Apixaban or enoxaparin for thromboprophylaxis after knee replacement

The effect of apixaban on the pharmacokinetics of digoxin and atenolol in healthy subjects

Purpose

Apixaban is often coadministered with treatments for cardiovascular comorbidities, which may lead to unintended drug–drug interactions (DDIs). The effects of apixaban on pharmacokinetics (PK) of multidose Lanoxin^® (digoxin) and single-dose Tenormin^® (atenolol) and the effects of single-dose atenolol on apixaban PK in healthy subjects were investigated in two Phase 1 studies.

Patients and methods

The digoxin DDI study was an open-label, multidose, two-treatment, single-sequence study in which subjects received digoxin 0.25 mg q6h on day 1, then once daily on days 2–10, followed by apixaban 20 mg and digoxin 0.25 mg once daily on days 11–20. The atenolol DDI study was an open-label, single-dose, randomized, three-period, three-treatment, crossover study in which subjects received a single oral dose of apixaban 10 mg, atenolol 100 mg, or apixaban 10 mg plus atenolol 100 mg. The 90% confidence intervals (CIs) for the ratios of geometric means of peak plasma concentration (C_max) and area under the concentration–time curve (AUC_tau), with and without apixaban were calculated. Absence of effect was concluded if the point estimates and 90% CI were within the equivalence interval of 80%–125% (digoxin) or 70%–143% (atenolol). A similar analysis was performed to assess the effect of atenolol on apixaban.

Results

Apixaban had no clinically relevant effect on the PK of either atenolol or digoxin: point estimates and 90% CI for both digoxin and atenolol C_max and AUC were entirely within their respective no-effect intervals. Apixaban C_max and AUC_inf were slightly decreased (ie, 18% and 15% lower, respectively) following atenolol coadministration. No serious or major bleeding-related adverse events were reported during either study.

Conclusion

Apixaban had no effect on the PK of digoxin and there was no clinically relevant interaction between apixaban and atenolol. Coadministration of digoxin or atenolol with apixaban in healthy subjects was generally well tolerated.

Safety and Efficacy of New Anticoagulants for the Prevention of Venous Thromboembolism After Hip and Knee Arthroplasty: A Meta-Analysis

BACKGROUND

Venous thromboembolism (VTE) is a common and potentially fatal complication of arthroplasty.

METHODS

We reviewed randomized trials to determine which anticoagulant has the best safety and efficacy in hip and knee arthroplasty patients. We searched PubMed, MEDLINE, and EMBASE through January 2016.

RESULTS

Compared to enoxaparin (most commonly dosed 40 mg once daily), the relative risk (RR) of VTE was lowest for edoxaban 30 mg once daily (0.49; 95% confidence interval [CI], 0.32-0.75), fondaparinux 2.5 mg once daily (0.53; 95% CI, 0.45-0.63), and rivaroxaban 10 mg once daily (0.55; 95% CI, 0.46-0.66), and highest for dabigatran 150 mg once daily (1.19; 95% CI; 0.98-1.44). The RR of major/clinically relevant bleeding was lowest for apixaban 2.5 mg twice daily (0.84; 95% CI; 0.70-0.99) and highest for rivaroxaban (1.27; 95% CI, 1.01-1.59) and fondaparinux (1.64; 95% CI, 0.24-11.35). Fondaparinux was the only agent that was more effective than enoxaparin 30 mg twice daily (VTE RR = 0.58; 95% CI, 0.43-0.76).

CONCLUSION

With the possible exception of apixaban, newer anticoagulants that lower the risk of postoperative VTE increase bleeding.

Assessment of Patient Adherence to Direct Oral Anticoagulant vs Warfarin Therapy

CONTEXT

Direct oral anticoagulants (DOACs) may be as effective as, and at times safer than, warfarin. Because DOACs do not require regular serum level monitoring, patients' interaction with the health care system may be reduced. To the authors' knowledge, although studies have evaluated warfarin adherence, few studies have evaluated the real-world adherence to DOACs.

OBJECTIVE

To evaluate whether a difference exists between medication adherence of patients taking DOACs vs patients taking warfarin.

METHODS

The electronic medical records of the Anticoagulation Clinic database at Mayo Clinic in Scottsdale, Arizona, were reviewed. Inclusion criteria were adults taking DOACs and a matching cohort taking warfarin between January 1, 2011, and December 30, 2013. The Morisky Medication Adherence Scale-8 item, a validated medication adherence tool, was used to evaluate adherence in both cohorts, and the qualitative covariates were analyzed using ordinal logistic regression.

RESULTS

Of 324 surveys that were sent, 110 patients (34.0%) responded. Most patients took DOACs for atrial fibrillation, and few took DOACs for venous thromboembolism. Overall, 60 of 66 patients (90.9%) in the DOAC group and 42 of 44 patients (95.5%) in the warfarin group reported medium or high adherence. Difference in adherence scores between the 2 groups was not statistically significant (P=.8).

CONCLUSION

Similar adherence was noted between DOACs and warfarin regardless of the frequency of serum level monitoring.

Perioperative Management of Anticoagulation-Review of Latest Evidence

Periprocedural anticoagulation bridging is recommended to reduce the risk of thromboembolic events in patients at a higher risk of developing thromboembolism during the perioperative period. The optimal periprocedural anticoagulation strategy has not been established. Unfractionated heparin and low molecular heparin are used in preventing thromboembolism in the special population. Novel oral anticoagulants that directly inhibit thrombin (dabigatran) or factor Xa (rivaroxaban, apixaban) are shown as effective anticoagulants in preventing thromboembolism (venous thromboembolism) in various medical conditions. They have the advantage of having a faster onset, shorter half-lives, easier monitoring, and predicable doses. But there are disadvantages to newer anticoagulants such as the unavailability of definitive reversal agents and lack of data in patients with renal insufficiency. We review the latest evidence on the effects of newer oral anticoagulants in preventing thromboembolism and its bleeding risks.

A review of the fixed dose use of new oral anticoagulants in obese patients: Is it really enough?

Obesity is a significant cause of morbidity and mortality, and it is becoming increasingly prevalent worldwide. Altered pharmacodynamics and pharmacokinetics of drugs in obese patients require dose adjustment according to body weight. New oral anticoagulants (NOACs), which are more frequently used for anticoagulation, are recommended to be used at a fixed dose based on data derived from phase 2 and 3 studies. However, the representation of obese patients [>100 kg or a body mass index (BMI) of >30 kg/m²] in subgroups with a small sample size and reports of various emboli cases under drug treatment have raised suspicions about the adequacy of fixed dose use. To address this issue, we analyzed several patients with a body weight of >100 kg or BMI of >30 kg/m² participating in NOAC studies and evaluated whether these numbers were sufficient to enable an accurate recommendation of fixed dose use in obese patients.

Use of novel oral anticoagulant agents in venous thromboembolism

New oral anticoagulants (NOAC) serve as alternatives for patients currently using warfarin for the prevention and treatment of venous thromboembolic (VTE) disease. This article provides a brief summary of the clinical use of these drugs as well as a review of the landmark clinical trials which evaluated described their safety and efficacy. As more data becomes available, a fundamental understanding of these medications will be vital to cardiovascular practitioners managing patients with VTE.

An update on the pharmaceutical management of thrombosis

INTRODUCTION

Anticoagulants such as heparins and vitamin K antagonists (VKA) are effective for thrombosis prevention and treatment, but are associated with the risk of bleeding and other limitations, spurring the search for improved drugs. Areas covered: to evaluate the newer anticoagulants, focusing on those tested in phase III clinical trials such as direct oral anticoagulants (DOACs), antisense oligonucleotides (ASO) and warfarin analogues. DOACs such as dabigatran, rivaroxaban, apixaban and edoxaban are licensed for stroke prevention in atrial fibrillation and treatment of venous thromboembolism, dabigatran, rivaroxaban and apixaban for postoperative thromboprophylaxis in patients undergoing elective hip or knee arthroplasty and rivaroxaban for secondary prevention of acute coronary syndromes. ASO interfering with Factor XI hepatic synthesis were effective and safe for thromboprophylaxis in elective knee arthroplasty. Expert opinion: DOACs have overcome some limitations of anticoagulants such as VKA, but are still associated with a risk of bleeding and they lack both standardized and widely available tests measuring their anticoagulant effect and a reversal agent, except for idarucizumab, specific for dabigatran, in case of major or life threatening bleeding or emergency surgery. Agents targeting Factor XI and possibly Factor XII may be ideal anticoagulants, as they can prevent thrombosis with low bleeding risk.

Novel Oral Anticoagulants in Atrial Fibrillation: Update on Apixaban

Almost 800,000 new or recurrent strokes occur every year. Atrial fibrillation, the most common cardiac arrhythmia, is a major risk factor for stroke, accounting for 15-20% of ischemic strokes. Apixaban is a direct inhibitor of Factor Xa that was approved in December 2012 by the US Food and Drug Administration (FDA) for the prevention of stroke in patients with non-valvular atrial fibrillation. It is part of a family of novel oral anticoagulants (NOACs) which has advantage over warfarin of less dosing variability, rapid onset of action and no INR monitoring required. Apixaban showed superiority to warfarin in both primary efficacy and primary safety outcomes by simultaneously showing both significantly lower rates of strokes and systemic embolism and a reduced risk of major clinical bleeding in clinical trials. Warfarin remains the anticoagulant of choice for patients with prosthetic heart valves and significant mitral stenosis. There are currently no head-to-head studies that directly compare the different NOACs with one another, but it is expected that there will be more trials in the future that will explore this comparison. Dabigatran is the only NOAC with an FDA approved reversal agent. However, a reversal agent for apixaban is being developed and was successful in recent clinical trials. This review summarizes the clinical trial data on apixaban for atrial fibrillation, compares apixaban to other NOACs and discusses apixaban use in clinical practice.

Popular naturally occurring antioxidants as potential anticoagulant drugs

Blood coagulation is a physiological process whose main task is prevention of blood loss from injured vessels. This process consists of a series of zymogens proteolytic activation leading to the generation of the main coagulation enzyme - thrombin. Besides its important role in blood coagulation process, thrombin is involved in many cardiovascular diseases, which are responsible for almost half of fatalities in economically developed countries. The evidence for the increased generation and in vivo activity of thrombin was observed in the plasma of individuals at high risk for clinically significant venous and arterial thromboembolic complications. Antioxidants activity of plants extracts has been well known for many years and was confirmed by many publications. However, during the last decade many research centers presented results suggesting anticoagulant potential of various plant extracts. Many researchers have also provided evidence that polyphenol compounds are able to inhibit the activity of many enzymes, including serine proteases. All research described in this review clearly indicate that polyphenols and polyphenol-rich extracts possess not only antioxidative but also anticoagulant properties and may be useful in creation of new therapeutic agents or dietary supplements. Based on described properties polyphenols would be very helpful with both prevention and treatment of thromboembolic complications associated with multiple failures of haemostasis, because the available therapeutic agents do not offer such double-effects (antioxidant and anticoagulant).

Uso de los anticoagulantes orales directos en la práctica clínica

<p>Los anticoagulantes orales directos surgieron en respuesta a la búsqueda de un anticoagulante ideal después de que la warfarina fuera por mucho tiempo el único disponible. Los inhibidores del factor X activado —rivaroxabán y apixabán— y el inhibidor de trombina —dabigatrán etexilato— ya están aprobados en Colombia. Estos grupos farmacológicos están indicados en la tromboprofilaxis luego de artroplastia de rodilla y cadera, en la prevención del accidente cerebrovascular y el embolismo sistémico en pacientes con fibrilación auricular no valvular y en el tratamiento del tromboembolismo venoso. La aprobación de los inhibidores se dio luego de mostrar eficacia y seguridad al compararse con warfarina y enoxaparina. Entre las ventajas que estos presentan figuran las siguientes: inicio rápido de acción, efecto predecible, poca variabilidad interindividual que elimina la necesidad de la monitorización frecuente y menos interacciones medicamentosas; pero, al igual que en la warfarina, el sangrado es el principal evento adverso. El objetivo de esta revisión es conocer la farmacología de los anticoagulantes orales directos aprobados en Colombia, los resultados de los ensayos clínicos que respaldan su uso, la dosificación, el uso perioperatorio y el cambio entre anticoagulantes; situaciones que plantean particularidades para cada uno.</p>

Use of direct oral anticoagulants with regional anesthesia in orthopedic patients

The use of direct oral anticoagulants including apixaban, rivaroxaban, and dabigatran, which are approved for several therapeutic indications, can simplify perioperative and postoperative management of anticoagulation. Utilization of regional neuraxial anesthesia in patients receiving anticoagulants carries a relatively small risk of hematoma, the serious complications of which must be acknowledged. Given the extensive use of regional anesthesia in surgery and the increasing number of patients receiving direct oral anticoagulants, it is crucial to understand the current clinical data on the risk of hemorrhagic complications in this setting, particularly for anesthesiologists. We discuss current data, guideline recommendations, and best practice advice on effective management of the direct oral anticoagulants and regional anesthesia, including in specific clinical situations, such as patients undergoing major orthopedic surgery at high risk of a thromboembolic event, or patients with renal impairment at an increased risk of bleeding.

Safety and Efficacy of Novel Oral Anticoagulants vs Low Molecular Weight Heparin for Thromboprophylaxis in Large-Volume Liposuction and Body Contouring Procedures

BACKGROUND

Preventing venous thromboembolism (VTE) remains an important topic in the plastic surgery community. However, there is little consensus regarding appropriate VTE prophylaxis for patients undergoing common body contouring procedures.

OBJECTIVES

This study compared the use of two novel oral anticoagulants (Rivaroxaban and Apixiban) vs low molecular weight heparin (LMWH) for postoperative chemical prophylaxis in body contouring plastic surgery procedures.

METHODS

A single center retrospective chart review of 1572 patients who underwent body contouring plastic surgery procedures from January 2012 to February 2015 was performed. Major complications associated with chemical prophylaxis were reviewed including hematomas requiring surgical evacuation, acute blood loss anemia requiring transfusions, and thrombotic or hemorrhagic events.

RESULTS

Drug-related adverse events occurred in 1.27% (n = 20) of patients. The complications encountered by the 454 patients on LMWH consisted of 0.88% (n = 4) with hematomas requiring surgical evacuation, 0.44% (n = 2) with decreased hemoglobin requiring transfusions, and 0.22% (n = 1) with a deep vein thrombosis (DVT). The complications encountered by 703 patients on with Rivaroxaban consisted of 1.3% (n = 9) with hematomas requiring surgical evacuation, 0.43% (n = 3) with decreased hemoglobin requiring transfusions, and 0.1% (n = 1) with a DVT and pulmonary embolism. The complications encountered by 415 patients on with Apixaban consisted of 0.48% (n = 2) with a DVT.

CONCLUSIONS

Novel oral anticoagulants (Rivaroxaban and Apixiban) are comparable to LMWH for chemical prophylaxis after body contouring procedures with similar rates of drug-related complications. Further investigation is warranted with more clinical cases in order to recommend the use of this medication for routine postoperative chemical prophylaxis after body contouring procedures.

LEVEL OF EVIDENCE

3 Therapeutic.

Effect of Rifampin on the Pharmacokinetics of Apixaban, an Oral Direct Inhibitor of Factor Xa

OBJECTIVE

Apixaban is a substrate of cytochrome P450 3A4 (CYP3A4) and P-glycoprotein. The effects of rifampin, a strong inducer of CYP3A4 and P-glycoprotein, on the pharmacokinetics of oral and intravenous apixaban were evaluated in an open-label, randomized, sequential crossover study.

METHODS

Twenty healthy participants received single doses of apixaban 5 mg intravenously on day 1 and 10 mg orally on day 3, followed by rifampin 600 mg once daily on days 5-15. Finally, participants received single doses of apixaban 5 mg intravenously and 10 mg orally separately on days 12 and 14 in one of two randomized sequences.

RESULTS

Apixaban, given intravenously and orally, was safe and well tolerated when administered in the presence and absence of rifampin. Apixaban absolute oral bioavailability was 49 % when administered alone and 39 % following induction by rifampin. Rifampin reduced apixaban area under the plasma concentration-time curve from time zero to infinity (AUC∞) by 39 % after intravenous administration and by 54 % after oral administration. Rifampin induction increased mean clearance by 1.6-fold for intravenous apixaban and mean apparent clearance by 2.1-fold for oral apixaban, indicating rifampin affected both pre-systemic and systemic apixaban elimination pathways.

CONCLUSION

Co-administration of apixaban with rifampin reduced apixaban exposure via both decreased bioavailability and increased systemic clearance.

Effects of age and sex on the single-dose pharmacokinetics and pharmacodynamics of apixaban

BACKGROUND AND OBJECTIVES

The effects of age and sex on apixaban pharmacokinetics and pharmacodynamics were studied.

METHODS

This was an open-label, single-dose, 2 × 2 factorial study. Healthy young (aged 18-40 years) and elderly (aged ≥ 65 years) male and female subjects received a single oral 20 mg dose of apixaban. Blood and urine samples were collected for pharmacokinetic and pharmacodynamic (blood only) analyses. Subjects were monitored for adverse events throughout the study.

RESULTS

Seventy-nine subjects were enrolled into four groups: young males (n = 20), elderly males (n = 20), young females (n = 20) and elderly females (n = 19). Age did not affect the maximum observed plasma concentration (C max). The mean area under the concentration-time curve from time zero extrapolated to infinite time (AUC∞) was 32% greater in elderly subjects than in young subjects. The mean C max and AUC∞ values were 18 and 15% higher, respectively, in females than in males. The time course of the mean international normalized ratio (INR), modified prothrombin time (mPT) and anti-Xa activity tracked the apixaban concentration-time curve. All three pharmacodynamic measures exhibited a positive linear correlation with the plasma apixaban concentration. Differences in the mean INR, mPT and anti-Xa activity between age and sex groups were small (<15% at the maximum mean values) and were generally related to pharmacokinetic differences. However, anti-Xa activity demonstrated less variability than the INR or mPT, and may have utility as a bioassay for apixaban. Apixaban was well tolerated, with no serious adverse events.

CONCLUSION

There were no clinically meaningful age- or sex-related differences in the pharmacokinetics and pharmacodynamics of apixaban that would require dose modification on the basis of age or sex alone.

Effect of ketoconazole and diltiazem on the pharmacokinetics of apixaban, an oral direct factor Xa inhibitor

AIM

Apixaban is an orally active inhibitor of coagulation factor Xa and is eliminated by multiple pathways, including renal and non-renal elimination. Non-renal elimination pathways consist of metabolism by cytochrome P450 (CYP) enzymes, primarily CYP3A4, as well as direct intestinal excretion. Two single sequence studies evaluated the effect of ketoconazole (a strong dual inhibitor of CYP3A4 and P-glycoprotein [P-gp]) and diltiazem (a moderate CYP3A4 inhibitor and a P-gp inhibitor) on apixaban pharmacokinetics in healthy subjects.

METHOD

In the ketoconazole study, 18 subjects received apixaban 10 mg on days 1 and 7, and ketoconazole 400 mg once daily on days 4-9. In the diltiazem study, 18 subjects received apixaban 10 mg on days 1 and 11 and diltiazem 360 mg once daily on days 4-13.

RESULTS

Apixaban maximum plasma concentration and area under the plasma concentration-time curve extrapolated to infinity increased by 62% (90% confidence interval [CI], 47, 78%) and 99% (90% CI, 81, 118%), respectively, with co-administration of ketoconazole, and by 31% (90% CI, 16, 49%) and 40% (90% CI, 23, 59%), respectively, with diltiazem.

CONCLUSION

A 2-fold and 1.4-fold increase in apixaban exposure was observed with co-administration of ketoconazole and diltiazem, respectively.

The Prevention of Venous Thromboembolism in Surgical Patients

Patients undergoing surgery are at an increased risk of VTE. Since the early 1990s the prevention of VTE has been dominated by the administration of low-molecular weight heparin during admission. New oral anticoagulants have been extensively researched and have increased in popularity. This chapter reviews why surgical patients are at increased risk of VTE and summaries both the pharmacological and mechanical methods of prophylaxis available.

Reducing the risk of venous thromboembolism using apixaban - patient perspectives and considerations. Should more attention be given to females?

BACKGROUND

New oral anticoagulant agents, such as apixaban, rivaroxaban, dabigatran, or endoxaban, have recently become for patients an alternative option to conventional treatment in the therapy of venous thromboembolism (VTE). Thus, we aimed to review the available information on adverse events (AEs) of apixaban compared to conventional therapy (heparin or vitamin K antagonists) in randomized controlled trials (RCTs) on patients treated for VTE, with a particular attention to sex subgroups.

METHODS

An electronic search in MEDLINE and Embase was performed by using the keywords "apixaban" and "venous thromboembolism". All RCTs focused on apixaban in the treatment and prevention of VTE were evaluated for the presence of AEs. AEs were classified as serious, bleeding, and cause of discontinuation. Moreover, we also searched by using the keywords "gender" and "venous thromboembolism" and "anticoagulants".

RESULTS

Considering all subjects enrolled in the eleven RCTs as a whole to investigate the occurrence of AEs, we extrapolated an events/subjects rate of 57.8% for AEs (6,445/11,144), 7.7% for serious AEs (975/12,647), 9.1% for bleeding events (1,229/13,454), and 3.2% for discontinuation of apixaban (421/13,039). The percentage of AEs was lower in subjects treated with apixaban than in those treated with conventional VTE therapy (53% vs 56.3%, respectively). However, only one study provided data on separate analysis by sex of either efficacy or safety of apixaban.

CONCLUSION

Under the patient's perspective, apixaban could represent a good choice in the treatment of VTE, due to its pharmacological, economical, and safety profile. These positive aspects are certainly present in both sexes, since the available studies include a correct percentage of women, but data with separate analyses by sex are extremely limited. Future clinical trials should include in their results on clinical impact and outcomes a stratification by sex, and studies aimed to evaluate possible sex-related differences for these drugs should be strongly encouraged.

Effects of a Foot Pump on the Incidence of Deep Vein Thrombosis After Total Knee Arthroplasty in Patients Given Edoxaban: A Randomized Controlled Study

We conducted a randomized clinical trial to compare the effectiveness of the A-V Impulse System foot pump for reducing the incidence of deep-vein thrombosis (DVT) after total knee arthroplasty (TKA) in patients under edoxaban thromboprophylaxis. Patients undergoing primary TKA at our institution between September 2013 and March 2015 were enrolled after obtaining informed consent. The patients were randomized to use the foot pump (n = 58) and not to use the foot pump (n = 62). Both groups were given prophylactic edoxaban. Primary outcomes were any DVT as detected by bilateral ultrasonography up to postoperative day 10 (POD10) and pulmonary embolism (PE) up to POD28. The safety outcomes were bleeding and death of any cause up to POD28. Plasma D-dimer levels were measured before TKA and on POD10 after TKA. Immunoglobulin G (IgG)-class anti-PF4/heparin antibodies were measured using an IgG-specific enzyme-linked immunosorbent assay. The incidences of any DVT up to POD28 were 31.0% and 17.7% in patients with or without the foot pump, respectively. The incidences of major bleeding up to POD28 were 5.1% and 4.8% in patients with or without the foot pump, respectively. Foot pump use did not significantly reduce the incidence of DVTs in patients undergoing TKA under edoxaban thromboprophylaxis. Although seroconversion of anti-PF4/heparin antibodies was confirmed in one-fourth of patients, the seroconversion rates did not differ between patients with (20.7%) or without (25.8%) foot pump use. This study shows that the A-V Impulse system foot pump did not affect the incidence of DVT under edoxaban thromboprophylaxis in patients undergoing TKA. Seroconversion of anti-PF4/heparin antibodies was detected in a significant number of patients who underwent TKA under antithrombotic prophylaxis using edoxaban.

The evolution of anticoagulant therapy

Arterial and venous thromboembolism are leading causes of morbidity and mortality around the world. For almost 70 years, heparins (unfractionated heparin and low molecular weight heparins) and vitamin K antagonists have been the leading therapeutic medical options for the treatment and prevention of thromboembolic disorders. Nevertheless, the many limitations of these traditional anticoagulants have fuelled the search for novel agents over the past 15 years, and a new class of oral anticoagulants that specifically target activated factor X and thrombin has been developed and is now commercially available. In this narrative review, the evolution of anticoagulant therapy is summarised, with a focus on newer oral anticoagulants.

Systematic review with meta-analysis: the risk of major gastrointestinal bleeding with non-vitamin K antagonist oral anticoagulants

BACKGROUND

Gastrointestinal (GI) bleeding is a common complication among anticoagulated patients. Non-vitamin K antagonist oral anticoagulants (NOACs) are associated with increased risk of GI (major and clinically relevant non-major) bleeding. However, more information is needed regarding severe events.

AIM

To evaluate the risk of NOACs major GI bleeding.

METHODS

We searched for phase III randomised clinical trials (RCT) evaluating NOACs (apixaban, dabigatran, edoxaban and rivaroxaban) and reporting major GI bleeding events, in MEDLINE, Cochrane Library, SciELO collection and Web of Science databases (July 2015). Meta-analysis was performed to estimate risk ratio (RR) and 95% confidence intervals (95% CIs). Heterogeneity was assessed with the I(2) test.

RESULTS

A total of 23 studies were included. Among patients with atrial fibrillation, the risk of major GI bleeding was not different between NOACs and vitamin K antagonists (VKA) (RR 1.08, 95% CI 0.85-1.36, I(2)  = 78%; 5 RCTs) or acetylsalicylic acid (RR 0.78, 95% CI 0.36-1.72; 1 RCT). Similar results were found for patients undergoing orthopaedic surgery and those with venous thromboembolism. NOACs were not found to increase the risk compared to low-molecular-weight heparin (LWMH) alone (RR 1.42, 95% CI 0.55-3.71, I(2)  = 7%; 8 RCTs), the sequential treatment with LMWH-VKA (RR 0.77, 95% CI 0.49-1.21, I(2)  = 43%; 7 RCTs) or placebo (RR 1.48, 95% CI 0.15-14.84, I(2)  = 21%; 2 RCTs).

CONCLUSION

Despite previous evidence supporting the association of non-vitamin K antagonist oral anticoagulants and overall GI bleeding, non-vitamin K antagonist oral anticoagulants are not associated with increased risk of major GI bleeding compared to other anticoagulant drugs (with known increased risk of these events).

Oral direct factor Xa inhibitor versus enoxaparin for thromboprophylaxis after hip or knee arthroplasty: Systemic review, traditional meta-analysis, dose-response meta-analysis and network meta-analysis

OBJECTIVES

To analyze the efficacy and safety of direct factor Xa inhibitors for thromboprophylaxis after total hip or knee replacement. To delineate the dose response effect of direct factor Xa inhibitors. To compare the efficacy between any two direct factor Xa inhibitors.

DESIGN

Systemic review, traditional meta-analysis, dose-response meta-analysis and network meta-analysis.

DATA SOURCE

PubMed, EMBASE and Cochrane Library.

STUDY SELECTION

Randomized controlled trials of rivaroxaban, apixaban, betrixaban, darexaban and edoxaban were compared with enoxaparin for thromboprophylaxis after total hip or knee replacement. Two reviewers independently checked the quality of RCTs. Another two investigators independently extracted data. The primary efficacy outcomes (composite of deep venous thrombosis, non-fatal pulmonary embolism and death of all causes) and the primary bleeding outcomes (major bleeding and non-major but clinically relevant bleeding) were summarized for meta-analysis. Stata software was used for traditional meta-analysis and dose-response meta-analysis, and Winbugs software was used for network meta-analysis.

RESULTS

Twenty trials with 38,507 subjects in the intention-to-treat population were included. Compared with enoxaparin, the risk of total venous thromboembolism was lower with rivaroxaban (relative risk 0.70, 95% confidence interval 0.60 to 0.81), apixaban (0.62, 0.47 to 0.81), and edoxaban (0.62, 0.39 to 0.97) and similar to darexaban (0.96, 0.84 to 1.11) and betrixaban (1.28, 0.97 to 1.68). Compared with enoxaparin, the risk of major or clinically relevant non-major bleeding was higher with rivaroxaban (1.52, 1.14 to 2.02), lower with betrixaban (0.34, 0.14 to 0.84) and similar to apixaban (0.88, 0.73 to 1.05), darexaban (0.85, 0.66 to 1.09) or edoxaban (1.30, 0.72 to 2.33). The risk of major and clinically relevant non-major bleeding of rivaroxaban had a linear relationship with its treatment doses; the risk of total venous thromboembolism of betrixaban and darexaban had linear relationships with their respective treatment doses. There was no linear nor non-liner relationships between the effect of apixaban and its treatment dose. The ranking of total venous thromboembolism risk from low to high was: rivaroxaban, apixaban, edoxaban, enoxaparin, darexaban, and betrixaban. The ranking of major and clinically relevant non-major bleeding from low to high was: betrixaban, enoxaparin, darexaban, edoxaban, apixaban, and rivaroxaban.

CONCLUSIONS

Direct oral factor Xa inhibitors are more effective to prevent venous thromboembolism after total hip or knee replacement. Their anticoagulant effect was not necessarily compromised with a higher bleeding risk. Rivaroxaban, apixaban and edoxaban showed a better anticoagulant effect, as compared with enoxaparin. Rivaroxaban had a higher bleeding rate, while apixaban and edoxaban did not show significantly higher bleeding risks.

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.

Thromboprophylaxis with apixaban and the risk of pulmonary embolism in patients undergoing knee replacement surgery

Background

Apixaban, a novel oral anticoagulant, is also used for deep vein thrombosis (DVT) prophylaxis. In this study, we sought to critically evaluate the differences in the rates of symptomatic DVT and bleeding, and analyze the rates of pulmonary embolism (PE) in subgroups of patients from ADVANCE I and II trials given their similar indication and design.

Methods

Studies were identified through electronic literature searches of MEDLINE, clinicaltrial.gov, SCOPUS, and EMBASE up to January 2014. Phase III RCTs involving use of apixaban and enoxaparin for thromboprophylaxis in patients undergoing total knee or hip replacement were included. Study-specific odds ratios were calculated and between-study heterogeneity was assessed using the I² statistics.

Results

In three studies involving 11,659 patients, the risk of symptomatic DVT (pooled OR 0.38, 95% CI 0.16–0.90, I²=0%, p=0.03) and bleeding (pooled OR 0.87, 95% CI 0.77–0.99, I²=0%, p=0.03) was less in apixaban group compared to the enoxaparin group. However, it was interesting to note that on subgroup analysis, the risk of PE was higher with apixaban when used for thromboprophylaxis in knee replacement surgery (pooled OR 2.58, 95% CI 1.10–6.04, I²=0%, p=0.03).

Conclusion

Apixaban was found to be associated with lower risk of symptomatic DVT and bleeding compared to enoxaparin when used for thromboprophylaxis in patients undergoing knee and hip replacement surgeries. However, it was associated with higher risk of PE in patients undergoing knee replacement.

Administration of 4-Factor Prothrombin Complex Concentrate as an Antidote for Intracranial Bleeding in Patients Taking Direct Factor Xa Inhibitors

OBJECTIVE

Direct factor Xa inhibitors rivaroxaban and apixaban are efficacious alternatives to warfarin and confer a lower risk of spontaneous intracranial hemorrhage (ICH); however, they lack a validated reversal strategy. We evaluated the efficacy and safety of 4-factor prothrombin complex concentrate (PCC) administration on rivaroxaban- and apixaban-mediated coagulopathy in patients with traumatic and spontaneous ICH.

METHODS

Retrospective review of patients presenting with traumatic and spontaneous ICH and concurrent use of rivaroxaban or apixaban. Demographic factors, reason for anticoagulation, hemorrhage type and location, Glasgow coma scale score, and when appropriate, ICH score, were included. Patient charts were reviewed for in-hospital mortality, thromboembolic events, pulmonary complications, worsening of hemorrhage, hemorrhagic complications after neurosurgical intervention, and 90-day modified Rankin scale score.

RESULTS

Eighteen patients met inclusion criteria; 16 used rivaroxaban and 2 used apixaban. Eight patients presented with traumatic ICH, 8 with hemorrhagic stroke, 1 with subarachnoid hemorrhage, and 1 patient with tumoral hemorrhage. Mean Glasgow coma scale score was 12.6 (range, 6-15) and mean ICH score was 2.3 (range, 0-4). After reversal with PCC, 1 patient (5.6%) demonstrated worsening of ICH on follow-up head computed tomography. PCCs were administered before emergent placement of an external ventricular drain in 1 individual, with no hemorrhagic complications. Six patients (33.3%) experienced in-hospital mortality: family withdrew care in 4 and 2 died due to pneumonia. There was 1 (5.6%) thromboembolic complication. Favorable outcomes at 90 days were seen in 6 patients (33.3%).

CONCLUSIONS

Despite no studies demonstrating the efficacy of 4-factor PCC administration for reversal of coagulopathy in patients on direct factor Xa inhibitors, our early experience demonstrates it to be safe, yet potentially reducing hemorrhagic complications and hematoma expansion in this critically ill population.

Direct oral anticoagulants: new drugs and new concepts

Direct oral anticoagulants (DOACs) are approved for multiple thromboembolic disorders and provide advantages over existing agents. As with all anticoagulants, management protocols for the eventuality of bleeding are important. Randomized phase III studies generally show that DOACs have a similar risk of clinically relevant bleeding compared with standard anticoagulants, with reductions in major bleeding in some cases. This may be particularly important in patients with atrial fibrillation, for whom the rate of intracranial hemorrhage was approximately halved with DOACs compared with warfarin. Conversely, the risk of gastrointestinal bleeding may be increased. Specific patient characteristics, such as renal impairment, comedications, and particular aspects of each drug, including the proportion eliminated by the kidneys, must be taken into account when assessing the risk of bleeding. Although routine coagulation monitoring of DOACs is not required, it may be useful under some circumstances. Of the traditional clotting assays, a sensitive and calibrated prothrombin time may be useful for detecting the presence or absence of clinically relevant factor Xa inhibitor concentrations (rivaroxaban or apixaban), but specific anti-factor Xa assays can measure drug levels quantitatively. For dabigatran, the results of an activated partial thromboplastin time test may exclude a clinically relevant pharmacodynamic effect, but a calibrated dilute thrombin time assay can be used for quantification of drug levels. In the event of mild or moderate bleeding, normal hemostatic support measures are recommended. For life-threatening bleeding, use of nonspecific prohemostatic agents may be considered, although clinical evidence is scarce. Specific antidotes are in development.

Apixaban for the prophylaxis and treatment of deep vein thrombosis and pulmonary embolism: an evidence-based review

Venous thromboembolism (VTE) results in significant morbidity and mortality. The prevention and treatment of VTE is managed with anticoagulant therapy, historically parenteral anticoagulants such as unfractionated heparin, low molecular weight heparin, and fondaparinux, and oral vitamin K antagonists such as warfarin. In the last few years, several target-specific oral anticoagulants have been developed, including the direct thrombin inhibitor dabigatran and anti-Xa inhibitors rivaroxaban, apixaban, and edoxaban. The target-specific oral anticoagulants have proven to be noninferior to vitamin K antagonists and heparins in the prevention and treatment of VTE. This review will focus on the pharmacology, clinical trial data, and laboratory assessment of apixaban. Moreover, perioperative management, use in special populations, and management of bleeding complications in patients taking apixaban for the prevention and treatment of VTE will also be discussed.

Evaluation of the effect of naproxen on the pharmacokinetics and pharmacodynamics of apixaban

AIM

To assess pharmacokinetic and pharmacodynamic interactions between naproxen (a non-steroidal anti-inflammatory drug) and apixaban (an oral, selective, direct factor-Xa inhibitor).

METHOD

In this randomized, three period, two sequence study, 21 healthy subjects received a single oral dose of apixaban 10 mg, naproxen 500 mg or co-administration of both. Blood samples were collected for determination of apixaban and naproxen pharmacokinetics and pharmacodynamics (anti-Xa activity, international normalized ratio [INR] and arachidonic acid-induced platelet aggregation [AAI-PA]). Adverse events, bleeding time and routine safety assessments were also evaluated.

RESULTS

Apixaban had no effect on naproxen pharmacokinetics. However, following co-administration, apixaban AUC(0,∞), AUC(0,t) and Cmax were 54% (geometric mean ratio 1.537; 90% confidence interval (CI) 1.394, 1.694), 55% (1.549; 90% CI 1.400, 1.713) and 61% (1.611; 90% CI 1.417, 1.831) higher, respectively. Mean (standard deviation [SD]) anti-Xa activity at 3 h post-dose was approximately 60% higher following co-administration compared with apixaban alone, 4.4 [1.0] vs. 2.7 [0.7] IU ml(-1) , consistent with the apixaban concentration increase following co-administration. INR was within the normal reference range after all treatments. AAI-PA was reduced by approximately 80% with naproxen. Co-administration had no impact beyond that of naproxen. Mean [SD] bleeding time was higher following co-administration (9.1 [4.1] min) compared with either agent alone (5.8 [2.3] and 6.9 [2.6] min for apixaban and naproxen, respectively).

CONCLUSION

Co-administration of naproxen with apixaban results in higher apixaban exposure and appears to occur through increased apixaban bioavailability. The effects on anti-Xa activity, INR and inhibition of AAI-PA observed in this study were consistent with the individual pharmacologic effects of apixaban and naproxen.

Comparative coronary risks of apixaban, rivaroxaban and dabigatran: a meta-analysis and adjusted indirect comparison

AIMS

There are concerns regarding increased risk of acute coronary syndrome with dabigatran. We aimed to assess whether alternative treatment options such as rivaroxaban or apixaban carry a similar risk as compared with dabigatran.

METHODS

We searched MEDLINE and EMBASE for randomized controlled trials of apixaban, dabigatran or rivaroxaban against control (placebo, heparin or vitamin K antagonist). We pooled odds ratios (OR) for adverse coronary events (acute coronary syndrome or myocardial infarction) using fixed effect meta-analysis and assessed heterogeneity with I(2) . We conducted adjusted indirect comparisons to compare risk of adverse coronary events with apixaban or rivaroxaban vs. dabigatran.

RESULTS

Twenty-seven randomized controlled trials met the inclusion criteria. Dabigatran was associated with a significantly increased risk of adverse coronary events in pooled analysis of nine trials (OR 1.45, 95% CI 1.14, 1.86). There was no signal for coronary risk with apixaban from nine trials (pooled OR 0.89, 95% CI 0.78, 1.03) or rivaroxaban from nine trials (pooled OR 0.81, 95% CI 0.72, 0.93). Overall, adjusted indirect comparison suggested that both apixaban (OR 0.61, 95% CI 0.44, 0.85) and rivaroxaban (OR 0.54; 95% CI 0.39, 0.76) were associated with lower coronary risk than dabigatran. Restricting the indirect comparison to a vitamin K antagonist as a common control, yielded similar findings, OR 0.57 (95% CI 0.39, 0.85) for apixaban vs. dabigatran and 0.53 (95% CI 0.37, 0.77) for rivaroxaban vs. dabigatran.

CONCLUSIONS

There are significant differences in the comparative safety of apixaban, rivaroxaban and dabigatran with regards to acute coronary adverse events.

Lack of consistency in the relationship between asymptomatic DVT detected by venography and symptomatic VTE in thromboprophylaxis trials

Asymptomatic deep-vein thrombosis (DVT) detected by mandatory venography, a surrogate outcome, comprises most of the efficacy outcome events in recent thromboprophylaxis trials. The validity of this surrogate to estimate trade-off between thrombotic and bleeding events in these clinical trials requires a consistent relationship between asymptomatic DVT and symptomatic venous thromboembolism (VTE). In this systematic review of high quality VTE prevention trials, we examined the consistency of the ratios of asymptomatic DVT to symptomatic VTE across a broad range of indications. Studies were identified from citations listed in the chapters on VTE prevention in the antithrombotic guidelines by the American College of Chest Physicians, 2012. A study was eligible if it: 1) was a randomised trial comparing an anticoagulant with standard of care; 2) included at least 500 participants; 3) reported asymptomatic or all DVT rates; and 4) reported symptomatic VTE rates. Of the 26 eligible trials, 19 trials were conducted in orthopaedic patients, five in general surgery patients and two in general medical patients. The overall median rates (ranges) for asymptomatic DVT and symptomatic VTE were 9.11 % (0.75 to 54.87 %) and 0.49 % (0.00 to 3.10 %), respectively. The median ratio was 14.53, with a wide range (2.75 to 103.86). Wide variability in the ratios persisted despite indication- and anticoagulant-specific analyses. In VTE prevention trials of alternative anticoagulants, the wide variability in the ratios of asymptomatic DVT to symptomatic VTE precludes judging the trade-off between thrombotic and bleeding events on the basis of composite outcomes dominated by venographic DVT.

Dosing of Target-Specific Oral Anticoagulants in Special Populations

OBJECTIVE

To review current literature for target-specific oral anticoagulants (TSOACs) and provide critical analysis for dosing recommendations in special population groups.

DATA SOURCES

A literature search was conducted in Medline (1996 to April week 2 2015) and Embase (1980 to 2015 week 16) using key terms dabigatran, rivaroxaban, apixaban, edoxaban, kidney diseases, liver diseases, elderly, obesity, and special populations.

STUDY SELECTION AND DATA EXTRACTION

Randomized controlled trials in English assessing efficacy and safety of TSOACs in healthy adults and special populations were selected for analysis.

DATA SYNTHESIS

Phase 3 trials for TSOACs predominately excluded patients with severe renal impairment or active liver disease. There were no exclusion criteria based on age, body weight or body mass index. Additional conclusions were made in special populations, including those with renal or liver impairment and obese and elderly patients, based on secondary analyses, pharmacokinetic, and pharmacodynamic studies.

CONCLUSIONS

Pharmacokinetic and pharmacodynamic changes associated special populations may alter clinical decision with regard to drug selection and dosing. It is valuable to understand the rationale for labeled dosing recommendations in nonvalvular atrial fibrillation and venous thromboembolism treatment and prevention, particularly in patients that fall into special population groups. Furthermore, the use of TSOACs is likely to increase as clinicians gain experience with these agents and additional TSOACs and indications are approved.

Edoxaban: an update on the new oral direct factor Xa inhibitor

Edoxaban is a once-daily oral anticoagulant that rapidly and selectively inhibits factor Xa in a concentration-dependent manner. This review describes the extensive clinical development program of edoxaban, including phase III studies in patients with non-valvular atrial fibrillation (NVAF) and symptomatic venous thromboembolism (VTE). The ENGAGE AF-TIMI 48 study (N = 21,105; mean CHADS₂ score 2.8) compared edoxaban 60 mg once daily (high-dose regimen) and edoxaban 30 mg once daily (low-dose regimen) with dose-adjusted warfarin [international normalized ratio (INR) 2.0–3.0] and found that both regimens were non-inferior to warfarin in the prevention of stroke and systemic embolism in patients with NVAF. Both edoxaban regimens also provided significant reductions in the risk of hemorrhagic stroke, cardiovascular mortality, major bleeding and intracranial bleeding. The Hokusai-VTE study (N = 8,292) in patients with symptomatic VTE had a flexible treatment duration of 3–12 months and found that following initial heparin, edoxaban 60 mg once daily was non-inferior to dose-adjusted warfarin (INR 2.0–3.0) for the prevention of recurrent VTE, and also had a significantly lower risk of bleeding events. Both studies randomized patients at moderate-to-high risk of thromboembolic events and were further designed to simulate routine clinical practice as much as possible, with edoxaban dose reduction (halving dose) at randomisation or during the study if required, a frequently monitored and well-controlled warfarin group, a well-monitored transition period at study end and a flexible treatment duration in Hokusai-VTE. Given the phase III results obtained, once-daily edoxaban may soon be a key addition to the range of antithrombotic treatment options.

Unmet Needs in Anticoagulant Therapy: Potential Role of Rivaroxaban

The new generation of non-vitamin K antagonist oral anticoagulants (NOACs) have been welcomed as a convenient alternative to warfarin. Three new oral anticoagulants, dabigatran etexilate, rivaroxaban and apixaban have been approved for the prevention of stroke and systemic embolism (SSE) in patients with atrial fibrillation (AF) and the prevention of venous thromboembolic events (VTEs) in patients who have undergone elective hip or knee replacement surgery. Dabigatran etexilate and rivaroxaban are also indicated for the treatment of VTE and the long-term prevention of recurrent deep vein thrombosis (DVT) and pulmonary embolism (PE). A fourth agent, edoxaban, has been successfully tested for several indications but is not yet approved for use in North America or Europe. Building on these successes, new trials are planned to address remaining unmet needs and knowledge gaps. This paper examines the unresolved issues in anticoagulant therapy with a focus on planned and ongoing trials.

Post-operative arterial thrombosis with non-vitamin K antagonist oral anticoagulants after total hip or knee arthroplasty

The incidence of post-operative arterial thrombosis (AT) (acute myocardial infarction [AMI] and ischaemic stroke) is increased in patients undergoing total hip replacement (THR) or total knee replacement (TKR). We compared the incidence of post-operative AT in non-vitamin K antagonist oral anticoagulants (NOACs)-treated and enoxaparin-treated patients, performing a systematic review of phase III randomised controlled trials (RCTs) of venous thromboembolism (VTE) prophylaxis in THR and TKR. Studies were identified by electronic search of MEDLINE and EMBASE database until July 2014. Differences between NOACs and enoxaparin groups in the efficacy and safety outcomes were expressed as odds ratios (ORs) with pertinent 95 % confidence intervals (95 % CI). Statistical heterogeneity was assessed with the I² statistic. Eleven phase III RCTs for a total of 31,319 patients were included. Patients underwent TKR in six studies and THR in five studies. The NOACs under study were dabigatran (four studies), apixaban (three studies) and rivaroxaban (four studies). AT occurred in 0.23 % of patients on NOACs and in 0.27 % of patients on enoxaparin: the OR at fixed-effect model was 0.86 (95 % CI 0.53-1.40; I² 11 %). No differences in AT incidence among the three NOACs were observed. The incidence of major and clinically relevant bleeding was similar in NOACs and enoxaparin groups (OR 1.03, 95 % CI 0.92-1.15; I² 38 %). In conclusion, in RCTs of pharmacological VTE prophylaxis in patients undergoing THR or TKR, there was no difference in the incidence of post-operative AT among patients treated with NOACs, compared to those treated with enoxaparin.