Concerns about the use of Pradaxa for stroke prevention

New reports are raising concerns about Pradaxa, because of serious and sometimes fatal bleeding associated with the drug.  

A recent analysis found Pradaxa was “significantly associated with a higher risk” of heart attacks and acute coronary syndrome (ACS). The study concluded that “the overall benefit and risk balance of dabigatran use appears to be favorable in patients with AF because of reduction in ischemic stroke. However, the cardiac risk of dabigatran should be investigated further, especially if it is used in populations at high risk of MI or ACS.”

Pradaxa has recently been approved for preventing stroke in patients with Atrial fibrillation (AF). AF accounts for approximately 15% of all strokes. Other factors such as hypertension, diabetes mellitus, congestive heart failure and prior stroke, all increase the risk of stroke in AF as well.

Blood thinners stop blood from clotting, which may cause strokes. Currently, warfarin (Coumadin) and now also dabigatran (Pradaxa) are approved therapies for stroke prevention in patients with AF. While Coumadin is effective, it has a “narrow therapeutic window,” sometimes delivering too much or too little of its blood-thinning effect. It requires frequent monitoring and dose adjustments. It also reacts with some foods and many other medications.

In comparison of pradaxa with coumadin, both will reduce the risk of a stroke by about the same margin, but pradaxa increased the risk of heart attacks by about 0.4% and gastrointestinal bleeding by 0.6%. Pradaxa is also about 10 times more expensive than coumadin.

Coumadin requires regular monitoring and dose adjustments. Dabigatran was created to provide an alternative to Coumadin, with as specific advantage that the frequent blood checks (as with Coumadin) are not necessary.

Pradaxa has a rapid onset of action, with very few drug-drug interactions and patients don't require any form of monitoring. However, one of the major drawbacks of Pradaxa is that, unlike Coumadin, there is no easy way to reverse the effects of the blood thinning, an issue that may be important to control other causes of bleeding.

A recent report from Quarterwatch, which analyzes adverse drug reaction reports in the US, noted that, after dabigatran (Pradax) was approved in the US (in October 2010), it “moved to near the top of our adverse event rankings, with more reports than 98.7% of the drugs we regularly monitor.” The Quarterwatch analysis found the problems mostly centered on the drug’s clotting mechanism, finding both excessive bleeding (not enough clotting) and not enough effect, including thromboembolic events such as pulmonary embolism and deep vein thrombosis.


1. Dabigatran Association With Higher Risk of Acute Coronary Events, Ken Uchino, MD; Adrian V. Hernandez, MD, PhD, Arch Intern Med. Published online January 9, 2012.

2. QuarterWatch: 2010 Quarter 4 Monitoring; MedWatch Reports October 6, 2011