Use of Emerging Oral Anticoagulants in Clinical Practice: Translating Results from Clinical Trials to Orthopedic and General Surgical Patient Populations

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.

Rivaroxaban differentially influences ex vivo global coagulation assays based on the administration time

It was the objective of this study to quantify the effects of rivaroxaban administration on global coagulation parameters associated with routine clinical procedures, we collected plasma samples from patients undergoing major orthopaedic surgery receiving rivaroxaban at various time points after drug administration. Forty-seven patients received rivaroxaban (10 mg daily) for venous thromboembolism prophylaxis. Blood samples were collected at four different time points: A) before surgery; B) before drug administration at day 4–5 after surgery (steady state of rivaroxaban); C) 2 hours (h) after drug administration and D) 12 h after drug administration. The prothrombin time (PT), activated partial thromboplastin time (aPTT), thrombin time (TT), antithrombin (AT) level, fibrinogen level by Clauss method (FibC), and derived fibrinogen (dFIB) level were assessed with various reagents. At 2 h after rivaroxaban administration, the PT and aPTT clotting times were significantly prolonged to different extents up to 1.4 fold, whereas 12 h after drug administration, no significant effect was observed. Rivaroxaban administration had no influence on the TT or the FibC concentration. The dFIB assay was differentially affected by rivaroxaban when different reagents were tested. The AT assay dependent on thrombin activity was not influenced by rivaroxaban, whereas the AT levels dependent on factor Xa activity were significantly increased by rivaroxaban. Clinicians should be aware of the time-dependent influence of rivaroxaban on factor Xa-dependent routine coagulation assays. Therefore, routine coagulation parameters should be assessed directly before drug administration to keep the interaction of rivaroxaban low.

Incidence of hospital readmission in patients diagnosed with DVT and PE: clinical burden of recurrent events

BACKGROUND

Venous thromboembolism (VTE), which comprises deep-vein thrombosis (DVT) and pulmonary embolism (PE), is associated with significant morbidity and mortality and represents a considerable economic burden to the US healthcare system. Although it is well established that patients with an initial VTE are at increased risk for recurrent VTE, limited data exist on the clinical burden of a secondary DVT or PE event. The objective of this retrospective observational study was to conduct an epidemiologic evaluation, from a hospital perspective, of patients with an initial DVT or PE who experienced a recurrent event postdischarge requiring hospital readmission.

METHODS

Hospital claims containing DVT or PE as a primary diagnosis for hospitalisation during the period October 2009 to April 2013 were identified by retrospective analysis using the MarketScan database. The time to hospital readmission for DVT or PE was assessed using the MarketScan Treatment Pathways tool.

RESULTS

Of 214,901 patient admissions identified with a diagnosis of DVT or PE at hospital admission, approximately 4% were subsequently readmitted to the hospital with a diagnosis of PE (8217) or DVT (9138). Of all readmitted patients with a diagnosis of DVT on initial admission, 66% were rehospitalised with a diagnosis of DVT, and 34% were rehospitalised with a diagnosis of PE. Of all readmitted patients with a diagnosis of PE on initial admission, 63% were rehospitalised with a diagnosis of PE and 37% with a diagnosis of DVT. Of all hospital readmissions with a diagnosis of PE or DVT, 62% and 58% occurred within the first 30 days following an initial PE or DVT event, respectively.

CONCLUSIONS

The burden of DVT or PE is large, not only because of the initial hospitalisation event but also because of the high number of hospital readmissions, more than half of which occur within 30 days.

Patient-reported compliance with thromboprophylaxis using an oral factor Xa inhibitor (rivaroxaban) following total hip and total knee arthroplasty

This prospective study examines patient non-compliance (NC) for an oral factor Xa inhibitor (Rivaroxaban) when used as venous thromboembolic (VTE) prophylaxis following lower limb arthroplasty. A total of 3145 patients underwent surgery from May 2010 to December 2011. At 6 weeks patients completed an anonymous self-administered questionnaire. Postoperatively 2947 (94%, 2947/3145) received Rivaroxaban. 2824 (96%, 2824/2947) completed all in-hospital doses. Seven percent (203/2824) of patients did not attend the 6-week follow-up. Two thousand one hundred sixty-three (83%, 2163/2621) completed all prescribed doses, 98 (4%, 98/2621) were NC and 360 (14%, 360/2621) had incomplete data. Gender, age, body mass index and preoperative hemoglobin all correlated with NC (p < 0.05). Type and side of surgery did not correlate with compliance (p > 0.05). Patient-reported NC for Rivaroxaban is 4% which compares favorably to other VTE prophylaxis modalities.

The use of novel oral anticoagulants for thromboprophylaxis after elective major orthopedic surgery

Venous thromboembolism is a common cause of morbidity and mortality among patients undergoing elective orthopedic surgery. Due to the high incidence of venous thromboembolism in this setting, perioperative anticoagulation is the recommended approach for thromboprophylaxis. Low molecular weight heparin (LMWH), fondaparinux and warfarin are the agents commonly used for thromboprophylaxis. The well-recognized limitations of warfarin and the inconvenience and discomfort associated with the subcutaneous administration of low molecular weight heparin and fondaparinux inspired intense investigation to develop novel oral anticoagulants (NOACs) with more predictable pharmacokinetics, fewer drug interactions and no need for regular laboratory monitoring. Three NOACs have been demonstrated to be effective for thromboprophylaxis after total hip arthroplasty (THA) and total knee arthroplasty (TKA) in large randomized controlled trials. Here we review the pharmacology of rivaroxaban, dabigatran, and apixaban, summarize the major clinical trials of these agents in thromboprophylaxis after THA and TKA, and discuss the clinical factors to be considered by providers when selecting a NOAC for their patients.

Systematic review of randomized controlled trials of new anticoagulants for venous thromboembolism prophylaxis in major orthopedic surgeries, compared with enoxaparin

BACKGROUND

In the past 10 years, new anticoagulants (NACs) have been studied for venous thromboembolism (VTE) prophylaxis.

OBJECTIVE

To evaluate the risk/benefit profile of NACs versus enoxaparin for VTE prophylaxis in major orthopedic surgery.

METHODS

A systematic review of double-blind randomized phase III studies was performed. The search strategy was run from 2000 to 2011 in the main medical electronic databases in any language. Independent extraction of articles was performed by 2 authors using predefined data fields, including study quality indicators.

RESULTS

Fifteen published clinical trials evaluating fondaparinux, rivaroxaban, dabigatran, and apixaban were included. Primary efficacy (any deep vein thrombosis [DVT], nonfatal pulmonary embolism, or all-cause mortality) favored fondaparinux (relative risk [RR] 0.50; 95% CI, 0.39, 0.63) and rivaroxaban (RR, 0.50; 95% CI, 0.34, 0.73) over enoxaparin, although significant heterogeneity was observed in both series. The primary efficacy of dabigatran at 220 mg, apixaban, and bemiparin were similar, with RRs of 1.02 (95% CI, 0.86, 1.20), 0.63 (95% CI, 0.39, 1.01), and 0.87 (95% CI, 0.65, 1.17), respectively. The primary efficacy of dabigatran at 150 mg (RR, 1.20; 95% CI, 1.03, 1.41), was inferior to enoxaparin. The incidence of proximal DVT favored apixaban (RR, 0.45; 95% CI, 0.27, 0.75) only. Rivaroxaban (RR, 0.45; 95% CI, 0.27, 0,77) and apixaban (RR, 0.38; 95% CI, 0.16, 0.90) produced significantly lower frequencies of symptomatic DVT. The incidence of major VTE favored rivaroxaban (RR, 0.44; 95% CI, 0.25, 0.81), only. Bleeding risk was similar for all NACs, except fondaparinux (RR, 1.27; 95% CI, 1.04, 1.55), which exhibited a significantly higher any-bleeding risk compared with enoxaparin, and apixaban (RR, 0.88; 95% CI, 0.79, 0.99), which was associated with a reduced risk of any bleeding. Alanine amino transferase was significantly lower with 220 mg of dabigatran, (RR, 0.67; 95% CI, 0.79, 0.99) than with enoxaparin.

CONCLUSIONS

NACs can be considered alternatives to conventional thromboprophylaxis regimens in patients undergoing elective major orthopedic surgery, depending on clinical characteristics and cost-effectiveness. The knowledge of some differences concerning efficacy or safety profile, pointed out in this systematic review, along with the respective limitations, may be useful in clinical practice.

Healthcare burden associated with the post-thrombotic syndrome and potential impact of the new oral anticoagulants

Deep-vein thrombosis (DVT) can have a significant impact on a patient's life. In particular, the development of post-thrombotic syndrome as a long-term complication of DVT can have devastating consequences for the individual and impose a substantial economic burden on healthcare systems. Anticoagulants are the mainstay of DVT treatment; however, the current standard of care, a parenteral anticoagulant followed by a vitamin K antagonist, is associated with complex patient management, often resulting in suboptimal therapy. New, oral anticoagulants have been developed, and a direct thrombin inhibitor--dabigatran etexilate--and two direct Factor Xa inhibitors--rivaroxaban and apixaban--have completed and/or have ongoing phase III trials in the treatment of venous thromboembolism. These agents do not have the drawbacks of the vitamin K antagonists and hold promise for more effective treatment of DVT, possibly resulting in a reduction in the incidence of post-thrombotic syndrome.

Preventing venous thromboembolism following orthopedic surgery in the United States: impact of special populations on clinical outcomes

Clinical trials of anticoagulants often exclude special populations. We assessed the proportion of special populations in real-world orthopedic surgery and the incidence of venous thromboembolism (VTE)-related outcomes. Data on patients with hip (n = 11 483) or knee replacement (n = 19 390) were extracted from IMS' PharMetrics Patient-Centric Database. There was high prevalence of patients aged ≥75 years (20.3%), CYP3A4-inhibitor use (21.5%), and chronic warfarin use (9.5%). Venous thromboembolism events were increased with each increasing year of age (hip: odds ratio [OR] 1.02, 95% confidence interval [CI] = 1.01-1.03; knee: OR 1.01, 95%CI = 1.00-1.02) and chronic warfarin use (hip: OR 1.56, 95%CI = 1.13-2.17; knee: OR 1.33, 95%CI = 1.03-1.72); in hip patients with renal insufficiency (OR1.61, 95%CI=1.11-2.36); and in knee patients with atrial fibrillation (OR 1.41, 95%CI = 1.06-1.88). Major bleeding was higher in hip patients with hepatic impairment (OR 21.99, 95%CI = 2.04-236.62), each increasing year of age (OR 1.08, 95%CI = 1.01-1.15), and chronic warfarin use (OR 7.11, 95%CI = 1.16-43.46). Special populations are prevalent in real-world orthopedic surgery, which may impact VTE-related outcomes.

Incidence rates for thromboembolic, bleeding and hepatic outcomes in patients undergoing hip or knee replacement surgery

BACKGROUND

Data on clinical outcomes of patients in the general population undergoing knee replacement or hip replacement surgery are sparse.

OBJECTIVES

To conduct an observational study using insurance claims data to assess the incidence of selected clinical events following knee replacement or hip replacement surgery in the USA.

PATIENTS/METHODS

A total of 97,469 knee replacement patients and a total of 45,203 hip replacement patients were included during the period 2004-2008; the median age was 64 years, and 63% of knee replacement patients and 55% of hip replacement patients were women.

RESULTS

During a median follow-up of 70-71 days, the incidence rates in knee replacement patients and hip replacement patients were, respectively: ischemic stroke, 15 and 19 per 1000 person-years; acute coronary syndrome (ACS), 15 and 18 per 1000 person-years; bleeding events, 46 and 47 per 1000 person-years; venous thromboembolism (VTE), 64 and 45 per 1000 person-years; and hepatic events, one and one per 1000 person-years. Approximately 45% of knee replacement and hip replacement patients had no claims for outpatient anticoagulant therapy within 1 week after discharge from hospital.

CONCLUSIONS

Ischemic events such as stroke, ACS and VTE are important adverse events following knee replacement and hip replacement surgery. The results reported here can help in making challenging decisions regarding the clinical management of risks attributable to bleeding events and clotting events.

Novel anticoagulants: a discussion of clinical use in the treatment and prevention of venous thromboembolism

Traditional therapeutic oral anticoagulation strategies often require invasive dosing or monitoring. Vitamin K antagonists (VKAs) have a large number of interactions, delayed onset requires frequent dose monitoring, and they have a small margin between therapeutic dose and bleeding complications. Novel oral anticoagulants, such as dabigatran, rivaroxaban and apixaban, are being developed to prevent those VKAs drawbacks. Besides oral bioavailability, those compounds are designed to require minimal to no monitoring and have a favourable safety profile. This review reports efficacy and safety data of these compounds throughout clinical development, as well as new approaches for oral pharmacological management of venous thromboembolism.

Toll-like receptor 9 signaling is critical for early experimental deep vein thrombosis resolution

OBJECTIVE

Toll-like receptors (TLR) bridge innate immunity and host responses, including inflammation. Sterile inflammation such as a venous thrombus (Vt) may involve TLR signaling, including TLR9.

METHODS AND RESULTS

TLR9 signaling on thrombus resolution was investigated using a mouse model of stasis Vt. Vt were significantly larger in TLR9-/- mice compared with wild-type (WT) at 2 and 8 days, despite a 2-fold increase in thrombus polymorphonucleic neutrophils at 2 days and monocytes at 8 days, whereas thrombus collagen and neovascularization was 55% and 37% less, respectively, at 8 days. Coincidently, decreased fibrinogen and increased thrombin-antithrombin complex were observed in TLR9-/- mouse thrombi. Vein wall interferon-α, interleukin-1α, and interleukin-2 were significantly reduced in TLR9-/- mice compared with WT. Thrombus cell death pathway markers were not significantly altered at 2 days, but caspase-1 was reduced in TLR9-/- thrombi at 8 days. MyD88 confers TLR9 intracellular signaling, but MyD88-/- mice had Vt resolution similar to that of WT. However, inhibition of the NOTCH ligand δ-like 4 was associated with larger Vt. Finally, stimulation with a TLR9 agonist was associated with smaller Vt.

CONCLUSIONS

TLR9 signaling is integral for early and mid-Vt resolution through modulation of sterile inflammation, maintaining a TH1 milieu, and effects on the thrombosis pathway.

New and Generic Anticoagulants and Biosimilars: Safety Considerations

The recent health care changes and approval of a generic low-molecular-weight heparin (LMWH) by the US Food and Drug Administration (FDA) merit a review of the facts regarding the new and generic anticoagulants. Fatal hypotension from anaphylactoid type reactions following heparin administration was responsible for more than 149 deaths all over the world. Researchers detected a heparin-like semisynthetic contaminant, over-sulfated chondroitin sulfate (OSCS), that appeared to be intentional. Low-molecular-weight heparins are produced using unfractionated heparin and OSCS has been found in various batches of LMWHs. Some newer anticoagulants are claiming to be free from the need to monitor for therapeutic effect and bleeding risk. Therefore, monitoring assays are not being developed and there is no antidote to reverse bleeding. In addition, there are concerns about reproducibility, product variation, and quality. In conclusion, although the generic LMWHs and newer anticoagulants may appear to be effective for qualified indications, their safety remains to be a concern.

Rivaroxaban vs dabigatran for thromboprophylaxis after joint-replacement surgery: exploratory indirect comparison based on meta-analysis of pivotal clinical trials

AIM

To indirectly compare rivaroxaban and dabigatran for prevention of venous thromboembolism (VTE) after total hip or knee arthroplasty (THA, TKA) based on their pivotal efficacy/safety trials embracing a total of 20618 patients.

METHODS

Pooled risk differences (RD) for rivaroxaban vs enoxaparin and dabigatran vs enoxaparin obtained from separate meta-analyses of two sets of trials were used to indirectly estimate RDs for rivaroxaban vs dabigatran.

RESULTS

Primary efficacy (any VTE+all-cause mortality) and safety (major bleeding) outcomes in enoxaparin arms largely differed across similarly designed rivaroxaban and dabigatran trials (differences in venography adjudication and bleeding events definitions). However, incidence of symptomatic VTE and incidence of major/non-major clinically relevant bleeding (including surgical site) were consistent in this respect. RDs (as percentages) for symptomatic VTE were: rivaroxaban-enoxaparin=-0.4% (95% confidence interval [CI], -0.9 to 0.05); dabigatran-enoxaparin=-0.09% (95% CI, -1.0 to 0.8); rivaroxaban-dabigatran=-0.3% (95% CI, -1.3 to 0.7; P=0.275). RDs for major/clinically relevant bleeding were rivaroxaban-enoxaparin=0.99% (95%CI, 0.29 to 1.69); dabigatran-enoxaparin=0.02% (95% CI, -1.0 to 1.0); rivaroxaban-dabigatran=0.97 (95% CI, -0.43 to 2.37; P=0.085). Mortality rates (all-cause, VTE-related, bleeding-related) were very low not indicating differences between any two of the three treatments.

CONCLUSION

Methodological differences disable indirect comparisons of rivaroxaban vs dabigatran that would be based on major efficacy/safety outcomes of their pivotal trials. The two drugs do not seem to differ regarding incidence of symptomatic VTE. Risk of a relevant bleeding is higher with rivaroxaban than with enoxaparin and the same tendency exists also vs dabigatran. Direct rivaroxaban vs dabigatran comparisons in this setting are needed.

Emerging antithrombotic agents for thromboprophylaxis, clinical potential and patient considerations

Patients undergoing major orthopedic surgery, total hip arthroplasty (THA) and total knee arthroplasty (TKA) are at high risk of venous thromboembolism, manifesting as deep vein thrombosis or pulmonary embolism. The recommended pharmacologic treatment options for thromboprophylaxis after major orthopedic surgery include the vitamin K antagonists (VKAs eg, warfarin), low molecular weight heparins (LMWHs; eg, enoxaparin) and the synthetic pentasaccharide fondaparinux. Most clinics use some kind of thromboprophylaxis routinely. However, due to the frequent need for coagulation monitoring (VKAs) and subcutaneous injections (LMWHs and fondaparinux) barriers exist to prescribing prophylaxis after discharge from hospital. Targeting specific components of the coagulation cascade has yielded several new antithrombotic agents for use as thromboprophylaxis after THA or TKA. Two of these, dabigatran etexilate and rivaroxaban, have already reached the markets in the European Union member states and Canada. Both are administered by the oral route, once-daily fixed dose and without the need to monitor the anticoagulant effect. Whether these new drugs facilitate guideline adherence, particularly in the outpatient settings and thereby improve the overall clinical outcomes remains to be shown.