New Anti-Clotting Agents as An Alternative to Warfarin?

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Recent research suggests that non-vitamin K antagonist oral anticoagulants (NOACs) are as effective as warfarin for treating atrial fibrillation in high-risk patients.

 

Atrial fibrillation (AF) is an irregular and rapid heart rate that can increase the risk of stroke, heart failure and other cardiovascular complications. The signs usually include dizziness, fatigue, and weakness. Treatment regimens for AF include surgical interventions such pacemakers, ablation and cardioversion (electric shocks). However, the first step is to address lifestyle and medication.Antiplatelet and anticoagulant agents work by preventing blood clot formation or by dissolving existing blood clots. Warfarin, sold under the brand name Coumadin, is a blood thinner used to treat blood clots and prevent stroke in people who have AF. It is on the WHO’s List of Essential Medicines, and one of the most effective and safe medicines in the health system.

Although it is a highly effective treatment in individuals with AF, warfarin anticoagulation can be difficult to manage and requires frequent monitoring. Another class of drugs called the non-vitamin K antagonist oral anticoagulants (NOACs) have been shown to be effective for the treatment of AF. A study led by Dr. Lip and colleagues used data from Danish registries to compare the safety and efficacy of the two drug classes. The work was published in JAMA Cardiology. The nationwide observational study included 14,020 (37% women) high-risk participants. The safety of NOACs (dabigatran at 150 mg twice daily, rivaroxaban at 20 mg once daily, and apixaban at 5 mg twice daily) was compared with standard warfarin treatment. Patients with prior health issues such as stroke, systemic embolism, ischemic attack, and cancer were excluded. The main outcomes and measures were rates of ischemic stroke/systemic embolism, death and bleeding.

The overall conclusion of the study was that there were no significant differences between NOACs and warfarin in patients at risk of stroke or embolism. It should be noted that the “any bleeding” outcome was lower for NOACs (apixaban and dabigatran) than for warfarin. The main limitation of this study was its observational nature, which tends to introduce confounding factors like diet, lifestyle, other ailments and medical treatments, and biases that can potentially change the outcome of the statistical analysis. The authors also noted that assessment of the full prescribing behaviour is required before a definitive conclusion can be drawn. Nonetheless, this study suggests that the safety and effectiveness of NOACs and warfarin fall in a similar realm of efficacy and warrants a randomised trial in a larger population.

 

Written By: Akshita Wason, B. Tech, PhD

 

Lip, Gregory YH, et al. “Effectiveness and Safety of Standard-Dose Nonvitamin K Antagonist Oral Anticoagulants and Warfarin Among Patients With Atrial Fibrillation With a Single Stroke Risk Factor: A Nationwide Cohort Study.” JAMA cardiology (2017).