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Federal drug regulators have received a surprising number of reports involving blood clots associated with the new anticoagulant Xarelto, which is in contrast to the bleeding problems seen with Pradaxa, which is another new blood thinner in the same class of medications.
Xarelto (rivaroxaban) was introduced by Johnson & Johnson’s Janssen Pharmaceuticals in July 2011, as the second medication from a new class of blood thinners known as a direct thrombin inhibitor. The class is promoted as a superior alternative to warfarin for prevention of blood clots in certain cases, as they require less monitoring.
The first medication approved from this class in the United States was Pradaxa (dabigatran), which was introduced in October 2010. However, since it was introduced, side effects of Pradaxa have been linked to a shocking number of severe bleeding events, hemorrhages and deaths, particularly among older patients with atrial fibrillation.
Over the past two years, Pradaxa has quickly become one of the medications most-commonly associated with adverse events reported to the FDA.
Report Shows “Unexpected” Rate of Xarelto Blood Clot Reports
Earlier this month, the Institute for Safe Medication Practices (ISMP) released their QuarterWatch report (PDF), which analyzed adverse events submitted to the FDA over the first quarter of 2012.
The report highlighted adverse events involving Xarelto problems, which accounted for at least 356 adverse event reports submitted to the agency during the first quarter of 2012. This represented nearly double the number of reports submitted to the agency in connection with the new drug when compared to the last quarter of 2011.
Unlike Pradaxa, the most common problem with Xarelto was not bleeding, but rather severe blood clots, particularly among younger patients under the age of 66, who were taking the anticoagulant after hip or knee surgery. According to the report, the agency received at least 158 reports involving Xarelto blood clots during the first quarter.
“The unexpected result was that unlike other anticoagulants…the primary reported event was not the well-understood risk of hemorrhage,” the report states. “Instead, the largest identifiable category was serious blood-clot-related injury – most frequently pulmonary embolism – the very events [Xarelto] is intended to prevent.”
Janssen Pharmaceuticals, a subsidiary of Johnson & Johnson, told ISMP that the number of blood clot reports were simply a sign of how well the drug was doing. The company suggested that it could not be compared directly with Pradaxa because it was used on different populations for different problems for different durations.
While both blood thinners are new drugs aimed at replacing Coumadin (warfarin), which has been on the market since the 1950s, they have very different population profiles. Xarelto targets a younger population than Pradaxa, and is approved by the FDA to prevent venous and pulmonary embolism in patients who are undergoing knee replacement surgery or hip replacement surgery.
The ISMP warned that the blood clot and pulmonary embolism reports, some of which included fatal injuries, could be a sign of “sub-therapeutic doses or some other form of unexpected lack of efficacy,” and said that the problem should be further investigated.
Concerns Over Bleeding Side Effects of Pradaxa and Xarelto
Xarelto and Pradaxa both work by affecting the enzyme in the blood that causes blood to clot. The drugs have been promoted as superior to warfarin, the go-to-anticoagulant for decades, because they require less monitoring during treatment.
However, when severe bleeding problems develop with warfarin, reversal agents are available to stop the blood thinning effects of the older drug, while such quick antidotes are not readily available with the new line of drugs.
Although Xarelto was associated with about 121 reports of hemorrhages during the first quarter of 2012, representing about 34% of all adverse events associated with the medication, the number paled in comparison to Pradaxa, which was associated with more than 600 reports of bleeds, which was more than three times the number of adverse events reported involving blood clots with Pradaxa.
Hundreds of individuals throughout the United States are now pursuing a failure to warn lawsuit over Pradaxa, alleging that Boehringer Ingelheim, the maker of Pradaxa, failed to adequately warn about the bleeding risk or lack of a reversal agent.
The federal Pradaxa litigation has been consolidated for pretrial proceedings in the U.S. District Court for the Southern District of Illinois, where the cases have been centralized before U.S. District Judge David R. Herndon. According to a case management order issued earlier this month, the first Pradaxa trials are expected to begin in August 2014.
Expanded Use of Xarelto Being Pursued
The makers of Xarelto have been pushing for expanded approval of the new blood thinner for prevention of heart attacks and strokes among certain patients, but the FDA has previously denied approval amid concerns about the reported bleeding events associated with Pradaxa.
At the time the original application to extend approval for Xarelto was denied, the FDA also raised concerns about missing data from a clinical trial, after about 1,300 patients dropped out of the 15,526-subject trial during its final phase. There was inadequate information about why the numbers dropped, and the participants withdrew consent to access their health records.
Last month, additional information was submitted to the FDA by Johnson & Johnson and Bayer, in an attempt to overcome concerns over the risk of bleeding problems associated with the new class of anti-coagulants and obtained expanded approval for the medication.