Another New Blood Thinner Linked to Increased Risk of Internal Bleeding

Merck & Co. is proposing another new generation blood thinner, similar to Pradaxa, which appears to also pose an increased risk of serious and potentially life-threatening bleeding events. 

According to results of a clinical trial presented this weekend at a meeting of the American College of Cardiology in Chicago, the proposed blood thinner Vorapaxar does appear to reduce the risk of dying from a heart attack or stroke by about 20% among individuals who have suffered a prior heart attack, but it nearly doubled the risk of internal bleeding.

The phase III trial tested Vorapaxar with standard therapy and compared the results to patients given a placebo. Part of the study was halted after patients with a history of stroke began suffering higher rates of brain hemorrhaging.

Merck is attempting to release the drug as the latest in a new generation of blood thinners, known as “direct thrombin inhibitors”, which inhibit the enzyme in the blood that causes blood to clot. Other approved mediations in the same class include Boehringer Ingelheim’s Pradaxa and Johnson & Johnson’s Xarelto.

The new blood thinners are supposed to be easier to use than Coumadin (warfarin), as they require less monitoring. However, concerns have grown in recent months about the risk of bleeding events, which can not be reversed when they occur.

While users of warfarin who suffer internal bleeding can be treated with Vitamin K to counter the blood thinning effects, Pradaxa and the other newer blood thinners in the same class do not have a quick fix, often referred to as a reversal agent.

Since Pradaxa (dabigatran) was introduced in October 2010, as the first member of this class, the medication has been linked to hundreds of deaths caused by internal bleeding and the FDA is currently investigating the safety of the medication.

According to a report released by the Institute for Safe Medication Practices in January 2012, more instances of internal bleeding with Pradaxa were reported to the FDA’s Adverse Event Reporting System during the first quarter of 2011 than were reported in association with any other drug monitored by the group.  At least 505 instances involving Pradaxa bleeding events were reported, compared to 176 cases reported with warfarin/Coumadin, which was second on the list.

A number of individuals throughout the United States are now considering a Pradaxa lawsuit against the drug maker for failing to adequately research the medication or warning about the risk of serious and potentially life-threatening health risks of Pradaxa.

The Vorapaxar study results were considered disappointing, and Merck officials have said they will take more time to consider what to do about the drug. However, the latest trial did show better results than a previous study, which found no health benefits from use of the drug.

Earlier this month, another proposed drug that is part of the same class of medications, which would be marketed as Eliquis, was dealt a set back when the FDA indicated that it was delaying a decision on the drug at least three months. There has been speculation that concerns over the risk of internal bleeding found with Pradaxa may have contributed to the FDA’s decision to delay their review.

However, another study presented at the same conference indicated that Johnson & Johnson’s Xarelto (rivaroxaban), which was the second member of this class of anticoagulants approved in the United States, was effective at preventing pulmmonary embolism and actually cut the risk of severe internal bleeding when compared to standard treatments, which involves the use of the injected drug enoxaparin, followed by use of warfarin to prevent the condition from occurring again.

That study comes as Johnson & Johnson begins to push for expanded use of Xarelto for prevention of blood clots that cause deep vein thrombosis (DVT) and pulmonary embolism. Researchers indicated that complicated two-drug standard treatment regimens could be replaced by Xarelto, and may actually lower the risk of severe hemorrhage associated with the current standard of care.