Daily Archive 04.02.2019

Warfarin for Atrial Fibrillation

Warfarin, an antagonist of vitamin K, is well known in clinical practice, but it has significant drawbacks. To regulate the dose of the drug in order to maintain an internationally normalized ratio (MHO) at the therapeutic level (between 2.0 and 3.0), regular blood tests are required. In a significant proportion of patients, maintenance of anticoagulation at a therapeutic level cannot be achieved.

Many drugs affect the metabolism of warfarin and can lead to excessive anticoagulation (these include antibiotics, anticonvulsants, some statins, amiodarone, tamoxifen, and alcohol). The risk of bleeding may increase while taking aspirin. In connection with these shortcomings of the drug, doctors are often reluctant to prescribe warfarin, and patients in some cases refuse to take it.

Before surgery, it may be necessary to stop taking warfarin, which was prescribed to prevent systemic thromboembolic complications in patients with AF. In such cases, it is customary to prescribe heparin as a temporary bridge, but the use of heparin often creates the problem of bleeding and the formation of postoperative hematomas. In fact, the need for such a “heparin bridge” rarely arises: you can stop taking warfarin 3 days before the operation and resume 3 days after it.

More modern drugs. Recently, thrombin and factor Xa inhibitors have become available, which are prescribed in fixed dosages and therefore do not require regular blood tests to monitor their effectiveness. It has been shown that they are at least as effective as warfarin, and their use is associated with less or at least a similar risk of bleeding (especially intracranial hemorrhage), in addition, they interact to a lesser extent with other drugs. Nevertheless, although the results of clinical studies are promising, the experience of using these tools in clinical practice is still small.