Abstract
Warfarin has a long history of benefit and has become the gold standard medication for the prevention of ischemic stroke in patients with atrial fibrillation. Nevertheless, it is far from perfect and there is no doubt that new drugs must be found to replace warfarin. The new oral anticoagulants that are on the market or awaiting approval or under research offer some benefits but not enough to replace warfarin until results of additional studies can show an adequate balance between effectiveness/safety and cost/benefit. There are several issues concerning the new oral anticoagulants. It is essential that the effect of any anticoagulant can be measured in plasma. But to date, there is no test to assess the effect or therapeutic range for the new oral anticoagulants. There is no antidote to neutralize the action of the new drugs in cases of bleeding or when acute surgical intervention is necessary. Dabigatran requires dose adjustment in patients with moderate renal impairment and is contraindicated in patients with severe renal failure. Rivaroxaban should be used with caution in patients with severe renal impairment. Apixaban excretion is also partly dependent on renal function, although the impact of renal insufficiency has not yet been determined. How anticoagulant bridging can be done before surgery has not yet been established. In conclusion, although thousands of patients have been treated in phase III studies, additional data are necessary before conclusions can be drawn on the potential for these new anticoagulant drugs to replace warfarin in patients with atrial fibrillation.
Highlights
Atrial fibrillation (AF) is the most common arrhythmia
The study results showed that rivaroxaban significantly reduced intracranial bleeding compared with warfarin
There is no doubt that new drugs must be found to replace warfarin
Summary
Atrial fibrillation (AF) is the most common arrhythmia. AF can present with significant symptoms or with just a few cardiodynamic modifications that the patient is not aware of. It is essential that the effect of any anticoagulant medication can be measured in plasma, as done by prothrombin time for warfarin control, activated partial prothrombin time for administration of regular unfractionated heparin or the assay for plasma levels of antiactivated factor X in the case of low molecular weight heparins to avoid excessive or deficient anticoagulation predisposing to hemorrhagic or thrombotic accidents. Among the potential new therapies a warfarin-related drug, tecarfarin [5], a vitamin K antagonist similar to warfarin, has been studied It is a vitamin K epoxide reductase inhibitor which decreases the activity of vitamin K-dependent coagulation factors (factors II, VII, IX, and X) and prolongs the prothrombin time [6]. The first study was published in Circulation 2 years ago [7] on a group of 66 patients, and more trials can be expected to identify further benefits compared with warfarin and other oral anticoagulants. Having a specific antidote and a more stable action compared with warfarin gives tecarfarin an interesting profile for the prevention of thromboembolic diseases
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