Dabigatran efficacy-safety assessment for stroke prevention in patients with atrial fibrillation

Optimizing prognosis in atrial fibrillation: A call to action in Portugal

Atrial fibrillation (AF), the most common arrhythmia in the adult population worldwide, represents a significant burden in terms of cardiovascular mortality and morbidity and has repercussions on health economics. Oral anticoagulation (OAC) is key to stroke prevention in AF and, in recent years, results from landmark clinical trials of non-vitamin K oral anticoagulants (NOAC) have triggered a paradigm shift in thrombocardiology. Despite these advances, there is still a significant residual vascular risk associated with silent AF, bleeding, premature sudden death and heart failure. The authors review AF epidemiologic data, the importance of new tools for early AF detection, the current role of catheter ablation for rhythm control in AF, the state-of-the-art in periprocedural OAC, the optimal management of major bleeding, the causes of residual premature death and future strategies for improvements in AF prognosis.

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.

New oral anticoagulants in atrial fibrillation: a reappraisal of trial results looking at absolute figures

Three new oral anticoagulant agents were tested versus warfarin in separate, large phase III randomized clinical trials for prevention of any stroke and systemic embolism in atrial fibrillation. Dabigatran, a direct thrombin inhibitor, is at 110 mg bid non-inferior and at 150 mg bid superior to warfarin; rivaroxaban, a factor X inhibitor, is also non-inferior, and apixaban, also a factor X inhibitor, is superior to warfarin on the same efficacy end point. Statistical analysis of subgroups does not suggest, for any of the tested drugs, major differences in relation to different risk levels and history of previous stroke/TIA. This re-appraisal of data was undertaken in search for possible additional information, by considering the absolute differences in efficacy and safety events versus warfarin and the corresponding efficiency and number needed to treat, also with regard to secondary versus primary prevention. By this approach, it appears that for all drugs, equivalence or advantage versus warfarin on the efficacy end point is largely driven by a reduction in hemorrhagic rather than ischemic strokes. Dabigatran shows a balanced effect on ischemic and hemorrhagic strokes, and apixaban is most effective in sparing intracranial bleeding versus warfarin. In secondary prevention, better efficiency is shown by dabigatran 150 and apixaban, versus rivaroxaban, despite the higher proportion of post-stroke/TIA patients (55 %) in the ROCKET AF trial of rivaroxaban seemed to favor better results of this drug in secondary prevention. These and other results of our approach should not be directly translated into clinical practice. They may supply useful suggestions to be subsequently tested in specific trials, although head-to-head comparative studies of the three drugs remain unlikely.

Antithrombotic therapy for stroke prevention in non-valvular atrial fibrillation

The world faces an epidemic of atrial fibrillation and atrial fibrillation-related stroke. An individual's risk of atrial fibrillation-related stroke can be estimated with the CHADS(2) or CHA(2)DS(2)VASc scores, and reduced by two-thirds with effective anticoagulation. Vitamin K antagonists, such as warfarin, are underused and often poorly managed. The direct thrombin inhibitor dabigatran etexilate and factor Xa inhibitors rivaroxaban and apixaban are new oral anticoagulants that are at least as efficacious and safe as warfarin. Their advantages are predictable anticoagulant effects, low propensity for drug interactions, and lower rates of intracranial haemorrhage than with warfarin. A disadvantage is the continuing need to develop and validate rapidly effective antidotes for major bleeding and standardised tests that accurately measure plasma concentrations and anticoagulant effects, together with the disadvantage of possible higher rates of gastrointestinal haemorrhage and greater expense than with warfarin. The new oral anticoagulants should increase the number of patients with atrial fibrillation at risk of stroke who are optimally anticoagulated, and reduce the burden of atrial fibrillation-related stroke.

Acute management of bleeding in patients on novel oral anticoagulants

Novel oral anticoagulants that directly inhibit thrombin (dabigatran) or factor Xa (rivaroxaban, apixaban) are currently available for prevention of venous thromboembolism (VTE) after orthopaedic surgery, treatment of acute VTE, and prevention of arterial thromboembolism in non-valvular atrial fibrillation. These agents offer advantages over VKAs, including rapid onset, shorter half-lives, fewer drug interactions, and lack of need for routine monitoring. However, there are no established agents to reverse their anticoagulant effect. We review the risk of bleeding with the novel oral anticoagulants and the limitations of conventional coagulation assays for measuring anticoagulant effect. We provide an approach to the management of patients with bleeding complications with evidence for various interventions for reversal, where available.