Novel oral anticoagulants in cardiovascular disease

Simultaneous determination of Rivaroxaban and TAK-438 in rat plasma by LC-MS/MS: application to pharmacokinetic interaction study

Aim: A sensitive and reliable LC-MS/MS method has been established and validated to the quantitation of rivaroxaban (RIV) and TAK-438 in rat plasma using carbamazepine as internal standard. Results: The procedure of method validation was conducted according to the guidelines of EMA and US FDA. At the same time, the method was applied to pharmacokinetic interactions study between RIV and TAK-438 for the first time. When RIV and TAK-438 co-administration to rats, main pharmacokinetic parameters of TAK-438 like AUC_(0-t), AUC_(0-∞) and C_max had statistically significant increase. The main pharmacokinetic parameters of RIV have no statistically significant difference (p > 0.05) when co-administered except for t_1/2 (p < 0.01). Conclusion: The results indicated that drug-drug interactions occurred between RIV and TAK-438 when co-administered to rats.

Thrombocytopenia: A possible side effect of apixaban

Apixaban is becoming more frequently prescribed for stroke prevention in patients with atrial fibrillation, and even rare side effects such as thrombocytopenia should be considered and monitored closely.

Critical Issues and Recent Advances in Anticoagulant Therapy: A Review

As the population is aging, clinicians are coming across more patients with atrial fibrillation and venous thromboembolism requiring anticoagulation to prevent stroke and systemic embolisms. Due to a high prevalence and unfavorable consequences, managing thromboembolic diseases have become areas of clinical concern. Traditional anticoagulants like heparin, low molecular weight heparin and warfarin have been used for the prevention and treatment of venous and arterial thromboses. But, issues of bleeding, parenteral route of administration, or the need for frequent monitoring due to variability in response respectively limit their use. The article gives an overview of coagulation along with existing therapy available for anticoagulation and to present an update on utility and recent advances of new oral anticoagulants (NOACs) beginning from their nomenclature, advantages, disadvantages, precautions and contraindications compared with those of vitamin K antagonists (VKAs) based on a large number of recent studies and clinical trials.

Would the Use of Edoxaban Be Cost-effective for the Prevention of Stroke and Systemic Embolism in Patients With Nonvalvular Atrial Fibrillation in Spain?

INTRODUCTION AND OBJECTIVES

To assess the cost-effectiveness of edoxaban vs acenocoumarol in the prevention of stroke and systemic embolism in patients with nonvalvular atrial fibrillation (NVAF) in Spain.

METHODS

Markov model, adapted to the Spanish setting from the perspective of the National Health System, stimulating the progression of a hypothetical cohort of patients with NVAF throughout their lifetime, with different health states: stroke, haemorrhage, and other cardiovascular complications. Efficacy and safety data were obtained from the available clinical evidence (mainly from the phase III ENGAGE AF-TIMI 48 study). The costs of managing NVAF and its complications were obtained from Spanish sources.

RESULTS

Edoxaban use led to 0.34 additional quality-adjusted life years (QALY) compared with acenocoumarol. The incremental cost with edoxaban was 3916€, mainly because of higher pharmacological costs, which were partially offset by lower costs of treatment monitoring and managing NVAF events and complications. The cost per QALY was 11 518€, within the thresholds commonly considered cost-effective in Spain (25 000-30 000 €/QALY). The robustness of the results was confirmed by various sensitivity analyses.

CONCLUSIONS

Edoxaban is a cost-effective alternative to acenocoumarol in the prevention of stroke and systemic embolism in patients with NVAF in Spain.

Indication, Patient Selection, and Referral Pathways for Left Atrial Appendage Closure

Left atrial appendage closure (LAAC) has emerged as a viable option for stroke prevention, especially in those intolerant of or not suitable for long-term oral anticoagulation therapy. This article describes the clinical characteristics, indications, and a proposed referral system for potential LAAC patients. Patient selection remains a challenge because of the paradox between the available randomized data on this intervention and the actual patient population who may gain maximum benefit. Further investigations comparing different LAAC devices with each other and with novel oral anticoagulants are needed. Also, the optimal antithrombotic regimen post-procedure has yet to be determined.

Place of non-vitamin K antagonist oral anticoagulants in anticoagulant-antiplatelet combinations in peripheral artery disease

Non-vitamin K antagonist oral anticoagulants are becoming increasingly important in the prophylaxis and treatment of thrombosis in atrial fibrillation and venous thromboembolism. Antiplatelets are widely prescribed in the primary and secondary prevention of cardiac and vascular diseases. There are potentially numerous situations where anticoagulants and antiplatelets may be combined; these combinations have been explored in coronary artery disease, and some have been included in updated recommendations. Is it legitimate to transpose these recommendations to the management of peripheral artery disease? The specific characteristics of the treated vessels, the stents used, the respective frequencies of stent thrombosis and its effect on the target organ are probably different, and explain why opinions differ. However, because of a lack of evidence, empirical behaviours are being established without scientific validation. This review of the literature details the situations in which combinations of an anticoagulant and an antiplatelet have been explored in peripheral artery disease. We discuss the issue of antithrombotic combinations in stable peripheral artery disease and for vascular or endovascular surgery.

NOAC monitoring, reversal agents, and post-approval safety and effectiveness evaluation: A cardiac safety research consortium think tank

Four non-vitamin K antagonist oral anticoagulants (dabigatran, rivaroxaban, apixaban, and edoxaban) have been approved in the United States for treatment of atrial fibrillation (AF) and venous thromboembolic disease. They have been as or more effective than the prior standards of care, with less fatal or intracranial bleeding, fewer drug and dietary interactions, and greater patient convenience. Nonetheless, the absence of the ability for clinicians to assess compliance or washout with a simple laboratory test (or to adjust dosing with a similar assessment) and the absence of an antidote to rapidly stop major hemorrhage or to enhance safety in the setting of emergent or urgent surgery/procedures have been limitations to greater non-vitamin K antagonist oral anticoagulant usage and better thromboembolic prevention. Accordingly, a Cardiac Research Safety Consortium "think tank" meeting was held in February 2015 to address these concerns. This manuscript reports on the discussions held and the conclusions reached at that meeting.

Carbon-13 and carbon-14 labeled dabigatran etexilate and tritium labeled dabigatran

Dabigatran etexilate or pradaxa, a novel oral anticoagulant, is a reversible, competitive, direct thrombin inhibitor. It is used to prevent strokes in patients with atrial fibrillation and the formation of blood clots in the veins (deep venous thrombosis) in adults who have had an operation to replace a hip or a knee. Pradaxa is the only novel oral anticoagulant available with both proven superiority to warfarin and a specific reversal agent for use in rare emergency situations. The detailed description of the synthesis of carbon-13 and carbon-14 labeled dabigatran etexilate, and tritium labeled dabigatran is described. The synthesis of carbon-13 dabigatran etexilate was accomplished in eight steps and in 6% overall yield starting from aniline-¹³ C₆ . Ethyl bromoacetate-1-¹⁴ C was the reagent of choice in the synthesis of carbon-14 labeled dabigatran etexilate in six steps and 17% overall yield. Tritium labeled dabigatran was prepared using either direct tritium incorporation under Crabtree's catalytic conditions or tritium-dehalogenation of a diiodo-precursor of dabigatran.

Novel oral anticoagulants in non-valvular atrial fibrillation

Atrial fibrillation is the most frequent arrhythmia in clinical practice, reaching 2% of the people in the world and is associated with systemic embolism. Thus, the use of anticoagulants is indicated if CHA2DS2-VASc score ≥ 2 or in patients with previous transient ischemic attack or stroke. For decades, warfarin, a vitamin K antagonist, was the only choice for chronic oral anticoagulation. Recently, novel oral anticoagulants (NOACs) have been introduced, offering similar (or better) effectiveness, safety, and convenience to the vitamin K antagonists. Dabigatran was the first NOAC approved and is a direct thrombin inhibitor. Rivaroxaban and apixaban are factor Xa inhibitors. They display rapid onset of action, more predictable of pharmacological profile, less interactions with other drugs, lack of significant effects in the diet, and less risk of intracranial hemorrhage than warfarin. Despite that dose adjustment is necessary for patients with chronic kidney disease or according to body weight, these new drugs do not require regular monitoring. There are recommendations for the start and follow-up therapy with NOACs, planning for cardioversion, ablation and surgical interventions and the management of bleeding. This article is a review of the major studies of the NOACs. The clinical use of these drugs in patients with non-valvular atrial fibrillation is presented.

Educating orally anticoagulated patients in drug safety: a cluster-randomized study in general practice

BACKGROUND

Orally anticoagulated patients with insufficient knowledge about their treatment have a higher risk of complications. Standardized patient education could raise their level of knowledge and improve time spent within target INR range.

METHODS

This cluster randomized trial included 319 anticoagulated patients drawn from 22 general medical practices. 185 patients received patient education, conducted by practice nurses, consisting of a video, a brochure, and a questionnaire; 134 control patients received only the brochure. The primary endpoint was knowledge about treatment six months after the patient education session. The secondary endpoints were time in the INR (international normalized ratio) target range and complications of anticoagulation.

RESULTS

Patients in the intervention and control groups were of comparable mean age (73 vs. 72 years). They answered a comparable number of questions correctly before the intervention (6.8 ± 0.2 vs. 6.7 ± 0.2) but differed significantly on this measure at six months (9.9 ± 0.2 vs. 7.6 ± 0.2, mean difference 2.3 questions, 95% confidence interval [CI] 1.5-3.1, p< 0.001). In the six months prior to the intervention, the INR was in the target range 65 ± 2% vs. 66 ± 3% of the time; in the six months afterward, 71 ± 1% vs. 64 ± 3% of the time (mean difference 7 percentage points, 95% CI -2 to -16 percentage points, p = 0.11). The complication rates were comparable in the two groups (12% vs. 16%, p = 0.30). Patients in the intervention group approved of patient education sessions to a greater extent than control patients (87% vs. 56%).

CONCLUSION

Patient education was found to be practical, to improve knowledge relating to patient safety in a durable manner, and to meet with the approval of the patients who received it. There was a statistically non-significant trend toward an improvement of the time spent in the INR target range. In view of the major knowledge deficits of orally anticoagulated patients, standardized patient education ought to be made a part of their routine care.

New oral anticoagulants: their advantages and disadvantages compared with vitamin K antagonists in the prevention and treatment of patients with thromboembolic events

Despite the discovery and application of many parenteral (unfractionated and low-molecular-weight heparins) and oral anticoagulant vitamin K antagonist (VKA) drugs, the prevention and treatment of venous and arterial thrombotic phenomena remain major medical challenges. Furthermore, VKAs are the only oral anticoagulants used during the past 60 years. The main objective of this study is to present recent data on non-vitamin K antagonist oral anticoagulants (NOACs) and to analyze their advantages and disadvantages compared with those of VKAs based on a large number of recent studies. NOACs are novel direct-acting medications that are selective for one specific coagulation factor, either thrombin (IIa) or activated factor X (Xa). Several NOACs, such as dabigatran (a direct inhibitor of FIIa) and rivaroxaban, apixaban and edoxaban (direct inhibitors of factor Xa), have been used for at least 5 years but possibly 10 years. Unlike traditional VKAs, which prevent the coagulation process by suppressing the synthesis of vitamin K-dependent factors, NOACs directly inhibit key proteases (factors IIa and Xa). The important indications of these drugs are the prevention and treatment of deep vein thrombosis and pulmonary embolisms, and the prevention of atherothrombotic events in the heart and brain of patients with acute coronary syndrome and atrial fibrillation. They are not fixed, and dose-various strengths are available. Most studies have reported that more advantages than disadvantages for NOACs when compared with VKAs, with the most important advantages of NOACs including safety issues (ie, a lower incidence of major bleeding), convenience of use, minor drug and food interactions, a wide therapeutic window, and no need for laboratory monitoring. Nonetheless, there are some conditions for which VKAs remain the drug of choice. Based on the available data, we can conclude that NOACs have greater advantages and fewer disadvantages compared with VKAs. New studies are required to further assess the efficacy of NOACs.

Rationale and design of a study exploring the efficacy of once-daily oral rivaroxaban (X-TRA) on the outcome of left atrial/left atrial appendage thrombus in nonvalvular atrial fibrillation or atrial flutter and a retrospective observational registry providing baseline data (CLOT-AF)

There are still many unresolved issues concerning patient outcomes and prognostic factors in patients with atrial fibrillation (AF) and left atrial/left atrial appendage (LA/LAA) thrombi. Rivaroxaban (Xarelto®), a potent and highly selective oral, direct factor Xa inhibitor, is a new therapeutic option in this setting. The planned study program will consist of a prospective interventional study (X-TRA) and a retrospective observational registry (CLOT-AF). The primary objective of the X-TRA study is to explore the efficacy of rivaroxaban in the treatment of LA/LAA thrombi in patients with nonvalvular AF or atrial flutter, scheduled to undergo cardioversion or AF ablation, in whom an LA/LAA thrombus has been found on transesophageal echocardiography (TEE) before the procedure. The primary end point is the complete LA/LAA thrombus resolution rate at 6 weeks of end of treatment confirmed by TEE. The secondary objectives are to describe categories of thrombus outcome in patients (resolved, reduced, unchanged, larger, or new) confirmed on TEE at the end of treatment (after 6 weeks of treatment), incidence of the composite of stroke and noncentral nervous system systemic embolism at the end of treatment and during follow-up, and incidence of all bleeding at the end of treatment and during follow-up. The objective of the CLOT-AF registry is to provide retrospective thrombus-related patient outcome data after standard-of-care anticoagulant treatment in patients with nonvalvular AF or atrial flutter, who have TEE-documented LA/LAA thrombi. The data will be used as a reference for the prospective X-TRA study. In conclusion, X-TRA and CLOT-AF will provide some answers to the many unresolved issues concerning patient outcomes and prognostic factors in patients with AF and LAA thrombi. Results from this study program would provide the first prospective interventional study (X-TRA) and a large international retrospective observational registry (CLOT-AF) on the prevalence and natural history of LA/LAA thrombi. Unique data on clot resolution with rivaroxaban in a prospective cohort would be obtained in X-TRA.

Potential use of NOACs in developing countries: pros and cons

PURPOSE

Although vitamin K antagonists (VKAs) are effective for long-term thromboprophylaxis in atrial fibrillation (AF), their limitations have led to widespread underutilisation, especially in the developing world. Novel oral anticoagulants (NOACs) have emerged as promising alternatives to VKAs, although there are some particular considerations and challenges to their introduction in developing countries. This review summarises the current state of antithrombotic management of AF in the developing world, explores the early evidence for the NOACs and describes some of the special considerations that must be taken into account when considering the role of the NOACs within developing countries' health care systems.

METHODS

A literature search was conducted via PubMed and Google Scholar to find articles published in English between the years 2000 to 2014. Search terms used were "atrial fibrillation", "oral anticoagulants", "warfarin", "NOACs", "dabigatran", "rivaroxaban", "apixaban", "edoxaban", "time in therapeutic range", "International Normalized Ratio" "cost-effectiveness", "stroke", "adverse-drug reactions" and "drug-drug interactions", together with the individual names of developing countries as listed by the World Bank. We reviewed the results of randomized clinical trials, relevant retrospective and prospective studies, case-studies and review articles.

RESULTS

Many developing countries lack or have sporadic data on the quality of AF management, making it difficult to anticipate the potential impact of NOACs in these settings. The utilisation of anticoagulants for AF appears highly variable in developing countries. Given the issues associated with VKA therapy in many developing countries, NOACs offer some potential advantages; however, there is insufficient evidence to advocate the widespread replacement of warfarin at present. VKAs may continue to have a role in selected patients or countries, especially if alternative monitoring strategies can be utilised.

CONCLUSION

The evaluation of the introduction of NOACs should consider safety, budget concerns and the quality of oral anticoagulation care achieved by each country. Prospective registries will be important in developing countries to better elucidate the comparative safety, efficacy and cost-effectiveness of NOACs and VKAs as NOACs are introduced into practice.

Edoxaban

Vitamin K antagonists (VKAs) remain the standard therapy for anticoagulation in prevention and treatment of venous thromboembolism (VTE) and for the prevention of stroke in atrial fibrillation (AF). Due to numerous limitations of VKAs, target-specific oral anticoagulants have been developed. Edoxaban is a direct activated factor X inhibitor with attractive features among which are once daily dosing, no need for routine monitoring, and minimal drug–drug interactions. In patients undergoing orthopedic surgery, edoxaban was superior to enoxaparin in preventing VTE. Furthermore, a recent large-scale phase III trial in patients with symptomatic VTE demonstrated that edoxaban was noninferior to warfarin in preventing recurrent VTE and reduced bleeding. In the largest trial of anticoagulation in patients with AF to date, edoxaban was noninferior to warfarin in the prevention of stroke or systemic embolism and reduced bleeding and cardiovascular mortality. This review provides an overview of the pharmacology, clinical trial results, and potential indications for edoxaban.