Reversal of rivaroxaban and dabigatran by prothrombin complex concentrate: a randomized, placebo-controlled, crossover study in healthy subjects

Prothrombin complex concentrates reduce blood loss in murine coagulopathy induced by warfarin, but not in that induced by dabigatran etexilate

BACKGROUND

Both established oral anticoagulants such as warfarin and newer agents such as dabigatran etexilate (DE) effectively prevent thromboembolic disease, but may provoke bleeding. Limited clinical data exist linking oral anticoagulant reversal and bleeding tendency, as opposed to surrogate laboratory markers.

OBJECTIVE

 To quantify bleeding in warfarin-anticoagulated and DE-anticoagulated mice by tail transection with or without pretreatment with potential reversal agents: prothrombin complex concentrate (PCC); activated PCC (APCC); recombinant factor VIIa (rFVIIa); or murine fresh-frozen plasma (FFP).

METHODS

CD1 mice were given warfarin or DE by gavage, and the effects on in vitro coagulation assays, volume of blood loss and the bleeding time following tail transection injury were evaluated with different reversal agents.

RESULTS

PCC (14.3 IU kg(-1) ), but not rFVIIa (3 mg kg(-1) ) or FFP (12 mL kg(-1) ), normalized blood loss and bleeding time in mice with warfarin-induced elevations of mean prothrombin time at two intensities (prothrombin time ratios of either 4.3 or 24). Neither separate nor combined PCC and/or rFVIIa treatment nor APCC (100 U kg(-1) ) treatment significantly reduced blood loss in mice anticoagulated with 60 mg kg(-1) DE 75 min prior to tail transection. Both combined PCC plus rFVIIa treatment and APCC treatment significantly reduced bleeding time in the DE-treated mice.

CONCLUSIONS

Our data suggest that PCC treatment prevents excess bleeding much more effectively in warfarin-induced coagulopathy than in DE-induced coagulopathy.

Practical management of anticoagulants in family medicine after orthopedic surgery

In order to prevent postoperative venous thromboembolism, prophylactic anticoagulant therapy is routinely administered to hospitalized patients after total hip arthroplasty (THA) and total knee arthroplasty (TKA). However, after hospital discharge, anticoagulant therapy is primarily managed by a primary care physician (PCP). The agents traditionally used for this purpose are associated with certain limitations that affect anticoagulation management. The new, fixed-dose oral anticoagulants have predictable pharmacokinetic and pharmacodynamic profiles, no requirement for coagulation monitoring, and a low propensity for food and drug interactions. As a result, they have the potential to simplify and improve postoperative outcomes in patients who have undergone THA or TKA and allow for simpler management of anticoagulation in these patients. This article examines the clinical evidence for benefits of the new oral anticoagulants, discusses caveats regarding their appropriate use, and provides some guidance regarding bleeding management with these agents.

Systematic review and adjusted indirect comparison meta-analysis of oral anticoagulants in atrial fibrillation

BACKGROUND

Oral anticoagulants such as apixaban, dabigatran, and rivaroxaban are alternatives to warfarin for preventing events in patients with atrial fibrillation. Direct comparative studies between agents are unavailable. Our objective was to conduct an adjusted indirect comparison meta-analysis between new oral agents in atrial fibrillation.

METHODS AND RESULTS

We searched MEDLINE and Cochrane Central through February 2012 for randomized, controlled trials in patients with atrial fibrillation evaluating apixaban, dabigatran, or rivaroxaban versus warfarin. For dabigatran, only data from the Food and Drug Administration-approved dose were included. Outcomes included the composite of stroke or systemic embolism, any stroke, and major bleeding among, others. Outcomes were initially pooled using standard random-effects methods, producing risk ratio and 95% confidence intervals. Adjusted indirect comparisons using these pooled estimates were then performed. A total of 44 733 patients from 4 studies were analyzed. Most analyses yielded no differences between agents. Dabigatran lowered risk of composite outcome (risk ratio, 0.75; 95% confidence interval, 0.57-1.00), ischemic stroke (0.67; 0.48-0.93), and hemorrhagic stroke (0.45; 0.45-0.99) versus rivaroxaban. No differences in all strokes or mortality were seen. Apixaban lowered the risk of major bleeding (0.74; 0.60-0.91) and gastrointestinal bleeding (0.58; 0.41-0.82) versus dabigatran and major bleeding versus rivaroxaban (0.68; 0.55-0.83), but increased systemic emboli versus rivaroxaban (3.86; 1.17-12.75).

CONCLUSIONS

Significant differences in efficacy and safety parameters may exist between oral anticoagulant agents in patients with atrial fibrillation. Apixaban lowers the risk of major and gastrointestinal bleeding versus dabigatran and rivaroxaban. Dabigatran lowers the composite of stroke or systemic emboli, and ischemic stroke versus rivaroxaban. Head-to-head clinical trials are required to confirm these findings.

Intracerebral hemorrhage: a review of coagulation function

Intracerebral hemorrhage (ICH) is associated with a higher mortality rate among stroke subtypes. The amount of hematoma at baseline and subsequent expansion are considered strong independent markers for determining poor clinical outcome. Even though reduction in blood pressure to prevent and control the amount of bleeding in ICH has received considerable amount of attention, the impact of coagulopathy and platelet dysfunction, on the bleeding diathesis has not been extensively investigated. With the increasing use of antiplatelets and/or anticoagulants, given the aging population, a deeper understanding of the interactions between ICH and hemostatic mechanisms is essential to help minimize the risk of a catastrophic coagulopathy-related ICH. In this review article, etiology and risk factors associated with coagulopathy-related ICH are discussed. An overview of coagulation abnormalities, hemostatic agents, and blood biomarkers pertaining to ICH is included.

Anticoagulation in atrial fibrillation: the present and the future

Atrial fibrillation (AF) is the most common form of cardiac arrhythmia and associated with significant mortality and morbidity. It is a powerful predictor of future embolic stroke, such that anticoagulation is recommended in the majority of patients. For many years this has predominantly been in the form of vitamin K antagonists. However, there are well-documented difficulties with their administration that result in poor compliance and high discontinuation rates. Over recent years several oral alternative anticoagulant agents have become available with the potential to overcome many of these pitfalls. In this review, we discuss current recommendations for anticoagulant therapy in AF and how these may change in the future with the introduction of novel therapeutic options.

Reversal of drug-induced anticoagulation: old solutions and new problems

Anticoagulant drugs are taken by millions of patients throughout the world. Warfarin has been the most widely prescribed anticoagulant for decades. In recent years, new oral anticoagulants have been approved for use, are being positioned as alternatives to warfarin, and represent an enormous market opportunity for pharmaceutical companies. Requests for urgent reversal of anticoagulants are not uncommon especially in the setting of critical bleeding. This review summarizes information on reversal of warfarin by vitamin K, plasma, prothrombin complex concentrates, and recombinant VIIa. In addition, we emphasize the lack of current evidence supporting reversibility of the new oral direct thrombin inhibitors and Factor Xa inhibitors. This review is presented to assist transfusion medicine specialists, hematologists, and other clinicians who prescribe blood components for reversal of drug-induced anticoagulation.

Novel drugs for oral anticoagulation pharmacotherapy

Long-term anticoagulation with warfarin is the mainstay of treatment in patients with diseases with high thromboembolic potential, such as atrial fibrillation. However, warfarin therapy carries a number of inherent limitations, including slow onset and offset of action, interindividual variability, food and drug interactions, lack of selectivity and a narrow therapeutic window. Recently developed oral anticoagulants that selectively block key factors in the coagulation cascade, with no need for monitoring or dose adjustment, have the potential to replace warfarin in clinical practice. The safety and efficacy of these agents in patients with atrial fibrillation, venous thromboembolisms and acute coronary syndromes have been the object of numerous recent large-scale clinical investigations. This article provides an overview of the evidence currently available on the use of novel, orally available, selective anticoagulants in patients at risk for thromboembolic events.

The promise of novel direct oral anticoagulants

The standard effective treatment of venous and arterial thromboembolism includes unfractionated and low-molecular weight heparin as well as warfarin, which have major disadvantages. In recent years, new anticoagulants have been developed in an attempt to overcome the known limitations of established treatment and develop improved therapies. This chapter reviews pharmacological properties of the new anticoagulants, the most recent trials assessing their safety and efficacy as well as potential advantages and disadvantages of using these novel drugs in real life.

Dabigatran etexilate: a review of its use for the prevention of venous thromboembolism after total hip or knee replacement surgery

Dabigatran etexilate (Pradaxa®, Pradax™, Prazaxa®) is indicated for the primary prevention of venous thromboembolic (VTE) events in adults who have undergone elective total hip replacement (THR) or total knee replacement (TKR) surgery. This article reviews the clinical efficacy and tolerability of oral dabigatran etexilate in patients undergoing major orthopaedic surgery, as well as summarizing its pharmacological properties and results of a cost-utility analysis. The discussion of clinical trial data focuses on comparative trials with the EU approved dosage regimen of once-daily subcutaneous enoxaparin sodium 40 mg. Dabigatran etexilate is an oral prodrug of the potent, rapidly acting, reversible, competitive inhibitor of thrombin, dabigatran. Dabigatran has predictable and consistent anticoagulant effects and does not require routine coagulation monitoring or dose titration. In the large, randomized, double-blind, phase III, noninferiority trials, RE-MODEL, RE-NOVATE and RE-NOVATE II, oral dabigatran etexilate, at dosages of 150 and 220 mg once daily, initiated postoperatively was shown to be noninferior to subcutaneous enoxaparin sodium 40 mg once daily (initiated prior to surgery) with regard to the incidence of the composite of total VTE events and all-cause mortality in patients undergoing TKR or THR surgery. In general, oral dabigatran etexilate was well tolerated in clinical trials of patients undergoing major orthopaedic surgery. There were no significant between-group differences in bleeding complications, including major bleeding, clinically relevant non-major bleeding or minor bleeding between the dabigatran etexilate or enoxaparin sodium groups. In addition, a cost-utility analysis from the perspective of the UK National Health Service indicated that dabigatran etexilate 220 mg once daily is dominant (i.e. more effective and less costly) to enoxaparin sodium 40 mg once daily in patients undergoing THR or TKR. Additional head-to-head comparisons would be beneficial to more definitively position dabigatran etexilate relative to other available oral treatment options for VTE prophylaxis, such as rivaroxaban and apixaban. In the meantime, dabigatran etexilate offers a convenient, effective and generally well tolerated treatment option for the prophylaxis of VTE in patients undergoing TKR and THR surgery.

Current approaches to anticoagulation for reducing risk of atrial fibrillation-related stroke

Stroke is a major cause of death and disability and, as such, is associated with a heavy socioeconomic burden. Atrial fibrillation (AF) is an independent risk factor for ischemic stroke, and AF-related stroke tends to be more severe and poses a higher risk of recurrence than non-AF-related stroke. Anticoagulant prophylaxis with warfarin is effective in preventing stroke in eligible patients with AF, but in real-world practice this agent, though inexpensive, is underutilized. Moreover, warfarin has notable drawbacks that result in suboptimal anticoagulation and, as a result, greater disease burden and higher costs. Newer oral antithrombotic drugs with a wide therapeutic window and no requirement for routine coagulation monitoring may be as efficacious as warfarin and, given the costs associated with managing warfarin therapy, they may also prove to be more cost effective.

Emergency management of bleeding associated with old and new oral anticoagulants

As major prescribers of oral anticoagulants, cardiologists must be familiar with strategies to manage bleeding, the principal complication associated with all anticoagulants, and to reverse anticoagulant effects in acute-care settings. The purpose of this manuscript is to review currently available information regarding dabigatran and rivaroxaban, the 2 novel oral anticoagulants approved to date in the United States. Further, we suggest reasonable interventions for the clinician faced with a patient who suffers a major bleeding event while receiving one of these agents. Data sources were peer-reviewed publications, US Food and Drug Administration documents in the public domain, and approved US prescribing information for dabigatran (Pradaxa) and rivaroxaban (Xarelto). Strategies for management of bleeding and reversal of anticoagulant effects from warfarin include vitamin K, fresh frozen plasma, and prothrombin complex concentrates. For rivaroxaban and dabigatran, appropriate therapies include support and observation, which are likely to be effective for the majority of patients because of the short half-lives of these agents. In severe life-threatening hemorrhage, clotting-factor substitutes may be appropriate in certain situations. Validated protocols specific to each agent remain to be developed.

Safety and efficacy of apixaban in the treatment of atrial fibrillation

Atrial fibrillation is a common arrhythmia that increases the risk of stroke and systemic embolism. Warfarin is a highly effective treatment in reducing this risk, but a narrow therapeutic range, drug and food interactions, required monitoring, and bleeding limit its use. We review Apixaban, an oral inhibitor of Factor Xa, which has been shown in large randomized trials to have superior efficacy in stroke reduction without an excess in bleeding events when compared with aspirin in those deemed unsuitable to receive warfarin, and demonstrates superior efficacy in reducing stroke and systemic embolism in addition to a reduction in bleeding events when compared to warfarin.

[New oral anticoagulants. Significance for dermatology and phlebology]

Venous thromboembolism and atrial fibrillation are common and are treated with vitamin K antagonists in 1.7% of the total population in the western world. The limitations of the vitamin K antagonists and of heparin have led to the development of new oral drugs. These drugs inhibit thrombin or factor Xa and can be given in a fixed dosage; they have a broad therapeutic margin and relatively few drug interactions. Specific risks and problems also are associated with the new drugs such as interference with common coagulation tests without being able to draw any conclusion as to the actual bleeding risk and the lack of specific antidotes. No established coagulation monitoring is available. The article gives reviews the current knowledge and provides practical advice on how to use the new drugs for the approved indications such as knee and hip replacement, therapy of deep venous thrombosis and of atrial fibrillation. Beyond that, recommendations are given for perioperative management and for change of treatment.

Advances in oral anticoagulation treatment: the safety and efficacy of rivaroxaban in the prevention and treatment of thromboembolism

Arterial and venous thromboembolic diseases are a clinical and economic burden worldwide. In addition to traditional agents such as vitamin K antagonists and heparins, newer oral agents – such as the factor Xa inhibitors rivaroxaban, apixaban, and edoxaban, and the direct thrombin inhibitor dabigatran – have been shown to be effective across several indications. Rivaroxaban has been shown to have predictable pharmacokinetic and pharmacodynamic properties, including a rapid onset of action. In addition, there is no requirement for routine coagulation monitoring; and no dose adjustment is necessary for age alone, sex, or body weight. Rivaroxaban has successfully met primary efficacy and safety endpoints in large, randomized phase III trials across several indications, including: prevention of venous thromboembolism in orthopedic patients undergoing elective hip or knee replacement surgery; treatment of deep vein thrombosis and secondary prevention of deep vein thrombosis and pulmonary embolism; stroke prevention in patients with atrial fibrillation; and secondary prevention of acute coronary syndrome. Rivaroxaban and the other newer oral anticoagulants are likely to improve outcomes in the prevention and treatment of thromboembolic events, and will offer patients and physicians alternative treatment options.

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

To date, clinical studies show that the incidence of spontaneous bleeding with new direct oral anticoagulants (DOAs) is comparable to that of established anticoagulants. However, unlike vitamin K antagonists, there are currently no clinically available antidotes or approved reversal agents for new DOAs. Restoring normal coagulation is important in many cases, such as emergency surgeries, serious bleedings, or anticoagulant overdosing. Attempts have been made to restore normal coagulation after treatment with new DOAs using compounds such as recombinant activated factor VII (rFVIIa), prothrombin complex concentrate (PCC), or FEIBA (factor eight inhibitor bypassing activity). Limited pre-clinical data and even less clinical evidence are available on the usefulness of these methods in restoring normal coagulation for the emergency management of critical bleeding episodes. Evaluating the utility of DOAs is further complicated by the fact that it is unknown how predictive established test systems are of the bleeding risks. Clinical practice requires further evaluation of the emergency management options for the new DOAs to define the agents and the doses that are most useful. Furthermore, patients receiving long-term treatment with a DOA are likely to undergo elective surgery at some point, and there is lack of evidence regarding perioperative treatment regimens under such conditions. This review summarises potential bleeding management options and available data on the new DOAs.

Promise and challenges of anticoagulation with dabigatran

Dabigatran, marketed as Pradaxa (Boehringer Ingelheim) in the USA, is a direct thrombin inhibitor that holds great promise. It has been shown to reduce the risk of stroke and venous thromboembolism with similar if not greater efficacy than warfarin and with far fewer side effects. However, like other anticoagulants, it can cause severe bleeding complications and lacks a specific antidote with proven efficacy. The patient presented here was on dabigatran and sustained a traumatic intracranial hemorrhage (ICH). The ICH continued to progress despite prompt initiation of 3h of hemodialysis in an effort to remove the offending drug from the circulation. Through this case report, we highlight the challenges of anticoagulation with dabigatran including the lack of routine testing for monitoring its effect and of a specific antidote. We also discuss the potential role of dialysis in treating patients with life-threatening bleeding on dabigatran.

Current Issues in Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia. It places an enormous burden on the patients, caregivers, and the society at large. While the main themes in the care of an AF patient have not changed over the years and continue to focus on stroke prevention, control of the ventricular, rate and rhythm maintenance, there have been a number of new developments in each of these realms. This paper will discuss the “hot” topics in AF in 2012 including new and upcoming medical and invasive management strategies for this condition.

Dabigatran: a primer for neurosurgeons

OBJECTIVE

This study sought to present an overview of dabigatran, a new anticoagulant, and to discuss the implications for the perioperative management of patients taking dabigatran.

METHODS

We reviewed the English literature pertaining to the new oral anticoagulant, dabigatran (Pradaxa).

RESULTS

Dabigatran has the advantage of providing rapid and steady anticoagulation without requiring laboratory monitoring. However, the fact that no practical, reliable method of monitoring of the anticoagulant effects is available constitutes a challenge when contemplating urgent neurosurgical procedures in patients treated with this medication. Although the risk of intracranial hemorrhage with dabigatran was lower than with warfarin in the large trial leading to the approval of the drug, the management of these complications may be problematic because there is no current antidote.

CONCLUSIONS

We present a basic overview of dabigatran, discuss the implications for the perioperative management of patients taking this new anticoagulant, and offer recommendations for the management of intracranial hemorrhage related to this drug.

More light at the end of the tunnel - apixaban in atrial fibrillation

INTRODUCTION

Subjects with atrial fibrillation are at risk of thromboembolic events. The vitamin K antagonists (e.g., warfarin) are useful at preventing coagulation in atrial fibrillation, but are difficult to use. One of the FXa inhibitors, oral apixaban, has been tested as an anticoagulant in atrial fibrillation.

AREAS COVERED

In ARISTOTLE (Apixaban for reduction in stroke and other thromboembolic events in atrial fibrillation) apixaban was compared to warfarin in subjects with atrial fibrillation, and shown to cause a lower rate of stroke or systemic embolism and of major bleeding, than warfarin. In the AVERROES (Apixaban versus acetylsalicylic acid [ASA] to prevent stroke in atrial fibrillations patients who have failed or are unsuitable for vitamin K antagonist treatment) trial, stroke or systemic embolism occurred less often with apixaban than aspirin, whereas the occurrence of major bleeding was similar in the groups.

EXPERT OPINION

Apixaban is much easier for subjects with atrial fibrillation to use than warfarin, as it does not require regular monitoring by a health professional, with dosage adjustment. In addition to replacing warfarin in subjects with atrial fibrillation who are unable or not prepared to use warfarin, apixaban has the potential to replace warfarin more widely in the prevention of thromboembolism in subjects with atrial fibrillation.

Rectal bleeding and hemostatic disorders induced by dabigatran etexilate in 2 elderly patients

OBJECTIVE

To report rectal bleeding associated with hemostatic disorders in 2 elderly patients treated with dabigatran etexilate.

CASE SUMMARY

A 79-year-old woman (weight, 69 kg) was hospitalized in a gastroenterology unit for severe rectal bleeding. She had been treated for 2 months with dabigatran etexilate 110 mg twice daily for chronic atrial fibrillation. On admission, her creatinine clearance (CrCl) was 20.7 mL/min/1.73 m(2), prothrombin time (PT) less than 10% (reference range 70-130%), and international normalized ratio (INR) 14.5 (venous blood). Eleven days after admission, hematologic and renal function were normalized and rectal bleeding stopped. An 84-year-old man (weight, 71 kg) was admitted for rectal bleeding with acute renal failure and dehydration that began while he was treated with dabigatran etexilate 110 mg twice daily for atrial fibrillation. On admission, CrCl was 33.5 mL/min/1.73 m(2), PT 13%, and INR 7.53 (venous blood). Dabigatran etexilate was stopped on admission. At the end of the hospitalization, CrCl was 66.5 mL/min/1.73 m(2), PT 54%, and INR 1.53. In both cases, an objective causality assessment revealed that those adverse reactions were probably related to dabigatran etexilate.

DISCUSSION

In these 2 cases of rectal bleeding during dabigatran etexilate therapy, coagulation monitoring showed elevated PT and INR; neither patient had been exposed to vitamin K antagonists. These cases indicate the importance of PT and INR monitoring when using dabigatran etexilate, mainly in patients with a high risk of overdose, such as elderly patients or those with renal function impairment.

CONCLUSIONS

It is critical to identify and subsequently manage dabigatran etexilate toxicity because there is no specific antidote to reverse the drug's anticoagulant effects.

Rationale and design of XAMOS: noninterventional study of rivaroxaban for prophylaxis of venous thromboembolism after major hip and knee surgery

Venous thromboembolism is a frequent and potentially life-threatening complication of orthopedic surgery. Rivaroxaban is an oral direct factor Xa inhibitor, which was shown to be effective for the prevention of venous thromboembolism after elective hip and knee arthroplasty in the RECORD study program. Rivaroxaban has the potential to overcome the limitations of the current standards of care in the prevention of venous thromboembolism. XAMOS (Xarelto^® in the prophylaxis of post-surgical venous thromboembolism after elective major orthopedic surgery of hip or knee) is an international, noninterventional, parallel-group study to gain insight into the safety (major bleeding, side effects) and effectiveness (prevention of symptomatic thromboembolic events) of rivaroxaban in daily clinical practice. XAMOS will follow 15,000 patients after major orthopedic surgery in approximately 200 centers worldwide, with about 7500 patients receiving rivaroxaban and about 7500 standard of care. XAMOS will supplement the clinical data obtained in the Phase III RECORD 1, 2, 3, and 4 trials in which rivaroxaban was shown to be superior for the primary efficacy endpoints, and with a safety profile similar to that of enoxaparin after hip or knee replacement surgery. XAMOS was started in 2009 and will complete recruitment and follow-up in 2011.

[Management of direct action oral anticoagulants in the peri-operative period and invasive techniques]

The new direct-acting oral anticoagulants (ACOD) in patients on prolonged treatment require the need to balance the risk of haemorrhage by administering them against the risk of thrombosis on withdrawing them. Recommendations for their management are proposed in the present article: A) Thromboprophylaxis and general anaesthesia: the performing of regional anaesthesia if administered with an ACOD as thromboprophylaxis requires some safety intervals based on their pharmacokinetic parameters; B) Management of ACOD in elective surgery: in patients with normal renal function and a low haemorrhage/thrombosis risk, stop the ACOD two days before the surgery; it the haemorrhage/thrombosis risk is high and/or renal function is impaired, therapy with a low molecular weight heparin is proposed from 5 days prior to the surgery, and C) Management of ACOD in urgent surgery and associated haemorrhage: the systematic prophylactic administration of haemostatics is recommended. In the event of acute bleeding that may place the life of the patient at risk (due to volume or location), the administration of concentrated prothrombin complex, fresh plasma, or factor VIIa, must be assessed, together with general control measures of acute haemorrhage. These recommendations should be considered in the context of the use drugs that do have a specific antidote, where their monitoring by the usual coagulation tests is not routine, and with those in which there is limited experience. We believe they need to be reviewed in the future, depending on further studies and clinical experience obtained.

Rivaroxaban, an oral, direct factor Xa inhibitor: a new option for thromboprophylaxis

Patients undergoing major orthopedic surgery, including total hip arthroplasty (THA) and total knee arthroplasty (TKA), are at high risk for developing venous thromboembolism (VTE). Although largely a preventable complication, VTE develops in a significant proportion of patients, highlighting the need for improved methods of VTE prevention. Current thromboprophylactic options are limited by unpredictable pharmacokinetics and pharmacodynamics (vitamin K antagonists), parenteral/subcutaneous administration (heparin and low-molecular-weight heparins), complicated dosing, and increased risk of bleeding.Rivaroxaban is an oral, direct Factor Xa inhibitor that has recently received marketing authorization in the United States for prophylaxis of deep vein thrombosis in patients undergoing hip or knee replacement surgery. The clinical pharmacology of rivaroxaban supports a convenient, oral, once-daily dosing regimen without the need for routine coagulation monitoring after THA or TKA. A comprehensive phase II and III study program supports its safety and efficacy for VTE prevention after THA or TKA. Phase III results have demonstrated the superior efficacy of rivaroxaban regimens compared with enoxaparin regimens, with similar rates of major bleeding. This article provides an overview of the phase II and III results that support the use of this agent for the prevention of VTE after elective total hip or knee replacement.

Novel oral anticoagulants for stroke prevention in atrial fibrillation: focus on apixaban

Stroke prevention in atrial fibrillation (AF) has been challenging over decades, mostly due to a number of difficulties associated with oral vitamin K antagonists (VKAs), which have been the most effective stroke prevention treatment for a long time. The oral direct thrombin inhibitors (e.g., dabigatran) and oral direct inhibitors of factor Xa (e.g., rivaroxaban, apixaban) have emerged recently as an alternative to VKAs for stroke prevention in AF. These drugs act rapidly, and have a predictable and stable dose-related anticoagulant effect with a few clinically relevant drug-drug interactions. The novel oral anticoagulants are used in fixed doses with no need for regular laboratory monitoring of anticoagulation intensity. However, each of these drugs has distinct pharmacological properties that could influence optimal use in clinical practice. The following phase 3 randomized trials with novel oral anticoagulants versus warfarin for stroke prevention in AF have been completed: the Randomized Evaluation of Long-term Anticoagulant therapy (RE-LY) trial with dabigatran, the Rivaroxaban Once daily oral direct Factor Xa inhibition Compared with vitamin K antagonism for prevention of stroke and Embolism Trial in Atrial Fibrillation (ROCKET-AF) trial with rivaroxaban, and the Apixaban for Reduction of Stroke and Other Thromboembolism Events in Atrial Fibrillation (ARISTOTLE) trial with apixaban. Moreover, the Apixaban Versus Acetylsalicylic Acid to prevent Strokes (AVERROES) trial included patients with AF who have failed or were unsuitable for warfarin, and compared apixaban versus aspirin for stroke prevention in AF. Overall, apixaban has two large trials for stroke prevention in AF showing benefits not only over warfarin, but also over aspirin among those patients who have failed or refused warfarin. In the ARISTOTLE trial, apixaban was superior to warfarin in the reduction of stroke or systemic embolism, major bleeding, intracranial hemorrhage, and all-cause mortality, with a similar reduction in the rate of ischemic stroke and better tolerability. When compared with aspirin in the AVERROES trial, apixaban was associated with more effective reduction of stroke, a similar risk of major bleeding, and better tolerability. In this review article, the authors summarize the current knowledge on novel oral anticoagulants and discuss the clinical aspects of their use for stroke prevention in AF, with particular emphasis on apixaban.

Prevention of stroke in patients with atrial fibrillation: anticoagulant and antiplatelet options

As the population ages, the prevalence of atrial fibrillation (AF) continues to rise. The most feared complication of this common cardiac arrhythmia is cardioembolic stroke. Strokes related to AF are associated with greater morbidity and mortality than ischemic strokes of most other etiologies and impose a substantial economic burden on healthcare systems around the world. Until recently, warfarin was the sole anticoagulant proven effective for stroke prevention patients with AF at elevated risk, but its narrow therapeutic margin and variable dose response limited clinical utility. The emergence of new anticoagulants that offer equal or superior efficacy, greater safety and the convenience of fixed oral dosing may make warfarin the less preferred option. This review provides an update on recent advancements in antithrombotic therapy for stroke prevention in patients with AF.

Breakthroughs in anticoagulation: advent of the oral direct factor Xa inhibitors

The oral direct factor Xa inhibitors include rivaroxaban and apixaban that recently have been evaluated comprehensively in multiple randomized clinical trials. Based on the efficacy and safety data from these trials, these novel anticoagulants are disseminating throughout clinical practice for thromboprophylaxis in major lower-extremity joint replacement, acute medical illness, atrial fibrillation, and acute coronary syndromes. The advantages of the xabans over vitamin K antagonists include no requirement for routine anticoagulation monitoring as well as a fast and reliable onset of action. The first perioperative limitation of the xabans is the lack of a routine coagulation test for monitoring their anticoagulant effect in scenarios, such as the timing of surgical procedures, the reversal of xaban-related bleeding, and the conduct of regional anesthesia. A second perioperative limitation is the lack of fully validated clinical reversal agents although prothrombin complex concentrate, recombinant factor VIIa, and factor X concentrate are options for xaban reversal in life-threatening bleeding scenarios. Given their clinical efficacy and advantages, further xabans are in clinical development, with edoxaban already in phase III clinical trials. Although the xabans have ushered in a new paradigm for clinical anticoagulation, further clinical trials are indicated to refine their clinical indications even further, such as anticoagulation for patients with mechanical heart valves.

Pharmacokinetic evaluation of rivaroxaban for the treatment of acute coronary syndromes

INTRODUCTION

Arterial and venous thrombotic states, including myocardial infarction (MI), stroke and deep vein thrombosis with subsequent pulmonary embolism, are a significant cause of cardiovascular mortality and morbidity. Factor Xa (FXa) plays a pivotal role in thrombus formation. Its inhibition following acute coronary syndromes (ACS) blocks amplification of thrombin generation and subsequent clot formation, resulting in a risk reduction in recurrent MI, stroke and death. For this reason, a predictable form of oral anticoagulation continues to be an ongoing need. Rivaroxaban , the first oral FXa inhibitor, acts by direct inhibition of FXa and does not require an antithrombin cofactor for its activity.

AREAS COVERED

This paper describes the pharmacokinetics (PK) of low-dose rivaroxaban tested in patients with ACS. Age, gender, renal function and body weight have no clinically significant effects on the PK of the drug in treatment of ACS. Caution should be maintained during co-administration of strong CYP3A4 inducers and inhibitors. Among patients with moderate and severe hepatic impairment and in those with associated coagulopathies, rivaroxaban however is contraindicated.

EXPERT OPINION

The mortality benefit with low-dose rivaroxaban in ACS patients was first demonstrated in ATLAS ACS2 TIMI-51 trial. With its rapid oral bioavailability, predictable PK, low drug-drug interaction and no need for monitoring, the use of low-dose rivaroxaban in addition to dual antiplatelet therapy offers an appealing new option in improving outcomes following ACS in the modern era of novel oral FXa inhibitors.

Acute-onset severe gastrointestinal tract hemorrhage in a postoperative patient taking rivaroxaban after total hip arthroplasty: a case report

INTRODUCTION

Rivaroxaban, a new oral anticoagulant, is currently licensed for use in patients undergoing orthopedic surgery. It is more efficacious than other anticoagulants such as low molecular weight heparin and does not require daily monitoring. It has also been shown to be efficacious in patients with venous thromboembolism and acute coronary syndrome. Although hemorrhage is a known side effect of this new anticoagulant, we could find no case reports in the literature of patients suffering severe hemorrhage whilst taking rivaroxaban. Thus, we describe the first case of potentially fatal hemorrhage in a patient taking rivaroxaban.

CASE PRESENTATION

We report the case of a 58-year-old Caucasian man with acute-onset severe per rectal bleeding who had undergone total hip arthroplasty four weeks prior to the onset of symptoms and was taking rivaroxaban in the postoperative period. Rivaroxaban was discontinued immediately but, having required nine units of packed red blood cells in a peripheral hospital due to a rapidly decreasing hemoglobin level, our patient was transferred to our tertiary referral center where he required a further eight units of packed red blood cells over a 48-hour period to manage his ongoing hemorrhage and maintain hemodynamic stability. No source of bleeding was found on computed tomography angiography and our patient's condition improved over the following 48 hours with cessation of the hemorrhage. Our patient was discharged home well several days later. A follow-up colonoscopy one week after his discharge was normal.

CONCLUSION

Although advantageous with regard to its oral availability and ongoing use without the need for daily monitoring, rivaroxaban does not come without rare but severe side effects. When severe per rectal bleeding occurs in a patient taking rivaroxaban, discontinuation of the offending agent and aggressive hematological replacement are the mainstays of treatment, especially when no source of bleeding can be found. This case, as the first to describe severe hemorrhage and rivaroxaban, serves as a reminder to those prescribing the medicine that they must inform the patient of the risk of such a serious side effect and the need for urgent medical attention if it occurs.