New oral anticoagulants in venous thromboembolism prophylaxis in orthopaedic patients: Are they really better?

Apixaban: a review of its use in the prevention of venous thromboembolism after knee or hip replacement surgery

Apixaban (Eliquis™) is an orally active and selective direct inhibitor of factor Xa indicated for twice-daily use in the EU for the prevention of venous thromboembolism (VTE) in adults who have had knee or hip replacement surgery. In this article, the pharmacological, clinical efficacy and tolerability data relevant to the use of apixaban in this indication are reviewed. Oral apixaban is a generally effective and well tolerated thromboprophylactic agent for use after major orthopaedic surgery. In the large, randomized, double-blind, phase III, noninferiority trials known as ADVANCE-2 and -3, apixaban 2.5 mg twice daily initiated after surgery was generally more effective in preventing VTE in patients undergoing knee or hip replacement surgery than subcutaneous enoxaparin sodium initiated before surgery at the EU recommended dosage of 40 mg once daily, with apixaban conferring this benefit without significantly increasing the risk of bleeding. However, when the same apixaban regimen was compared with the US recommended dosage regimen of subcutaneous enoxaparin sodium (30 mg twice daily, initiated after surgery) in patients undergoing knee replacement surgery in the similarly designed ADVANCE-1 trial, the thromboprophylactic efficacy of apixaban did not meet primary endpoint noninferiority criteria, although apixaban was associated with fewer major or clinically relevant nonmajor bleeds (composite endpoint) than this enoxaparin sodium regimen. Additional comparative efficacy and tolerability data are required to definitively position apixaban with respect to other anticoagulants, including rivaroxaban and dabigatran etexilate. In the meantime, currently available clinical data indicate that apixaban is an emerging option for the prevention of VTE in patients undergoing knee or hip replacement surgery.

[Anticoagulants and dual antiplatelet therapy combined, a challenge to our intelligence]

The combination of antiplatelet and anticoagulant drugs, a common practice in the setting of acute coronary syndromes, constitutes an important practical problem involving difficult decisions, that lack support both in terms of clinical evidence (adequate clinical studies are not available) and strong guidelines. The problem was particularly aggravated from the moment when practically all the patients with acute coronary syndromes started to be submitted to double antiplatelet therapy, especially those treated with drug eluting stents. Simply reminding that 10% of these patients have or will have atrial fibrillation gives us the dimension of the problem. In this paper we discuss the benefits and risks of an eventual triple therapy and present the data obtained from the scarce evidence at our disposal, both from clinical studies and registries. The evidence about the combination of the double antiplatelet therapy with the new anticoagulants is derived from the phase II and phase III studies, conducted with dabigatran, apixaban, darexaban and rivaroxaban. The results from the only phase III study concluded with good results, the ATLAS-ACS 2 TIMI 51 study, conducted with rivaroxaban, are presented. The author also presents some of the recommendations extracted from the consensus document published on this matter by the Working Group on Thrombosis of the European Society of Cardiology.

Role of new anticoagulants for the prevention of venous thromboembolism after major orthopaedic surgery and in hospitalised acutely ill medical patients

Anticoagulation therapy for the prevention of venous thromboembolic events is indicated in patients after major orthopaedic surgery and in hospitalised acutely ill medical patients, who have a high or moderate risk of venous thromboembolism (VTE), respectively. Clinical trials have clearly demonstrated that short-term anticoagulation reduces the risk of VTE in these patient groups and that longer-term anticoagulation is beneficial for some indications. Evidence-based guidelines for thromboprophylaxis have been developed based on these studies. However, despite these guidelines, thromboprophylaxis is still underused, or used suboptimally, in many patients. This is, in part, because of the limitations of traditional anticoagulants such as unfractionated heparin, low- molecular-weight heparin, synthetic pentasaccharides, and vitamin K antagonists. Newer oral anticoagulants, such as rivaroxaban, apixaban, and dabigatran etexilate, have certain advantages over traditional agents. They can be administered orally at a fixed dose without routine coagulation monitoring and have minimal food and drug interactions. These characteristics may result in better adherence to guidelines and improved patient outcomes. This review provides an overview of phase III clinical trial data for these newer anticoagulants in major orthopaedic surgery and in hospitalised acutely ill medical patients, and discusses their potential for extended use in the post-hospital discharge setting. All three newer oral anticoagulants are approved in many countries for the prevention of VTE after hip replacement or knee replacement surgery in adult patients, and it is likely that these drugs will contribute considerably towards reducing the substantial healthcare burden associated with VTE.