New oral anticoagulants for the treatment of venous thromboembolism: understanding differences and similarities

Evaluation of Anti-Xa Apixaban and Rivaroxaban Levels With Respect to Known Doses in Relation to Major Bleeding Events

BACKGROUND

Although not routinely recommended, anti-Xa level monitoring for apixaban or rivaroxaban may be useful in certain clinical scenarios. There are currently no laboratory standards, therapeutic ranges, or proven correlation between anti-Xa levels and clinical outcomes.

OBJECTIVE

This study describes the utilization, application, and association of anti-Xa levels with clinical outcomes in patients receiving apixaban or rivaroxaban.

METHODS

This retrospective, descriptive study included adult inpatients within the Houston Methodist System on apixaban or rivaroxaban with at least one anti-Xa level ordered subsequent to administered doses. The primary endpoint was major bleeding according to International Society on Thrombosis and Haemostasis criteria. Secondary endpoints included reasons for anti-Xa level ordering, anti-Xa levels at different time intervals post-dose, and thrombotic events. Pre-specified subgroup analyses were performed to further evaluate the primary endpoint.

RESULTS

The study population consisted of 169 patients and 234 anti-Xa levels. Twenty-nine levels were obtained in context of major bleeding. The majority of levels were not drawn as peak levels 2-4 hours post-dose, however remained quantifiable above typical observed levels within this timeframe and well beyond 24 hours post-dose. Patient characteristics with major bleeding included elderly age, acute renal impairment, and low body weight. At least 14 unique reasons for anti-Xa level ordering were identified. Twenty-nine levels were associated with thrombotic events.

CONCLUSION

Anti-Xa levels may be useful for assessment of current drug concentrations, immediate safety of therapy, and guidance for possible clinical interventions. Dose titration and reversal therapies based on anti-Xa level results in major bleeding warrant further research.

Splanchnic vein thrombosis: Clinical manifestations, risk factors, management, and outcomes

BACKGROUND

Clinical manifestations and optimal management strategies in patients with splanchnic vein thrombosis (SVT) are not well characterized.

METHODS

We conducted a retrospective cohort study including all newly diagnosed SVT evaluated between January 2007 and December 2018. Efficacy outcome was thrombosis resolution, and safety outcomes included death and occurrence of bleeding.

RESULTS

We included 155 patients with a mean age of 56.2 (18-87). Local risk factors were present in 118 (76.1%) patients and 30 (19.4%) had only systemic/thrombophilia. Local risk factors included abdominal cancers (31%), surgery (20.6%) and liver cirrhosis (19.4%). Thrombophilia screening was conducted in approximately 50% of patients. Factor V Leiden or Prothrombin G20210A mutations were observed in 7.1% of patients whereas 14.4% were JAK2V617F mutation positive. Most common manifestations at onset were abdominal pain (56.1%), whereas 44.6% were incidentally found. Portal vein thrombosis was observed more in primary cases (91.9% vs. 69.5%, p = 0.012). Anticoagulation was used in 93.5% cases. Indefinite anticoagulation was used more frequently in primary SVT (62.2% vs. 41.5%, p = 0.045). Thrombosis resolution and bleeding complications among primary (without local risk factors) and secondary (with local risk factors) SVT were observed in 48.5%, 65%, 8.1%, and 11.9%, respectively with no difference when comparing patients treated with direct oral anticoagulants or warfarin and/or low molecular weight heparin (58% vs. 62%, p = 0.326, 9% vs. 12%, p = 0.518).

CONCLUSIONS

In this cohort anticoagulation resulted in partial or complete thrombosis resolution in a significant proportion of patients with an acceptable bleeding risk regardless local risk factors or type of anticoagulant.

ANMCO Position Paper: the use of non-vitamin K dependent new oral anticoagulant(s) in pulmonary embolism therapy and prevention

The new oral anticoagulants (NOACs) have radically changed the approach to the treatment and prevention of thromboembolic pulmonary embolism. The authors of this position paper face, in succession, issues concerning NOACs, including (i) their mechanism of action, pharmacodynamics, and pharmacokinetics; (ii) the use in the acute phase with the 'double drug single dose' approach or with 'single drug double dose'; (iii) the use in the extended phase with demonstrated efficacy and with low incidence of bleeding events; (iv) the encouraging use of NOACs in particular subgroups of patients such as those with cancer, the ones under- or overweight, with renal insufficiency (creatinine clearance > 30 mL/min), the elderly (>75 years); (v) they propose a possible laboratory clinical pathway for follow-up; and (vi) carry out an examination on the main drug interactions, their potential bleeding risk, and the way to deal with some bleeding complications. The authors conclude that the use of NOACs both in the acute phase and in the extended phase is equally effective to conventional therapy and associated with fewer major bleeding events, which make their use in patients at higher risk of recurrences safer.

Recent Progress in Research on the Pathogenesis of Pulmonary Thromboembolism: An Old Story with New Perspectives

Pulmonary thromboembolism (PTE) is part of a larger clinicopathological entity, venous thromboembolism. It is also a complex, multifactorial disorder divided into four major disease processes including venous thrombosis, thrombus in transit, acute pulmonary embolism, and pulmonary circulation reconstruction. Even when treated, some patients develop chronic thromboembolic pulmonary hypertension. PTE is also a common fatal type of pulmonary vascular disease worldwide, but earlier studies primarily focused on the pathological changes in the blood component of the disease. With contemporary advances in molecular and cellular biology, people are becoming increasingly aware of coagulation pathways, the function of vascular smooth muscle cells, microparticles, and the inflammatory pathways that play key roles in PTE. Combined hypoxia and immune research has revealed that PTE should be regarded as a class of complex diseases caused by multiple factors involving the vascular microenvironment and vascular cell dysfunction.

Non-vitamin K Oral Anticoagulants Versus Warfarin for Patients with Atrial Fibrillation: Absolute Benefit and Harm Assessments Yield Novel Insights

BACKGROUND AND OBJECTIVES

Benefits and/or harms (including costs) of non-vitamin K oral anticoagulants (NOACs) versus warfarin therapy need appreciation in relative and absolute terms.

METHODS

Accordingly, we derived clinically relevant relative and absolute benefit/harm parameters for NOACs (apixaban, dabigatran, rivaroxaban, edoxaban) compared to warfarin from four clinical trials involving atrial fibrillation (AF) patients. For each trial, we tabulated patient numbers enduring four important outcomes and calculated unadjusted relative risk reduction (RRR) and number needed to treat (NNT)/year values (and 95% confidence intervals) for the NAOC compared to warfarin. These outcomes were as follows: stroke/systemic embolism (primary endpoint), hemorrhagic stroke, major bleeds, and death. We also addressed drug acquisition costs.

RESULTS

Each NOAC was noninferior to warfarin for primary-outcome prevention; RRRs were 12-33% and NNT/year values were 182-481, and all but one indicated statistically significant superiority. All the NOACs yielded statistically significant reductions in hemorrhagic stroke risk; RRRs were 42-74% and NNT/year values were 364-528. Major bleeding risk was comparable in both groups. Apixaban yielded a lower NNT/year for preventing death than for primary-outcome prevention. Compared to warfarin, NOAC acquisition costs were 70- to 140-fold greater.

CONCLUSIONS

For the primary outcome, the absolute benefits of NOACs were modest (NNT/year values being large). Reduced hemorrhagic stroke rates with NOACs could be due to superior embolic infarct prevention and fewer consequential hemorrhagic transformations. Among apixaban recipients, the absolute mortality benefit exceeded that for the primary outcome, indicating prevention of additional unrelated deaths. The substantially greater NOAC acquisition costs need viewing against probable greater safety and the avoidance of monitoring bleeding risks.

Possible failure of novel direct-acting oral anticoagulants in management of pulmonary embolism: a case report

Background

The relative effectiveness of vitamin K antagonists compared with novel oral anticoagulants in treating pulmonary embolism remains unclear. Recent trials comparing the efficacy of vitamin K antagonists with factor Xa inhibitors for the treatment of pulmonary emboli have been non-inferiority studies based primarily on risk reduction (such as bleeding events), rather than resolution of specific diseases such as pulmonary embolism. Consequently, there is a lack of evidence indicating which of these agents are more effective. Here, we present a case where pulmonary emboli were treated with novel oral anticoagulants followed by warfarin to discuss the potential limitations in the use of novel oral anticoagulants as prevention or treatment of thromboembolism and the continued role for warfarin in this setting.

Case presentation

A 34-year-old African American woman presented to our clinic with shortness of breath and pleuritic chest pain several months post-surgery. She was identified as having multiple bilateral pulmonary embolisms and was treated with several novel oral anticoagulants, which failed to resolve the clots. Complete resolution was achieved upon switching to warfarin.

Conclusions

The patient described in this report failed to respond to novel oral anticoagulant therapy, but her emboli resolved when she was treated with warfarin. This study challenges the notion that factor Xa inhibitors are better alternatives to vitamin K anticoagulants in the treatment of pulmonary emboli based on their safety profile and ease of use alone. As a result, further post-marketing investigations into the efficacy of these agents in the management of pulmonary emboli may be warranted.

Edoxaban: A Review in Deep Vein Thrombosis and Pulmonary Embolism

Edoxaban (Lixiana, Savaysa) is an oral, direct factor Xa inhibitor which has recently been approved for use in the treatment of deep vein thrombosis (DVT) and pulmonary embolism (PE) [collectively, venous thromboembolism (VTE)] and for the prevention of recurrent VTE. This article reviews the pharmacological properties of edoxaban as well as its tolerability and therapeutic efficacy in the treatment and prevention of recurrent VTE events. As demonstrated in the pivotal Hokusai-VTE phase III trial, once-daily edoxaban after initial treatment with heparin was non-inferior to standard therapy with heparin/warfarin in preventing recurrent VTE events and was associated with a significantly lower risk of clinically relevant bleeding than the traditional therapy. Edoxaban shares the advantages of other direct oral anticoagulants (DOACs) over traditional therapies, including the lack of requirement for routine coagulation monitoring, a rapid onset and offset of action, and few drug-drug interactions. It offers the convenience of once-daily dosing, can be taken without regard to food and allows for a dose reduction in patients with certain clinical features, such as moderate renal impairment or low body weight. In conclusion, edoxaban represents an effective and potentially safer alternative to traditional vitamin K antagonist therapy for the treatment and prevention of recurrent VTE. Its recent approval expands the range of DOAC agents for recurrent VTE, further facilitating treatment individualization.

Synthesis, Crystal Structural, and Spectral Characterisation of Dabigatran Etexilate Tetrahydrate

Dabigatran etexilate tetrahydrate, C34H49N7O9, has been crystallised at ambient conditions. The colourless crystal was investigated using X-ray crystallography with single crystals and powder techniques, and was characterised by thermogravimetric-differential thermal analysis (TG-DTA) and infrared spectroscopy (IR). The compound was shown to be a tetrahydrate. A dabigatran etexilate molecule and four water molecules form a large ring structure, and intra-molecular hydrogen bonds contribute to the formation of a stable molecule in the unit cell.

Management of Venous Thromboembolism: Recent Advances in Oral Anticoagulation Therapy

OBJECTIVE

To review clinical data on direct oral anticoagulants (DOACs) used in the acute treatment of venous thromboembolism (VTE) as well as practical considerations when using these products.

DATA SOURCES

Searches of PubMed and Google Scholar for VTE, deep vein thrombosis, pulmonary embolism, and relevant drug international nonproprietary names were conducted. Additional online searches were conducted for prescribing information.

STUDY SELECTION AND DATA EXTRACTION

Relevant articles on dabigatran, rivaroxaban, apixaban, and edoxaban for the management of VTE compared with oral vitamin K antagonists (VKAs; published between 1966 and December 2015) were reviewed and summarized, together with information on dosing, pharmacokinetics/pharmacodynamics, and drug-drug interactions.

DATA SYNTHESIS

The DOACs have the potential to circumvent many of the disadvantages of VKAs. At a minimum, they greatly increase the available therapeutic options, thus providing a greater opportunity for clinicians to select a management option that best fits the needs of individual patients. Despite the significant advance that DOACs represent, they are not without risk and require careful consideration of a number of clinical issues to optimize safety and efficacy.

CONCLUSIONS

The emergence of DOACs for the management of thromboembolic disorders represents a paradigm shift from oral VKAs. The DOACs provide similar efficacy and improved safety in selected patients as compared with VKAs. Clinicians treating VTE need to be familiar with the intricacies involved in using these agents, including the appropriate dose selection for the relevant indication, avoidance of drug-drug and drug-disease interactions, and consideration of dose adjustments in specific clinical situations, such as organ dysfunction.

Critical appraisal of dabigatran in the treatment of deep vein thrombosis and pulmonary embolism

OBJECTIVE

To compare the safety and efficacy of dabigatran to warfarin for the treatment of deep vein thrombosis and pulmonary embolism.

BACKGROUND

Venous thromboembolism (VTE) is a disease comprised of two conditions: deep vein thrombosis and pulmonary embolism. VTE is a major cause of morbidity and mortality worldwide with an annual incidence estimated at 1-3 cases per 1,000 individuals. This incidence increases with age from 0.1 per 1,000 in adolescence to eight per 1,000 in those 80 years of age and older. As the proportion of patients 65 years of age and older expands, the number of patients presenting with VTE will also increase. Anticoagulation remains the cornerstone of VTE treatment. Traditionally, vitamin K antagonists have been used to minimize the risk of thrombus extension and for secondary prevention. Unpredictable pharmacokinetics and pharmacodynamics, routine monitoring, drug-food and drug-drug interactions, and potentially severe adverse events have all been cited as barriers to optimal care. Dabigatran has been proposed as a suitable alternative to warfarin therapy in the treatment of VTE. Therefore, a critical appraisal of dabigatran's safety and efficacy is necessary to determine its role in therapy.

CONCLUSION

Dabigatran remains an alternative to warfarin therapy for the treatment of VTE. However, dabigatran also has distinct disadvantages that warrant consideration. Clinicians must ensure that drug characteristics align with patient characteristics to optimize patient outcomes.