Extended use of dabigatran, warfarin, or placebo in venous thromboembolism

Rivaroxaban for the treatment of pulmonary embolism

With the advent of new oral anticoagulants (NOACs) for the treatment of deep-vein thrombosis (DVT) and/or pulmonary embolism (PE), a new era of oral anticoagulation for patients with venous thromboembolism (VTE) has begun. Rivaroxaban is the first NOAC to receive regulatory approval for the acute and continued treatment of DVT and PE, and for the secondary prevention of VTE. Here, the clinical trials of rivaroxaban in patients with VTE are reviewed, and the clinical use of rivaroxaban for patients with PE is discussed. Even though rivaroxaban will facilitate the therapeutic management of PE, its use in specific clinical situations needs further study.

Optimal treatment duration of venous thrombosis

Randomized controlled trials have shown that patients with venous thromboembolism benefit from a minimum of three months of anticoagulant therapy. After this period, it was suggested that patients with an expected annual recurrence rate of < 5% could safely discontinue treatment. Using a population-based approach for stratification, these patients are those with major transient risk factors, and represent the minority. For all other patients, including those with previous episodes of venous thromboembolism, cancer, or unprovoked events, this treatment duration may not be sufficiently protective. Because extending anticoagulation for additional three to nine months does not result in further, long-term reduction of recurrences, indefinite treatment duration should be considered. However, case-fatality rate for major bleeding in patients taking warfarin for more than three months is higher than case-fatality rate of recurrent venous thromboembolism. Thus, an individual patient approach to improve and increase the identification of those who can safely discontinue treatment at three months becomes necessary. Clinical prediction rules or management strategies based on D-dimer levels or residual vein thrombosis have been proposed and need further refinement and validation. Specific bleeding scores are lacking. Meanwhile, the oral direct inhibitors have been proposed as potential alternatives to the vitamin K antagonists, and aspirin may provide some benefit in selected patients who discontinue anticoagulation. Deep vein thrombosis in unusual sites is associated with less, but potentially more severe recurrences, in particular in patients with splanchnic vein thrombosis who also face an increased risk of bleeding complications while on treatment.

Oral anticoagulants in the management of venous thromboembolism

Despite advances in diagnosis, prevention, and management, venous thromboembolism (VTE) remains a common cause of morbidity and mortality. For decades, antithrombotic therapy for prevention and treatment of VTE was limited to parenteral agents related to heparin and oral vitamin K antagonists (VKAs). Both classes of anticoagulants are effective, but have limitations, including considerable variability in dose-response, narrow therapeutic margins between the risks of thrombosis and bleeding, and the need to monitor anticoagulation intensity. Over the past decade, the introduction of new oral anticoagulants that specifically inhibit coagulation factors IIa (thrombin) or Xa has changed practice in a variety of clinical situations, including VTE prophylaxis and treatment. In this Review, we outline the use of the novel oral anticoagulants apixaban, dabigatran, edoxaban, and rivaroxaban in the prevention and treatment of VTE, and discuss practical considerations for choosing the appropriate drug for each patient. Although the introduction of novel anticoagulant drugs is promising, selecting the optimum strategy for an individual patient requires an understanding of the specific circumstances associated with thrombus formation and the pharmacological properties of each agent.

Potential role of new anticoagulants for prevention and treatment of venous thromboembolism in cancer patients

Venous thromboembolism (VTE), encompassing deep vein thrombosis and pulmonary embolism, represents a major cause of morbidity and mortality in patients with cancer. Low molecular weight heparins are the preferred option for anticoagulation in cancer patients according to current clinical practice guidelines. Fondaparinux may also have a place in prevention of VTE in hospitalized cancer patients with additional risk factors and for initial treatment of VTE. Although low molecular weight heparins and fondaparinux are effective and safe, they require daily subcutaneous administration, which may be problematic for many patients, particularly if long-term treatment is needed. Studying anticoagulant therapy in oncology patients is challenging because this patient group has an increased risk of VTE and bleeding during anticoagulant therapy compared with the population without cancer. Risk factors for increased VTE and bleeding risk in these patients include concomitant treatments (surgery, chemotherapy, placement of central venous catheters, radiotherapy, hormonal therapy, angiogenesis inhibitors, antiplatelet drugs), supportive therapies (ie, steroids, blood transfusion, white blood cell growth factors, and erythropoiesis-stimulating agents), and tumor-related factors (local vessel damage and invasion, abnormalities in platelet function, and number). New anticoagulants in development for prophylaxis and treatment of VTE include parenteral compounds for once-daily administration (ie, semuloparin) or once-weekly dosing (ie, idraparinux and idrabiotaparinux), as well as orally active compounds (ie, dabigatran, rivaroxaban, apixaban, edoxaban, betrixaban). In the present review, we discuss the pharmacology of the new anticoagulants, the results of clinical trials testing these new compounds in VTE, with special emphasis on studies that included cancer patients, and their potential advantages and drawbacks compared with existing therapies.