Dabigatran, marketed as Pradaxa in the U.S., belongs to a class of medications called the direct thrombin inhibitors. It is FDA approved for reducing the risk of stroke and blood clots in patients with atrial fibrillation (a heart rhythm abnormality) not caused by a heart valve problem. This class of medications is involved in blocking a central clotting agent, called thrombin which binds blood to form clots. Warfarin, also known as Coumadin, is a much older blood thinner that inhibits vitamin K and, therefore, the production of important clotting factors. Like warfarin, Pradaxa is available as an oral pill. It is supplied as 75 mg and 150 mg capsules.
What are the advantages of Pradaxa over warfarin?
Pradaxa does not require routine blood level tests like the International Normalized Ratio (INR). Therefore unlike warfarin, patients taking Pradaxa do not require routine visits to an anticoagulation clinic.
Pradaxa is not affected by vitamin K. Therefore, there are no dietary restrictions involving vitamin K rich foods such as green leafy vegetables.
Unlike warfarin, Pradaxa is not metabolized by the common liver enzymes responsible for metabolizing many drugs, so there are fewer drug interactions.
Titration is not required when dosing Pradaxa.
How does the efficacy and safety of Pradaxa compare to warfarin?
In a multi-national, randomized trial called the RE-LY (Randomized Evaluation of Long-term Anticoagulant Therapy) Trial consisting of over 18,000 people, only 1.11% of patients on Pradaxa 150 mg was associated with stroke and blood clots compared to 1.69% of patients on warfarin. That is about 34% fewer strokes or blood clots when compared to warfarin.
Based on the results of the RE-LY Trial, Pradaxa (0.74%) did have a higher rate of heart attacks than warfarin (0.53%) per year. That is about a 40 percent increase of events in Pradaxa from warfarin.
The RE-LY Trial also showed that Pradaxa (3.11%) had similar bleeding risks to warfarin (3.36%) per year.
In November 2012, the FDA published a re-evaluation on the bleeding risks of dabigatran and warfarin in response to newer post-marketing reports. They did a retrospective analysis using health insurance claims and data to observe the rates of abnormal bleeding events for Pradaxa and warfarin. The results were consistent with the RE-LY study. Pradaxa did not display more bleeding than warfarin.
What are the disadvantages of Pradaxa over warfarin?
Pradaxa is taken twice daily while warfarin is taken once daily.
Pradaxa is much more sensitive to the atmosphere when exposed and should be used within 4 months after the manufacturer’s container is opened.
The dosing of Pradaxa must be reduced to 75 mg twice daily or avoided in patients with poor kidney function (CrCl < 30 mL/min). Warfarin does not require dosing adjustments for poor kidney function.
There are no antidotes that can reverse the effects of Pradaxa.
An annual spending on Pradaxa may cause thousands of dollars because there is no generic equivalent available. This is much more than warfarin, which is available as a generic and cost a few hundred dollars at most annually.