Dabigatran and rivaroxaban for prevention of venous thromboembolism--systematic review and adjusted indirect comparison

The effectiveness of venous thromboembolism prophylaxis interventions in trauma patients: A systematic review and network meta-analysis

BACKGROUND

Venous thromboembolism (VTE) is a major complication of trauma. Currently, there are few studies summarising the evidence for prophylaxis in trauma settings. This review provides evidence for the use of VTE prophylactic interventions in trauma patients to produce evidence-based guidelines.

METHODS

A PRISMA-compliant review was conducted from Sep 2021 to June 2023, using Embase, Medline and Google Scholar. The inclusion criteria were: randomized-controlled trials (RCTs) in English published after 2000 of adult trauma patients comparing VTE prophylaxis interventions, with a sample size higher than 20. The network analysis was conducted using RStudio. The results of the pairwise comparisons were presented in the form of a league table. The quality of evidence and heterogeneity sensitivity were assessed. The primary outcome focused on venous thromboembolism (VTE), and examined deep vein thrombosis (DVT) and pulmonary embolism (PE) as separate entities. The secondary outcomes included assessments of bleeding and mortality. PROSPERO registration: CRD42021266393.

RESULTS

Of the 7,948 search results, 23 studies with a total of 21,312 participants fulfilled screening criteria, which included orthopaedic, spine, solid organ, brain, spinal cord, and multi-region trauma. Of the eight papers comparing chemical prophylaxis medications in patients with hip or lower limb injuries, fondaparinux and enoxaparin were found to be significantly superior to placebo in respect of prevention of DVT, with no increased risk of bleeding. Regarding mechanical prophylaxis, meta-analysis of two studies of inferior vena cava filters failed to provide significant benefits to major trauma patients.

CONCLUSION

Enoxaparin and fondaparinux are safe and effective options for VTE prevention in trauma patients, with fondaparinux being a cheaper and easier administration option between the two. Inconclusive results were found in mechanical prophylaxis, requiring more larger-scale RCTs.

Venous Thromboembolism Prophylaxis in Major Orthopedic Surgeries and Factor XIa Inhibitors

Venous thromboembolism (VTE), comprising pulmonary embolism (PE) and deep vein thrombosis (DVT), poses a significant risk during and after hospitalization, particularly for surgical patients. Among various patient groups, those undergoing major orthopedic surgeries are considered to have a higher susceptibility to PE and DVT. Major lower-extremity orthopedic procedures carry a higher risk of symptomatic VTE compared to most other surgeries, with an estimated incidence of ~4%. The greatest risk period occurs within the first 7-14 days following surgery. Major bleeding is also more prevalent in these surgeries compared to others, with rates estimated between 2% and 4%. For patients undergoing major lower-extremity orthopedic surgery who have a low bleeding risk, it is recommended to use pharmacological thromboprophylaxis with or without mechanical devices. The choice of the initial agent depends on the specific surgery and patient comorbidities. First-line options include low-molecular-weight heparins (LMWHs), direct oral anticoagulants, and aspirin. Second-line options consist of unfractionated heparin (UFH), fondaparinux, and warfarin. For most patients undergoing knee or hip arthroplasty, the initial agents recommended for the early perioperative period are LMWHs (enoxaparin or dalteparin) or direct oral anticoagulants (rivaroxaban or apixaban). In the case of hip fracture surgery, LMWH is recommended as the preferred agent for the entire duration of prophylaxis. However, emerging factor XI(a) inhibitors, as revealed by a recent meta-analysis, have shown a substantial decrease in the occurrence of VTE and bleeding events among patients undergoing major orthopedic surgery. This discovery poses a challenge to the existing paradigm of anticoagulant therapy in this specific patient population and indicates that factor XI(a) inhibitors hold great promise as a potential strategy to be taken into serious consideration.

Ameliorative Effect of Dabigatran on CFA-Induced Rheumatoid Arthritis via Modulating Kallikrein-Kinin System in Rats

Rheumatoid arthritis is an autoimmune disease that affects joints, leading to swelling, inflammation, and dysfunction in the joints. Recently, research efforts have been focused on finding novel curative approaches for rheumatoid arthritis, as current therapies are associated with adverse effects. Here, we examined the effectiveness of dabigatran, the antithrombotic agent, in treating complete Freund’s adjuvant (CFA)-induced arthritis in rats. Subcutaneous injection of a single 0.3 mL dosage of CFA into the rat’s hind leg planter surface resulted in articular surface deformities, reduced cartilage thickness, loss of intercellular matrix, and inflammatory cell infiltration. There were also increased levels of the Anti-cyclic citrullinated peptide antibody (ACPA), oxidative stress, and tissue Receptor activator of nuclear factor–kappa B ligand (RANKL). Proteins of the kallikrein-kinin system (KKS) were also elevated. The inhibitory effects of dabigatran on thrombin led to a subsequent inhibition of KKS and reduced Toll-like receptor 4 (TLR4) expression. These effects also decreased RANKL levels and showed anti-inflammatory and antioxidant effects. Therefore, dabigatran could be a novel therapeutic strategy for arthritis.

Efficacy and Safety of Enoxaparin versus New Oral Anticoagulants to Prevent Venous Thromboembolism after Total Hip Replacement: A Systematic Review and Meta-Analysis

Prophylactic anticoagulant therapy is recommended for reducing the risk of venous thromboembolism (VTE) after a total hip replacement (THR). However, it is not clear which anticoagulant is preferable. Hence, a systematic review and meta-analysis of randomized double-blind controlled trials (RDBCTs) were conducted to investigate the clinical efficacy and safety of enoxaparin in comparison with newer oral anticoagulants for the prevention of VTE after THR. The Cochrane Library, Scopus, Web of Science, Embase, and PubMed/Medline databases were used for PICO search strategy. Relative risks (RR) of symptomatic VTE, clinically relevant bleeding, mortality, and a net clinical endpoint were estimated employing a random effect meta-analysis. ITC and RevMan software were used for indirect and direct comparisons, respectively. Nine RDBCTs comprising 24,584 patients were included. As compared to enoxaparin, a reduced risk for symptomatic VTE was observed with rivaroxaban (confidence interval [CI]: 0.32–0.77; RR: 0.46%) and comparable with apixaban (0.12–1.26; 0.42%) and dabigatran (0.22–2.20; 0.70%). Contrarily to enoxaparin, a greater risk for clinically relevant bleeding was observed with rivaroxaban (1.03–1.48; 1.23%), comparable with dabigatran (0.96–1.33; 1.10%) and reduced with apixaban (0.19–5.66; 0.96%). In indirect or direct comparisons, the interventions did not differ on the net clinical endpoint. In conclusion, the findings of this meta-analysis revealed no significant difference in the efficacy and safety of new oral anticoagulants as compared to enoxaparin for the prevention of VTE after total hip replacement surgery.

A Review of the Incidence Diagnosis and Treatment of Spontaneous Hemorrhage in Patients Treated with Direct Oral Anticoagulants

Anticoagulation carries a tremendous therapeutic advantage in reducing morbidity and mortality with venous thromboembolism and atrial fibrillation. For over six decades, traditional anticoagulants like low molecular weight heparin and vitamin K antagonists like warfarin have been used to achieve therapeutic anticoagulation. In the past decade, multiple new direct oral anticoagulants have emerged and been approved for clinical use. Since their introduction, direct oral anticoagulants have changed the landscape of anticoagulants. With increasing indications and use in various patients, they have become the mainstay of treatment in venous thromboembolic diseases. The safety profile of direct oral anticoagulants is better or at least similar to warfarin, but several recent reports are focusing on spontaneous hemorrhages with direct oral anticoagulants. This narrative review aims to summarize the incidence of spontaneous hemorrhage in patients treated with direct oral anticoagulants and also offers practical management strategies for clinicians when patients receiving direct oral anticoagulants present with bleeding complications.

Postoperative Thromboprophylaxis With New Oral Anticoagulants is Superior to LMWH in Hip Arthroplasty Surgery: Findings from the Swedish Registry

BACKGROUND

Although the use of thromboprophylaxis is well established, there is no consensus on the preferred thromboprophylaxis regimen after THA; large, population-based studies offer an opportunity to examine this problem in a robust way that can complement results from randomized trials.

QUESTIONS/PURPOSES

Using data from a large national registry, we asked: (1) Is there any difference between low-molecular weight heparin (LMWH) and new oral anticoagulants in preventing symptomatic deep vein thrombosis (DVT) and pulmonary embolism (PE), after THA? (2) Are there any differences in safety parameters, such as bleeding, reoperations and mortality, between LMWH and new oral anticoagulants?

METHODS

Between 2008 and 2012, 78,066 THAs were performed in Sweden. This study evaluated 32,663 (42%) of them, selected through the merger of several national registries. These patients underwent unilateral THA due to primary osteoarthritis. They had not experienced any venous thromboembolic events 5 years before the index operation and were not prescribed potent antithrombotic agents, of any type, in the 6 months before the index operation. Additionally, their postoperative thromboprophylaxis was confirmed in a national registry by purchase of prescribed medications. We divided the cohort into two groups: those patients who received new oral anticoagulants (5752, 18%) and those who received LMWH (26,881, 82%) as postoperative thromboprophylaxis. Our primary endpoints were the frequencies of symptomatic DVT and symptomatic PE within 3 months of surgery. Our secondary comparison was a between-group comparison of bleeding (by way of diagnostic coding), reoperation, and mortality within 3 months of surgery. Odds ratios (OR) are presented with 95% confidence intervals (CIs) as pooled results for the two groups after adjustment for duration of thromboprophylaxis (short or extended for at least 28 days), year of the index operation, Elixhauser comorbidity index, sex, age and previous treatment with platelet aggregation inhibitors.

RESULTS

The risk of symptomatic DVT was lower in the group that received new oral anticoagulants than the group that received LMWH (0.3% versus 0.6%, OR, 0.47; 95% CI, 0.27-0.76; p = 0.026). The risk of symptomatic PE was lower in the group that received new oral anticoagulants than the group that received LMWH (0.1% versus 0.4%, OR, 0.36; 95% CI, 0.16-0.69; p = 0.005). There was no difference in the risk of bleeding (by way of diagnostic coding) (OR, 1.03; 95% CI, 0.82-1.28; p = 0.688), reoperation (OR, 1.02; 95% CI, 0.71-1.44; p = 0.860) or mortality (OR, 0.83; 95% CI, 0.31-1.88; p = 0.883) between groups.

CONCLUSIONS

New oral anticoagulants were associated with a lower risk of symptomatic DVT and symptomatic PE in this large, registry study, and we observed no differences in the risk of bleeding, reoperation, or death between the groups. Although we were able to control for a number of potential confounding variables, we cannot ascertain the indications that drove the prescription decisions in this setting, and there were important between-group differences in terms of duration of thromboprophylaxis (new oral anticoagulants generally were used for a longer period of time after surgery). Future studies, preferably large randomized trials with pragmatic inclusion criteria, to analyze symptomatic DVT, symptomatic PE and death are needed to confirm or refute our findings.

LEVEL OF EVIDENCE

Level III, therapeutic study.

A Prospective Cohort Study of Symptomatic Venous Thromboembolic Events in Foot and Ankle Trauma: The Need for Stratification in Thromboprophylaxis?

The incidence of venous thromboembolic (VTE) events (deep vein thrombophlebitis [DVT] or pulmonary embolism [PE]) in foot and ankle trauma has been low, and the risk/benefit ratio associated with chemoprophylaxis is controversial. We compared the 90-day incidence of VTE events in 3 cohorts: group 1, tendo-Achillis (TA) ruptures managed with full weightbearing in a walker boot; group 2, ankle fractures immobilized non-weightbearing in a below-the-knee cast; and group 3, ankle fractures managed surgically, followed by non-weightbearing in a below-the-knee cast. Data were extracted from 2 prospectively collected trust databases for acute TA ruptures and ankle fractures. VTE risk was assessed using a U.K. national assessment tool. Chemoprophylaxis was prescribed for high-risk patients. The 90-day incidence of symptomatic VTE events was drawn from a trust-wide radiology database. In group 1 (n = 291), the incidence of VTE events was 4.8% (11 [3.8%] DVT, 3 [1.0%] PE) at a mean of 16.1 ± 6.8 days. In group 2 (n = 227), the incidence of VTE events was 2.2% (5 [2.2%] DVT) at a mean of 33.4 ± 11.3 days. In group 3 (n = 199), the incidence of VTE events was 3.0% (5 [2.5%] DVT, 1 [0.5%] PE) at a mean of 37.2 ± 14.2 days. Patients with symptomatic VTE events presented significantly earlier after acute TA rupture compared with after ankle fracture (p = .002). We found the overall incidence of VTE events in foot and ankle trauma was low, with a relatively greater incidence of symptomatic VTE events, which occurred earlier, in acute TA ruptures compared with ankle fractures.

Klinische Studien zu neuen direkten oralen Antikoagulanzien

Um die Wirksamkeit und Verträglichkeit neuer direkter oraler Antikoagulanzien (DOAK) zu vergleichen, müssten idealerweise eine direkte Gegenüberstellung der Substanzen in klinischen Studien durchgeführt werden. Auf Grund des logistischen und finanziellen Aufwandes wird dies aber in absehbarer Zeit nicht geschehen. Indirekte Vergleiche, auch Netzwerkanalysen (NMA) genannt, lassen sich mit den vorliegenden Studien zwischen den DOAKs vornehmen. In der postoperativen Phase nach Knie- und Hüftgelenkersatz und bei Patienten mit Vorhofflimmern sind derzeit diese Vergleich möglich. Indirekte Vergleiche sind jedoch auch mit Einschränkungen behaftet.

Diese Arbeit gibt eine Übersicht der aktuell vorliegenden NMAs und versucht, deren Ergebnisse mit der Pharmakologie der DOAKs und den methodischen Problemen von NMAs zu beleuchten.

Interpretation of endpoints in a network meta-analysis of new oral anticoagulants following total hip or total knee replacement surgery

New oral anticoagulant (NOAC) regimens [dabigatran 150 mg (D150) and 220 mg (D220), rivaroxaban 10 mg (R20), and apixaban 2.5 mg bid (A5)] were effective and safe compared to enoxaparin for the prevention of venous thromboembolism (VTE) following elective total knee (TKR) or hip replacement (THR) surgery. First a cluster analysis was used to identify homogeneous studies for the trial programs of each NOAC. Second, only studies reporting VTE and VTE-related death, major bleeding, and mortality were included. The odds ratio (OR) and 95% confidence interval (CI) were calculated for each NOAC regimen versus the comparator. Third, these data were used for the indirect comparison between NOACs. Cluster analysis identified duration of treatment (10 ± 5 and 34 ± 5 days) as the only homogeneous parameter across all NOAC programs (p>0.05) except for A5 and VTE over 10 ± 5 days (analysis not performed). The results of the calculated OR and 95% CI of the four NOAC regimens over 10 ± 5 and 34 ± 5 days showed inferiority of D150 and D220 compared to R10 for VTE (p<0.01, p<0.001). Comparisons of major bleeding and mortality were not different for all indirect comparisons. Despite the lack of standard definitions for VTE and bleeding outcomes, cluster analysis seems to be an appropriate tool to identify homogeneity across trial programs and to perform an indirect comparison for NOACs for prevention of VTE following TKR and THR surgery.

Assessment of clinically relevant bleeding as a surrogate outcome for major bleeding: validation by meta-analysis of randomized controlled trials

Essentials Surrogacy of clinically relevant bleeding (CRB) for major bleeding has never been validated. Our meta-analysis evaluated CRB surrogacy in trials of new versus traditional anticoagulants. Surrogacy was not validated in orthopedic surgery, venous thromboembolism or atrial fibrillation The difficulty in demonstrating the surrogacy may reflect a lack of homogeneity in its definition SUMMARY: Background Clinically relevant bleeding (CRB), comprising major bleeding and clinically relevant non-major bleeding, has been used as a surrogate for major bleeding in most anticoagulant trials. The validity of this surrogate to estimate trade-off between thrombotic and bleeding events in clinical trials was never assessed. Methods We systematically reviewed randomized phase III trials comparing new anticoagulants with the standard of care for venous thromboembolism prevention following major orthopedic surgery, venous thromboembolism (VTE) treatment, or stroke and systemic embolism prevention in atrial fibrillation (AF), and reporting both major bleeding and CRB rates. The validity of CRB as a surrogate for major bleeding was assessed according to the strength of the association between the relative risks of major bleeding and CRB, measured by the use of R2trial and its 95% confidence interval (CI). Results In the postoperative prophylactic setting (13 studies), major bleeding and CRB rates were 1.12% and 3.56%, respectively, and R2trial was 0.69 (95% CI 0.34-0.93). For acute VTE studies (n = 12), major bleeding and CRB rates were 1.87% and 9.07%; the corresponding R2trial values were 0.28 (95% CI 0.01-0.80) and 0.68 (95% CI 0.09-1.00) when only double-blind studies were considered (n = 7). For AF studies (n = 7; 22 strata), major bleeding and CRB rates were 4.82% and 15.3%, and R2trial was 0.59 (95% CI 0.15-0.82). Conclusion Despite an apparent correlation between CRB and major bleeding in major orthopedic surgery, AF, and double-blind acute VTE studies, the wide CIs suggest that CRB might not be an acceptable surrogate outcome in any of these settings.

Direct Oral Anticoagulants Vs. Enoxaparin for Prevention of Venous Thromboembolism Following Orthopedic Surgery: A Dose-Response Meta-analysis

We carried out a dose–response model‐based meta‐analysis to assess venous thromboembolism (VTE) and bleeding with factor Xa (FXa) inhibitors (apixaban, edoxaban, rivaroxaban) and a thrombin inhibitor (dabigatran) compared with European (EU) (40 mg q.d.) and North American (NA) (30 mg Q12H) dose regimens of a low molecular weight heparin (enoxaparin) following orthopedic surgery. Statistically significant differences in both VTE and bleeding outcomes were found between the NA and EU doses of enoxaparin, with odds ratios (95% confidence interval) for the NA vs. EU dose of 0.73 (0.71–0.76) and 1.20 (1.14–1.29) for total VTE and major bleeding, respectively. At approved doses, estimated odds ratios vs. both doses of enoxaparin for the three FXa inhibitors (range: 0.35–0.75 for VTE; 0.76–1.09 for bleeding) compared with those for dabigatran (range: 0.66–1.21 for VTE; 1.10–1.38 for bleeding) suggested generally greater efficacy and less bleeding for the FXa inhibitors.

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.

Opportunities for improvement: anticoagulation in patients undergoing total knee or hip replacement

BACKGROUND

According to guidelines, initiation of pharmacological thromboprophylaxis after total knee or hip replacement is recommended and associated with improved patient outcomes. However, data on how these recommendations are followed in clinical practice are sparse.

METHODS

All patients undergoing first-time total knee or hip replacement in Denmark 2008-2011 were identified. By cross-referencing Danish nationwide registries, quantitative use of anticoagulants administered orally and subcutaneously post-discharge was assessed by number of claimed prescriptions after surgery. Logistic regression analysis was used to identify factors associated with initiation of prophylaxis.

RESULTS

A total of 50,389 patients were included in the study (median age 69, inter-quartile range 62-76). Novel oral anticoagulants were initiated in 14.7 % of the patients and heparins/fondaparinux in 2.3 % of the patients. The use of anticoagulants increased from 6.3 % in 2008 to 30.0 % of patients in 2011. Among patients initiating prophylaxis with a novel oral anticoagulant post-discharge, almost all were treated according to guidelines in terms of treatment duration. Factors significantly associated with an increased chance of prophylaxis among total hip replacement patients were: age (per 10-year increments) and female gender.

CONCLUSIONS

Use of pharmacological thromboprophylaxis after total knee or hip replacement was low, but increasing during the study period. This is probably due to increased availability of novel oral anticoagulants. Further initiatives to increase guideline recommended use of prophylactic anticoagulation after orthopaedic surgery are warranted.

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.

Recent meta-analyses neglect previous systematic reviews and meta-analyses about the same topic: a systematic examination

BACKGROUND

As the number of systematic reviews is growing rapidly, we systematically investigate whether meta-analyses published in leading medical journals present an outline of available evidence by referring to previous meta-analyses and systematic reviews.

METHODS

We searched PubMed for recent meta-analyses of pharmacological treatments published in high impact factor journals. Previous systematic reviews and meta-analyses were identified with electronic searches of keywords and by searching reference sections. We analyzed the number of meta-analyses and systematic reviews that were cited, described and discussed in each recent meta-analysis. Moreover, we investigated publication characteristics that potentially influence the referencing practices.

RESULTS

We identified 52 recent meta-analyses and 242 previous meta-analyses on the same topics. Of these, 66% of identified previous meta-analyses were cited, 36% described, and only 20% discussed by recent meta-analyses. The probability of citing a previous meta-analysis was positively associated with its publication in a journal with a higher impact factor (odds ratio, 1.49; 95% confidence interval, 1.06 to 2.10) and more recent publication year (odds ratio, 1.19; 95% confidence interval 1.03 to 1.37). Additionally, the probability of a previous study being described by the recent meta-analysis was inversely associated with the concordance of results (odds ratio, 0.38; 95% confidence interval, 0.17 to 0.88), and the probability of being discussed was increased for previous studies that employed meta-analytic methods (odds ratio, 32.36; 95% confidence interval, 2.00 to 522.85).

CONCLUSIONS

Meta-analyses on pharmacological treatments do not consistently refer to and discuss findings of previous meta-analyses on the same topic. Such neglect can lead to research waste and be confusing for readers. Journals should make the discussion of related meta-analyses mandatory.

Overview of the new oral anticoagulants: opportunities and challenges

The non-vitamin K antagonist oral anticoagulants (NOACs) are replacing warfarin for many indications. These agents include dabigatran, which inhibits thrombin, and rivaroxaban, apixaban, and edoxaban, which inhibit factor Xa. All 4 agents are licensed in the United States for stroke prevention in atrial fibrillation and for treatment of venous thromboembolism and rivaroxaban and apixaban are approved for thromboprophylaxis after elective hip or knee arthroplasty. The NOACs are at least as effective as warfarin, but are not only more convenient to administer because they can be given in fixed doses without routine coagulation monitoring but also are safer because they are associated with less intracranial bleeding. As part of a theme series on the NOACs, this article (1) compares the pharmacological profiles of the NOACs with that of warfarin, (2) identifies the doses of the NOACs for each approved indication, (3) provides an overview of the completed phase III trials with the NOACs, (4) briefly discusses the ongoing studies with the NOACs for new indications, (5) reviews the emerging real-world data with the NOACs, and (6) highlights the potential opportunities for the NOACs and identifies the remaining challenges.

A systematic review and adjusted indirect comparison of oral anticoagulants

EDUCATIONAL OBJECTIVES As a result of reading this article, physicians should be able to: 1. Recognize the high risk of postoperative venous thromboembolism (VTE) in patients undergoing major orthopedic surgery. 2. Distinguish the different pharmacological mechanisms of VTE prophylaxis drugs. 3. Delineate the advantages and disadvantages of each VTE prophylaxis drug. 4. Recognize that rivaroxaban is as efficacious as apixaban but can increase the risk of hemorrhage. Patients undergoing major orthopedic surgery are at high risk for developing postoperative venous thromboembolism (VTE). The authors analyzed the available evidence on the efficacy and safety of dabigatran, apixaban, and rivaroxaban vs low-molecular-weight heparins (LMWHs) as VTE prophylaxis in major orthopedic surgery. Outcomes evaluated included total VTE, deep venous thrombosis (DVT), pulmonary embolism (PE), death, and major bleeding. Rivaroxaban and apixaban are more efficacious than dabigatran and are as safe as dabigatran. Rivaroxaban is as efficacious as apixaban but can increase the risk of hemorrhage.

Expanding use of new oral anticoagulants

New, non-vitamin K antagonist oral anticoagulants (NOACs) have been developed to overcome the limitations of warfarin. These include dabigatran, which inhibits thrombin, and rivaroxaban, apixaban, and edoxaban, which inhibit factor Xa. In the US, rivaroxaban and apixaban are licensed for thromboprophylaxis after elective hip or knee arthroplasty, and rivaroxaban and dabigatran are approved for treatment of venous thromboembolism. Dabigatran, rivaroxaban, and apixaban also are licensed for stroke prevention in eligible patients with atrial fibrillation. Designed to be given in fixed doses without routine coagulation monitoring, the NOACs are more convenient to administer than warfarin. Phase III clinical trials have shown that the NOACs are at least as effective as warfarin and are associated with less intracranial bleeding. This article compares the pharmacological properties of the NOACs with those of warfarin, describes the clinical trial data with the NOACs in the approved indications, outlines the unmet medical needs that the NOACs address, highlights the potential limitations of the NOACs, and provides guidance on the optimal use of the NOACs.

A checklist for critical appraisal of indirect comparisons

The aim of this study was to develop a user-friendly checklist for critical appraisal of indirect comparisons of drugs, considering clinical, methodological/statistical and quality aspects, mainly to be applied in drug evaluation in the decision-making context. After conducting a review of the literature, we used group consensus to establish the key points of the checklist, focusing mainly on indirect comparisons, but including topics related to network meta-analysis or multiple treatment comparisons. The coordinating group elaborated the first draft, which was reviewed by external experts, re-evaluated by the coordinating group and finally assessed by 23 drug evaluation experts trained in indirect comparisons, who applied the checklist to one study. The Kappa index of agreement was calculated and the final checklist was developed by group consensus including the external experts. The checklist has two parts. The first consists of three eliminatory key questions while the second includes 17 items: 5 regarding quality, 5 regarding clinical issues and 7 dealing with methodology/statistics. The median kappa values of the 23 evaluations were 0.83 (range 0.67-0.93), 0.61 (0.54-0.91) and 0.36 (0.22-1) with regard to quality, clinical aspects and methodology/statistics, respectively. A structured checklist was developed to facilitate critical appraisal of key issues in indirect comparisons, including comments for assessing the consequences of its application to drug evaluation in the decision-making context. Agreement between reviewers in clinical and quality items was good, but weaker in methodology/statistics ones.

New oral pharmacotherapeutic agents for venous thromboprophylaxis after total hip arthroplasty

Patients undergoing total hip arthroplasty (THA) are at high risk for developing venous thromboembolism and, therefore, require short term prophylaxis with antithrombotic agents. Recently, target specific oral anticoagulants (TSOA) including the direct thrombin inhibitor, dabigatran, and the factor Xa inhibitors rivaroxaban, apixaban, and edoxaban have been approved for THA thrombopropylaxis in various countries. The TSOAs provide a rapid acting, oral alternative to parenteral agents including low-molecular weight heparins (LMWH) and fondaparinux; and compared to warfarin, they do not require routine laboratory monitoring and possess much fewer drug-drug interactions. Based on phase III clinical studies, TSOAs have established themselves as an effective and safe option for thromboprophylaxis after THA compared to LMWH, particularly enoxaparin, but require additional evaluation in specific populations such as the renally impaired or elderly. The ability to monitor and reverse these TSOAs in the case of bleeding complications or suspected sub- or supra-therapeutic anticoagulation is of importance, but remains investigational. This review will focus on the drug-specific characteristics, efficacy, safety, and economic impact of the TSOAs for thromboprophylaxis following THA, as well as the aspects of therapeutic monitoring and anticoagulation reversal in the event of bleeding complications or a need for urgent reversal.

Anticoagulation; New Pharmacologic Methods to Prevent Venous Thromboembolism in Older Adults: A Meta-Analysis

OBJECTIVE

To conduct a meta-analysis of randomized controlled trials that used newly approved drugs to prevent venous thromboembolism (VTE) in older adults.

DATA SOURCES

PubMed, EMBASE, and International Pharmaceutical Abstracts (through July 2012).

STUDY SELECTION AND DATA EXTRACTION

Full-text clinical trial reports were included if they (1) had a randomized controlled design, (2) used a pharmacologic method approved or anticipated to be approved in the US, (3) enrolled at least 300 subjects, (4) enrolled subjects with a mean age of 65 years or older or performed a subgroup analysis in adults in that population, and (5) scored at least 7 of 8 on quality criteria for clinical trials. Twenty unique studies met the inclusion criteria.

DATA SYNTHESIS

The most common indications for pharmacologic VTE prophylaxis in the identified studies were orthopedic procedures involving the lower extremities and general surgery. Only 2 studies enrolled acutely ill patients admitted to hospital medical services. Fondaparinux (5 studies) was more effective than enoxaparin in preventing VTE (OR 0.5, 95% CI 0.37–0.67; p < 0.00001) but had more bleeding (OR 1.48, 95% CI 1.05–2.08; p = 0.03). Dabigatran 150 mg once daily (3 studies) was less effective than enoxaparin in preventing VTE (OR 1.30, 95% CI 1.09–1.56; p = 0.004) with a similar bleeding risk (OR 0.74, 95% CI 0.46–1.22; p = 0.24). Dabigatran 220 mg once daily (4 studies) was as effective as enoxaparin in preventing VTE (OR 1.02, 95% CI 0.83–1.26; p = 0.84) and had similar bleeding (OR 1.08, 95% CI 0.66–1.76; p = 0.76). Rivaroxaban (4 studies) was more effective than enoxaparin in preventing VTE (OR 0.38, 95% CI 0.23–0.61; p < 0.0001) with a trend toward a higher rate of bleeding (OR 1.8, 95% CI 0.90–3.60; p = 0.09). Apixaban (5 studies) was more effective than enoxaparin in preventing VTE (OR 0.64, 95% CI 0.43–0.96; p = 0.0002) and had a similar rate of bleeding (OR 0.71, 95% CI 0.42–1.21; p = 0.21).

CONCLUSIONS

When compared to enoxaparin, newer drugs exhibit slightly different safety and efficacy profiles when used for VTE prevention in older adults undergoing major orthopedic surgery. There are insufficient data for other indications. The benefits and risks of new pharmacologic methods of VTE prevention are unclear in the oldest old (age ≥85 years) and in those admitted to a hospital for an acute medical illness or to a skilled nursing facility.

Clinical trials with new oral anticoagulants. Additive value of indirect comparisons also named network meta-analyses

To compare the efficacy and safety of the new oral anticoagulants (NOAC), ideally head-to-head clinical trials should be performed. Given the expense of such an undertaking, it is highly unlikely that such a comparison would be performed. Therefore, there is a need for an unbiased comparative assessment of the benefits and risks of the NOACs, based on the available trial data. Indirect or mixed treatment comparisons may be an useful tool to overcome these limitations also known as network meta-analysis (NMA). The aim of this paper is to give an overview on published NMAs for dabigatran, rivaroxaban and apixaban, each assessed against warfarin in patients with atrial fibrillation, and against enoxaparin in patients undergoing total knee and total hip replacement surgery, in order to obtain insights into the comparability of the adopted methodological techniques.

Direct treatment comparison of DAbigatran and RIvaroxaban versus NAdroparin in the prevention of venous thromboembolism after total knee arthroplasty surgery: design of a randomised pilot study (DARINA)

INTRODUCTION

Two novel agents, dabigatran and rivaroxaban, recently gained market authorisation for prevention of venous thromboembolism (VTE) after hip and knee arthroplasty. However, safety data of the new oral anticoagulants with a long-term use of 42 days are not available for total knee arthroplasty (TKA). Furthermore, there are no clinical trials comparing dabigatran and/or rivaroxaban with nadroparin, which is used in most Dutch departments of orthopaedic surgery. Our aim is to compare the 42-day use of dabigatran and rivaroxaban versus nadroparin after TKA in a clinical explorative pilot study by assessing the incidence of major bleeding and clinically relevant non-major bleeding using a standardised model of bleeding definitions.

METHODS AND ANALYSIS

A randomised open-label pilot study was conducted. Patients ≥18 years and weighing more than 40 kg who were scheduled for a primary elective TKA were included. Patients were randomly assigned to three groups. Patients took either a daily oral dose of dabigatran etexilate 220 mg (n=50), 10 mg of oral rivaroxaban (n=50) or subcutaneous nadroparin 0.3 ml (n=50) for 42 days. The primary safety outcome measure was the incidence of bleeding events. Major bleeding events and clinically relevant non-major bleeding events were defined according to accepted guidelines. The secondary measures of this study were the occurrence of VTE, time until the bleeding event, compliance, duration of hospital stay, rehospitalisation, outpatient clinic visits and interventions following complications. Additionally, coagulation monitoring, knee flexion range of motion and Knee injury and Osteoarthritis Outcome Score were evaluated.

DISSEMINATION

The results of this trial provided insight into the validity of design for an adequately powered multicentre study investigating the safety of the new oral anticoagulants compared with nadroparin, an anticoagulant applied for prevention of VTE after knee arthroplasty in the Dutch situation.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov: NCT01431456.

Efficacy and safety of novel oral anticoagulants for treatment of acute venous thromboembolism: direct and adjusted indirect meta-analysis of randomised controlled trials

OBJECTIVE

To critically review the effectiveness of the novel oral anticoagulants (rivaroxaban, dabigatran, ximelagatran, and apixaban) in the treatment of acute venous thromboembolism.

DESIGN

Systematic review and random effects meta-analysis. Data were extracted independently by two investigators. An adjusted indirect comparison was performed to compare between novel oral anticoagulants.

DATA SOURCES

Medline, Embase, and Cochrane Library (from inception to April 2012). Hand searching of relevant scientific works and contact with experts.

STUDY SELECTION

Randomised controlled trials of novel oral anticoagulants compared with vitamin K antagonists for acute venous thromboembolism. Selected outcomes were recurrent events, major bleeding, and all cause mortality.

RESULTS

Nine studies met our inclusion criteria, involving 16,701 patients evaluated for efficacy and 16,611 for safety. Data were stratified according to different novel oral anticoagulants. For recurrent acute venous thromboembolism, there were no significant differences in events rates between any of the anticoagulants and conventional treatment (rivaroxaban (four studies): relative risk 0.85, 95% confidence interval 0.55 to 1.31; dabigatran (two studies): 1.09, 0.76 to 1.57; ximelagatran (two studies): 1.06, 0.62 to 1.80; and apixaban (one study): 0.98, 0.20 to 4.79). Rivaroxaban reduced the risk of major bleeding compared with conventional treatment (0.57, 0.39 to 0.84), whereas other novel oral anticoagulants did not (0.76 (0.49 to 1.18) for dabigatran; 0.54 (0.28 to 1.03) for ximelagatran; 2.95 (0.12 to 71.82) for apixaban). For all cause mortality there were no significant differences between the novel oral anticoagulants and conventional treatment (0.96 (0.72 to 1.27) for rivaroxaban; 1.00 (0.67 to 1.50) for dabigatran; 0.67 (0.42 to 1.08) for ximelagatran; 6.89 (0.36 to 132.06) for apixaban). The adjusted indirect comparison between rivaroxaban and dabigatran did not show superiority of either drug over the others for major bleeding (0.75, 0.41 to 1.34) or the other endpoints.

CONCLUSIONS

Compared with vitamin K antagonists, the novel oral anticoagulants had a similar risk of recurrence of acute venous thromboembolism and all cause mortality, though rivaroxaban was associated with a reduced risk of bleeding.

Venous thromboembolism: diagnosis and current anticoagulation strategies for deep vein thrombosis and pulmonary embolism

The diagnosis and treatment of venous thromboembolic events represents a significant source of medical spending, both domestically and worldwide. Advances in medical imaging and pharmacology continue to alter and improve established treatment paradigms. In this article, we discuss venous thromboembolism etiology, diagnosis, and rationale for current and future treatment strategies.

A 12 month review of a modified protocol using low dose Dabigatran Etexilate in postoperative thromboembolic prophylaxis in joint replacement surgery

Background

Venous Thrombo-embolic disease is currently a hot topic especially in the UK. 25,000 patients per year die of Pulmonary Emboli (PE) in the United Kingdom (UK). Hip and knee arthroplasty surgery is associated with an increased rate of deep vein thrombosis (DVT) and pulmonary embolus (PE). The National Institute for Clinical Excellence (NICE) guidelines introduced in January 2010 recommended use of subcutaneous heparin or an oral anticoagulant (Dabigatran or Rivaroxiban) for 10-14 days post knee and 28-35 days post hip arthroplasty. In our unit we were keen on the advantages of an oral anticoagulant post arthroplasty in terms of patient compliance, and avoiding the need for self administered injection in the community.

Methods

We analysed all the notes, blood results and imaging of patients undergoing total hip or knee arthroplasty and present 1 year’s data using a regime of subcutaneous Dalteparin whilst an inpatient, followed by discharge on oral Dabigatran at a low dose (150 mg once daily).

Results

There were 337 patients over 1 year with hip and knee arthroplasty, with a 1.19% rate of DVT with no PEs and 1 death due to an unrelated cause. There was a transfusion rate of 11.57% with 1.19% patients taken back to theatre for evacuation of haematomas. There were no reported adverse effects of Dabigatran.

Conclusion

Our treatment protocol is a novel practical approach for VTE prophylaxis in hip and knee replacement patients. This approach shows promising data but no definitive evidence to warrant wide-spread use of this new regime. This data can act as a foundation for larger randomised clinical trials.

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.

Dabigatran, rivaroxaban, or apixaban versus enoxaparin for thromboprophylaxis after total hip or knee replacement: systematic review, meta-analysis, and indirect treatment comparisons

OBJECTIVE

To analyse clinical outcomes with new oral anticoagulants for prophylaxis against venous thromboembolism after total hip or knee replacement.

DESIGN

Systematic review, meta-analysis, and indirect treatment comparisons.

DATA SOURCES

Medline and CENTRAL (up to April 2011), clinical trials registers, conference proceedings, and websites of regulatory agencies.

STUDY SELECTION

Randomised controlled trials of rivaroxaban, dabigatran, or apixaban compared with enoxaparin for prophylaxis against venous thromboembolism after total hip or knee replacement. Two investigators independently extracted data. Relative risks of symptomatic venous thromboembolism, clinically relevant bleeding, deaths, and a net clinical endpoint (composite of symptomatic venous thromboembolism, major bleeding, and death) were estimated using a random effect meta-analysis. RevMan and ITC software were used for direct and indirect comparisons, respectively.

RESULTS

16 trials in 38,747 patients were included. Compared with enoxaparin, the risk of symptomatic venous thromboembolism was lower with rivaroxaban (relative risk 0.48, 95% confidence interval 0.31 to 0.75) and similar with dabigatran (0.71, 0.23 to 2.12) and apixaban (0.82, 0.41 to 1.64). Compared with enoxaparin, the relative risk of clinically relevant bleeding was higher with rivaroxaban (1.25, 1.05 to 1.49), similar with dabigatran (1.12, 0.94 to 1.35), and lower with apixaban (0.82, 0.69 to 0.98). The treatments did not differ on the net clinical endpoint in direct or indirect comparisons.

CONCLUSIONS

A higher efficacy of new anticoagulants was generally associated with a higher bleeding tendency. The new anticoagulants did not differ significantly for efficacy and safety.

New oral anticoagulants: will they replace warfarin?

Vitamin K antagonists, such as warfarin, are considered to be the treatment of choice to prevent thromboembolic events, but problems, such as the need for frequent dose adjustment and monitoring of coagulation status, as well as multiple drug and food interactions, make their use difficult for both physician and patient. Two new anticoagulants are now being considered as possible replacements of vitamin K antagonists. Dabigatran, an oral direct thrombin inhibitor has already been approved in the USA for prevention of stroke in patients with atrial fibrillation. Rivaroxaban, a factor Xa inhibitor, and dabigatran are licensed in Europe and Canada for short-term thromboprophylaxis after elective hip or knee replacement surgery. The advantages of these drugs are that they are safe and effective, require no monitoring, have a direct mode of action against only one clotting factor (thrombin or factor Xa), have limited drug interactions, and have rapid peak blood levels. Based on the fact that dabigatran has already been approved for use in the USA, it would appear that it has an advantage over rivaroxaban in becoming the replacement drug for vitamin K antagonists.

The Efficacy and Safety of Pharmacological Prophylaxis of Venous Thromboembolism Following Elective Knee or Hip Replacement

The present systematic review was conducted to assess the efficacy and safety of apixaban versus other anticoagulants, for the prevention of venous thromboembolism (VTE) following total hip replacement (THR) and total knee replacement (TKR) surgery. Electronic databases were interrogated to identify relevant randomized controlled trials. A series of direct/indirect comparisons and a network meta-analysis were conducted. Indirect comparisons found that the odds ratio of “all VTE and all-cause death” were significantly higher for dabigatran than for apixaban in patients with THR (odds ratio [OR], 2.51; 95% confidence interval [CI], 1.50-4.21) and TKR (OR, 1.72; 95% CI, 1.22-2.42). Rivaroxaban showed similar efficacy to apixaban in patients with THR and TKR (OR, 0.69; 95% CI, 0.38-1.25 and OR, 0.83; 95% CI, 0.57-1.19, respectively). No significant differences were observed in bleeding outcomes between treatments. The novel anticoagulants apixaban, rivaroxaban, and dabigatran demonstrated similar or improved efficacy and similar safety compared with current therapies in this indication.

New anticoagulants: how to deal with treatment failure and bleeding complications

Conventional anticoagulants have proven efficacy in the management of thromboembolism. Their adverse effects and a narrow therapeutic window, necessitating regular need for monitoring, however, have long been an incentive for the development of safer anticoagulants without compromising efficacy. Over the last decade or so several new parenteral and oral anticoagulants have been launched with efficacy comparable with conventional agents. From fondaparinux to its long acting derivative idraparinux, and the factor Xa inhibitor rivaroxaban to the direct thrombin inhibitor dabigatran, the advent of new anticoagulants is radically changing anticoagulation. For conventional anticoagulants, despite their shortcomings, effective methods of reversing their anticoagulant effects exist. Moreover, strategies to deal with the occurrence of fresh thrombotic events in the face of therapeutic anticoagulation with the conventional agents have also been addressed. Nevertheless, for the new anticoagulants, the optimal management of these complications remains unknown. This review explores these issues in the light of current evidence.

Assessing the comparative effectiveness of newly marketed medications: methodological challenges and implications for drug development

Comparative-effectiveness research (CER) aims to produce actionable evidence regarding the effectiveness and safety of medical products and interventions as they are used outside of controlled research settings. Although CER evidence regarding medications is particularly needed shortly after market approval, key methodological challenges include (i) potential bias due to channeling of patients to the newly marketed medication because of various patient-, physician-, and system-related factors; (ii) rapid changes in the characteristics of the user population during the early phase of marketing; and (iii) lack of timely data and the often small number of users in the first few months of marketing. We propose a mix of approaches to generate comparative-effectiveness data in the early marketing period, including sequential cohort monitoring with secondary health-care data and propensity score (PS) balancing, as well as extended follow-up of phase III and phase IV trials, indirect comparisons of placebo-controlled trials, and modeling and simulation of virtual trials.

Vitamin K antagonists--current concepts and challenges

Vitamin K antagtonists (VKAs) have, for decades, been the corner-stone of anticoagulation in the outpatient setting. While the long half life makes once daily administration practical, close monitoring of VKA effect is necessary because these medicines have a narrow therapeutic index. Despite inter-individual variations in response to VKA doses, the increasing availability of specialized anticoagulation monitoring systems, along with a better understanding of potential drug and dietary interactions, has made the use of VKAs safer and less burdensome. In the future, newer classes of oral anticoagulants and genomic-based dosing strategies may further expand or improve the management options for many patients at risk for thromboembolism.