Will Warfarin Soon Be Passé? New Approaches to Stroke Prevention in Atrial Fibrillation

Dabigatran etexilate: a review of its use in the prevention of stroke and systemic embolism in patients with atrial fibrillation

The need for safe, effective, and easily administered and monitored antithrombotic treatments that do not have the issues common to warfarin treatment has led to the development of new anticoagulant drugs. Dabigatran etexilate (Pradaxa®, Pradax™) is a prodrug of the direct thrombin inhibitor dabigatran, a direct, reversible, potent inhibitor of thrombin. Dabigatran does not interact with food, and is associated with very few known drug interactions. Dabigatran etexilate, at dosages of 110 and 150 mg twice daily, was shown to be noninferior to warfarin with regard to the incidence of stroke or systemic embolism in a large, randomized, partially blinded, multicenter study in a wide spectrum of patients with atrial fibrillation. Moreover, the higher dosage was associated with significantly greater efficacy than warfarin in this regard. These results were supported by secondary endpoints and subgroup analyses. In general, dabigatran etexilate is well tolerated, although it is associated with a higher rate of dyspepsia than warfarin. Major bleeding was as common in recipients of the higher dosage as, and less common in recipients of the lower dosage of dabigatran etexilate than, that in recipients of warfarin, and intracranial bleeding, life-threatening major bleeding, and total bleeding were less common in recipients of either dabigatran etexilate dosage than in warfarin recipients. However, the higher dosage of dabigatran etexilate was associated with a higher rate of gastrointestinal bleeding than warfarin. The incidence of hepatotoxicity did not significantly differ across treatment groups. In conclusion, dabigatran etexilate 150 mg twice daily is more effective than warfarin for the prevention of stroke and systemic embolism in patients with atrial fibrillation, and generally well tolerated, particularly with regard to bleeding endpoints compared with warfarin. It requires more frequent administration than warfarin, but provides multiple improvements to various issues associated with warfarin administration. Direct comparisons with other new anticoagulant drugs would be beneficial, as would further investigation into the effects in different patient populations, long-term effects, and the gastrointestinal bleeding and dyspepsia observed with dabigatran etexilate treatment. Dabigatran etexilate is a promising new option for the prevention of stroke and systemic embolism in patients with atrial fibrillation.

Phenyltriazolinones as potent factor Xa inhibitors

We have discovered that phenyltriazolinone is a novel and potent P1 moiety for coagulation factor Xa. X-ray structures of the inhibitors with a phenyltriazolinone in the P1 position revealed that the side chain of Asp189 has reoriented resulting in a novel S1 binding pocket which is larger in size to accommodate the phenyltriazolinone P1 substrate.

Stroke prevention versus bleeding risk of vitamin-K antagonists: a double-edged sword in patients with atrial fibrillation who require surgery

Patients with atrial fibrillation taking vitamin-K antagonists and undergoing invasive interventions or large surgery procedures are at highest risk of bleeding complications. Therefore, the temporary interruption of vitamin-K antagonists and bridging with heparin is a frequent clinical need, particularly in patients with high risk for stroke. The management of such patients is challenging because of the lack of randomized clinical trials assessing different periprocedural anticoagulation approaches and inconsistent recommendations from consensus groups. Recent non-randomized trials have helped to estimate the risks of thromboembolism and bleeding with "bridging" anticoagulation involving either low-molecular-weight heparin or intravenous unfractioned heparin. Nevertheless, there is still a clear need for randomized double-blinded controlled trials comparing efficacy and safety of the different "bridging" strategies, including unfractionated heparin and placebo comparators, in preventing thromboembolism for specific patients and procedures.