulation and a reasonable treatment option, though its main and most common adverse effect is bleeding. Dose adjustment is needed in some patients, though regular laboratory monitoring is not required. The use of the drug in different patient populations will define its final indications and doses.

Conclusions

Regarding the use of apixaban in the dental setting, there is a compelling need for further clinical studies in order to establish more evidence-based guidelines for patients requiring antithrombotic treatment.

Key words:Apixaban, dental treatment, dental implications.

Determination of potential main sites of apixaban binding in human serum albumin by combined spectroscopic and docking investigations

Probing apixaban binding to human serum albumin: combining spectroscopic methods and docking investigations.

Apixaban

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

Triple Antiplatelet Therapy and Combinations with Oral Anticoagulants After Stent Implantation

Triple oral anticoagulation or triple antiplatelet therapies may be administered for various reasons. They reduce cardiac complications following percutaneous coronary intervention and stroke or other thromboembolic phenomenon in conditions such as atrial fibrillation. There is an elevated risk of severe bleeding, so it is necessary to balance risk and benefits. Newer oral anticoagulants and antiplatelet drugs may be considered; the number of options is increasing. This article examines triple therapies and the efficacy and safety of combinations of traditional anticoagulant and antiplatelet drugs, and reviews clinical trial data on novel agents. Guidelines to inform clinical decision-making are presented.

The need for novel anticoagulation therapy in acute coronary syndrome

As acute coronary syndrome (ACS) becomes more common nationwide and current anticoagulation regimens used in patients with ACS continue to possess their shortcomings, the need for new anticoagulants is on the rise. Although heparin and warfarin are used effectively in patients with ACS, they both have significant side effects and delivery issues. New factor Xa inhibitors offer an oral alternative that functions early in the coagulation cascade. The role of these new drugs in ACS is explored here. Electronic search strategies were used to collect reviews, randomized controlled trials, and other studies. Databases used included Medline and Cochrane Library and hand selection. Sources selected were limited to those that discussed factor Xa inhibitors in the context of ACS. Selected studies were then assessed for quality and relevance and those deemed relevant included for analysis. Some of the factor Xa inhibitors such as rivaroxaban offer anticoagulation as effective as, if not more effective, heparin and warfarin with lower risks of bleeding and other adverse effects such as heparin-induced thrombocytopenia. Many of these new agents also come in oral form, making them easy for patients to manage and use daily.

Stroke prevention in atrial fibrillation: concepts and controversies

Atrial fibrillation (AF) is the commonest cardiac rhythm disorder worldwide, affecting 1% of the general population. It is estimated that up to 16 million people in the US will suffer from the arrhythmia by 2050. AF is an independent stroke risk factor and associated with more severe strokes. For six decades, warfarin has been the only truly effective therapy to protect against stroke for patients with atrial fibrillation. Despite the proven worth of warfarin, its limitations have seen reluctance amongst physicians and patients to utilise this efficacious agent. This has meant that substantial numbers of patients are either unprotected against stroke or suboptimally protected with antiplatelet therapy.

Contemporary well-validated stroke risk factor schemes (CHA₂DS₂-VASc) now permit rapid but comprehensive evaluation of a patient’s risk for thromboembolism, allowing better identification of low-risk patients who do not require antithrombotic therapy, and whilst for those with ≥1 stroke risk factors require formal oral anticoagulation. Aspirin has been proven to be inferior to anticoagulation, and is not free of bleeding risk. We also have simple scores to easily evaluate a patient’s risk of haemorrhage (e.g. HAS-BLED).

The emergence of new oral anticoagulants should further improve stroke prevention in AF, and they successfully negotiate many of the hurdles to oral anticoagulation generated by warfarin’s limitations. Monitoring, reversal, and perioperative management are areas which require further investigation to enhance our ability to safely and effectively utilise the new agents.

Direct thrombin and factor Xa inhibition for stroke prevention in patients with atrial fibrillation

Nonvalvular atrial fibrillation (AF) is the most common clinically significant cardiac arrhythmia occurring in patients in the United States. The primary clinical consequence of AF is an increase in the risk and severity of strokes. Treatment guidelines recommend anticoagulation therapy for most patients with AF. One risk-stratification scheme, the CHADS2 index, is simple and widely used to determine the management of patients with AF in regard to stroke prevention. However, new schemes, such as CHA2DS2-VASc, further refine risk stratification to identify patients who would obtain a net clinical benefit from a particular management strategy, thus improving the quality of management. For patients with AF for whom oral anticoagulation (OAC) is advisable, vitamin K antagonist (VKA) therapy is well established and effective. However, OAC with VKAs presents challenges to prescribers and patients in maintaining therapeutic efficacy. Novel OACs may offer alternatives to VKAs. Dabigatran etexilate, a direct thrombin inhibitor, was approved by the US Food and Drug Administration (FDA) in 2010 for reducing the risk of stroke and systemic embolism in patients with nonvalvular AF. The activated factor X (factor Xa) inhibitor rivaroxaban was recently approved by the FDA both for prophylaxis of deep vein thrombosis, which may lead to pulmonary embolism in patients undergoing knee or hip arthroplasty, and for reducing the risk of stroke and systemic embolism in patients with nonvalvular AF. Apixaban, another factor Xa inhibitor, was recently shown to be effective for stroke prevention in patients with nonvalvular AF. This article reviews clinical considerations regarding new agents that may offer alternatives to VKA therapy for the prevention of stroke in patients with AF.

Therapeutic potential of apixaban in the prevention of venous thromboembolism in patients undergoing total knee replacement surgery

Anticoagulant prophylaxis for preventing venous thromboembolism (VTE) is a worldwide established procedure in hip and knee replacement surgery. Despite available anticoagulant prophylaxis, patients who undergo total knee arthroplasty (TKA) have a high incidence of venous VTE. In spite of their proven efficacy, the currently available anticoagulants have limitations that driven to develop new oral agents that directly target specific factors in the coagulation cascade, such as direct thrombin inhibitors and direct Factor Xa inhibitors, in an attempt to overcome some of the drawbacks with the traditional agents. Apixaban is a potent, selective direct inhibitor of the coagulation factor Xa, recently approved in Europe for the prevention of venous thromboembolism (VTE) in adult patients after total hip replacement (THR) or total knee replacement (TKR) surgery. Apixaban has been extensively studied worldwide in about 12,000 patients in four clinical studies that have demonstrated the efficacy and safety of apixaban respect to enoxaparin for the prevention of thromboembolism after major orthopedic surgery. Three of these trials involved 7,337 patients who undergo TKR: one phase II trial (APROPOS Study) and two large phase III trials (ADVANCE 1 and ADVANCE 2 Studies). ADVANCE 1 demonstrated that when compared with enoxaparin 30 mg twice daily for efficacy, apixaban did not meet the prespecified statistical criteria for noninferiority, but its use was associated with lower rates of clinically relevant bleeding. ADVANCE 2 showed that apixaban was superior to the European standard dose of enoxaparin of 40 mg once daily in term of efficacy, with a similar incidence of major bleeding. This review focuses the clinical efficacy and tolerability of oral apixaban for the prevention of VTE in adult patients following TKR surgery.

[Clinical management of the new anticoagulants]

The vitamin K antagonists (VKA) available for stroke prevention in patients with atrial fibrillation have many drawbacks due to their difficult clinical use and high risk of bleeding. Currently, several drugs are being developed as possible substitutes for VKA that have many advantages such as the lack of monitoring requirement and scarce pharmacologic and food interactions. The present article provides an update on the new oral anticoagulants that are in a more advanced stage of clinical research, their pharmacologic properties, advantages and disadvantages and their results in recent clinical trials.

Analysis of the projected utility of dabigatran, rivaroxaban, and apixaban and their future impact on existing Hematology and Cardiology Anticoagulation Clinics at The Johns Hopkins Hospital

The purpose of this study is to determine the percentage of patients in the Johns Hopkins Anticoagulation Clinics that are potential candidates for the new oral anticoagulants, dabigatran, rivaroxaban, and apixaban. A retrospective chart review was conducted of patients managed in the Johns Hopkins Cardiology and Hematology Anticoagulation Clinics between November 1, 2009 and October 31, 2010. Data elements collected include demographics, primary indication for anticoagulation, renal function, hepatic function, and concomitant medications. These factors were considered against product labeling guidelines and inclusion/exclusion criteria from clinical studies to derive candidacy status for each oral anticoagulant for each patient. Patients who met at least one caution or contraindication criteria were deemed "non-candidates"; potential dosage reductions of the new oral anticoagulants were not considered. Four hundred ninety-one patients participated in the study. Among participants, 63% would be dabigatran candidates, 62% rivaroxaban candidates, and 70% would be candidates for apixaban. Dabigatran use would be cautioned against in 34%, rivaroxaban in 18 %, and apixaban in 30%. Four percent had contraindications to dabigatran, whereas 21% had contraindications to rivaroxaban. More than 60% of patients in the Johns Hopkins Anticoagulation Clinics appear to be potential candidates for each of the new oral anticoagulants, assuming they are eventually approved for the same indications as warfarin. Many patients fell into the "cautioned" category, which demonstrates the complexity associated with selecting candidates for these new agents.

Stroke Prevention in Atrial Fibrillation: Where are We Now?

Atrial fibrillation is the commonest arrhythmia worldwide and is a growing problem. AF is responsible for 25% of all strokes, and these patients suffer greater mortality and disability. Warfarin has traditionally been the only successful therapy for stroke prevention, but its limitations have resulted in underutilisation. Major progress has been made in AF research, leading to improved management strategies. Better risk stratification permits identification of truly low-risk patients who do not require anticoagulation and we are able to simplify ourevaluation of a patient's bleeding risk.The advent of novel anticoagulants means warfarin is no longer the only choice for stroke prophylaxis. These drugs circumvent many of warfarin's inconveniences, but onlylong-term study and use will conclusively demonstrate how they compare to warfarin. The landscape of stroke prevention in AF has changed with effective alternatives to warfarin available for the first time in 60 years-but each new option brings new considerations.

New and emerging anticoagulant therapy for atrial fibrillation and acute coronary syndrome

Abstract Thrombosis is an underlying cause of many cardiovascular disorders, and generation of thrombi in the arterial circulation can lead to unstable angina, myocardial infarction, or ischemic stroke. Antithrombotic therapy is widely used, with proven benefit to prevent ischemic stroke and thromboembolic events in patients with atrial fibrillation (AF) or to prevent further ischemic complications in patients with acute coronary syndrome (ACS). Traditional anticoagulants (including unfractionated heparin, low-molecular-weight heparin, and warfarin) and antiplatelet agents (including aspirin, clopidogrel, and prasugrel) are typically used for these indications. Limitations to their use include variable pharmacokinetic and pharmacodynamic profiles, inability to inhibit fibrin-bound thrombin, risk of heparin-induced thrombocytopenia, delayed onset of action, numerous drug interactions, need for substantial laboratory monitoring and dosage titrations, hyporesponsiveness or resistance, hypersensitivity, adverse events, and bleeding. To overcome some of the limitations of traditional agents, new antithrombotic agents under development are highly selective for specific coagulation factors blocking the synthesis of thrombin. Clinicians must have an understanding of the new anticoagulants to aid in the selection of appropriate therapies for patients. We describe the most relevant phases II and III clinical trials that evaluated several recent emerging anticoagulant drugs for use in patients with AF or ACS. The advantages of many new agents include predictable pharmaco-dynamic response and pharmacokinetic parameters, allowing for fixed oral dosing with no need for laboratory monitoring. For patients with AF, dabigatran is already approved for the prevention of stroke and systemic embolism, rivaroxaban appears to be an effective alternative to warfarin in high-risk patients, and apixaban may also be an effective alternative to aspirin in patients unable to take warfarin. Otamixaban shows promise as an intravenous alternative for patients with ACS in the acute care setting. Likewise, rivaroxaban, dabigatran, and darexaban with or without dual antiplatelet therapy may be beneficial for secondary prevention of ischemic events in patients with ACS.

The practical management of intracerebral hemorrhage associated with oral anticoagulant therapy

Oral anticoagulant-associated intracerebral hemorrhage is increasing in incidence and is the most feared complication of therapy with vitamin K1 antagonists. Anticoagulant-associated intracerebral hemorrhage has a high risk of ongoing bleeding, death, or disability. The most important aspect of clinical management of anticoagulant-associated intracerebral hemorrhage is represented by urgent reversal of coagulopathy, decreasing as quickly as possible the international normalized ratio to values ≤1·4, preferably ≤1·2, together with life support and surgical therapy, when indicated. Protocols for anticoagulant-associated intracerebral hemorrhage emphasize the immediate discontinuation of anticoagulant medication and the immediate intravenous administration of vitamin K1 (mean dose: 10-20 mg), and the use of prothrombin complex concentrates (variable doses calculated estimate circulating functional prothrombin complex) or fresh-frozen plasma (15-30 ml/kg) or recombinant activated factor VII (15-120 μg/kg). Because of cost and availability, there is limited randomized evidence comparing different reversal strategies that support a specific treatment regimen. In this paper, we emphasize the growing importance of anticoagulant-associated intracerebral hemorrhage and describe options for acute coagulopathy reversal in this setting. Additionally, emphasis is placed on understanding current consensus-based guidelines for coagulopathy reversal and the challenges of determining best evidence for these treatments. On the basis of the available knowledge, inappropriate adherence to current consensus-based guidelines for coagulopathy reversal may expose the physician to medico-legal implications.

[A new deal with new anticoagulants?]

The anticoagulant market has been very active recently with the development of new compounds including injectable anti-Xa such as fondaparinux, already available, and idraparinux, already replaced by its new biotynilateed form, and new oral drugs which can be divided into anti-IIa with dabigatran already available, and anti-Xa, such as the recently marketed rivaroxaban and apixaban still in the development stage. Others are coming forward. The competition is strong and the place for each drug remains to be determined. This review discusses these new anticoagulants in terms of efficacy and tolerance based on data in the literature. These recent reports mainly concern prophylaxis for orthopedic surgery but also consider treatment of deep venous thrombosis. The results of studies in heart patients have raised much curiosity since they will be determinant in the future use of innovating compounds, which could replace current oral anticoagulants. This will be upcoming but not yet for tomorrow.