Pradaxa Bleeding and Higher Heart Attack Risk?

Higher heart attack risk from Pradaxa, study shows: Here’s a note of caution for those who are taking blood thinners to manage atrial fibrillation or prevent stroke after a hip or knee replacement.

Patients taking the new anti-clotting drug Pradaxa have a higher risk—from 22 percent to 33 percent—of heart attack or severe symptoms of heart disease than do patients taking the older blood thinner, warfarin, a meta-analysis of various reports says.

That’s the range of relative increase in risk compared to other blood thinners—but the absolute risk increase for suffering a heart attack was only 0.27 percent, clarify the authors of the meta-analysis published online in the Archives of Internal Medicine Jan. 9 issue.

The findings, from Cleveland Clinic researchers Dr. Ken Uchino and Dr. Adrian V. Hernandez, is based on data from seven clinical trials that involved more than 39,500 patients and compared those on Pradaxa to others in control groups, who received either warfarin, Lovenox (enoxaparin) or a placebo. [

Pradaxa, known chemically as dabigatran, is approved in the United States for stroke prevention in patients suffering from an irregular heartbeat known as atrial fibrillation.

In Europe, Pradaxa is used to prevent strokes caused by blood clots in patients who have undergone hip and knee replacements. It’s also known as Pradaxa in Australia, but Pradax in Canada and Prazaxa in Japan.

The drug, produced by Germany’s Boehringer Ingelheim, has been touted as an alternative to warfarin, the blood thinner that has been used effectively for many decades, but which doctors say is hard to use.

Pradaxa was expected to compete with two other new blood clot and stroke preventers—Xarelto (rivaroxaban) from Bayer AG and Johnson & Johnson, and Eliquis (apixaban) from Bristol-Myers Squibb Co and Pfizer Inc. Approved by health regulators only in recent years, use of these three new anticoagulants was expected to rise in recent months, generating billions of dollars in sales.

Since October 2010, when it was approved by the U.S. Food and Drug Authority’s, until August 2011, doctors wrote about 1.1 million Pradaxa prescriptions and about 371,000 patients received Pradaxa prescriptions from U.S. outpatient retail pharmacies, Forbes reports.

Only a small increased risk of heart attack was linked to the use of Pradaxa compared to warfarin in the original study Boehringer used to gain the health regulator’s approval. At the same time, the study found that the drug slashed the risk of strokes by 35 percent.

But the new meta-analysis by the Cleveland Clinic researchers shows that Pradaxa boosts the risk of a heart attack and acute coronary syndrome (ACS), the umbrella term covering conditions of angina and chest pain typically caused by a blocked coronary artery.

Uchino, the study’s lead researcher and a neurologist, clarified that the actual increase in the number of heart attacks and ACS events was very small and is outweighed by the benefits—mainly, the drug’s ability to reduce the number of strokes.

“The overall benefit and risk balance of dabigatran use appears to be favorable in patients with atrial fibrillation because of reduction in ischemic stroke,” the study authors wrote. However, they caution, “clinicians should consider the potential of these serious harmful cardiovascular effects with use of dabigatran.”

The meta-analysis also found that these events occurred in 1.19 percent of Pradaxa patients and in 0.79 percent of control-group patients. The rate of death was also found to be lower for patients who received Pradaxa than those who got other medicines in clinical trials—4.83 percent versus 5.02 percent in control groups.

Dr. Uchino’s team called for more study of the drug’s potential to increase heart-attack risk.

In an editorial accompanying the study Archives of Internal Medicine, journal editor Dr. Rita Redberg notes that this isn’t the first safety warning issued for Pradaxa.