The threat of irreversible traumatic bleeding in Pradaxa (dabigatran) patients is proving to be a major disadvantage. Initially, the convenience of minimal monitoring seemed appealing to patients who are used to dealing with the older Coumadin (warfarin), but the fact that the bleeding cannot effectively be stopped is a serious deterrence. Earlier this month, the Journal of Neurosurgery reported the death of an elderly Pradaxa patient, who suffered from a brain hemorrhage following a minor fall, further demonstrating the dangerous lack of a reversal agent for Pradaxa.
Pradaxa is a direct thrombin inhibitor, a class of drugs that work by binding directly to thrombin, the central factor necessary for clotting. The U.S. Food and Drug Administration (FDA) approved the drug in October 2010 to prevent blood clots and stroke in patients with atrial fibrillation. Unlike Coumadin (warfarin), an older class of oral anticoagulant, Pradaxa does not require frequent monitoring or have a significant amount of food and drug interaction. According to the RE-LY trials in 2009, Pradaxa and Coumadin have similar bleeding risks, but Pradaxa seemed to demonstrate a lower annual incidence of stroke. However, the fact that there is no effect antidote to stop the bleeding with Pradaxa patients remains a serious concern.
According to a case report in the Journal of Neurosurgery, an 83-year old man died of a brain hemorrhage after a minor ground-level fall in his home. He had been taking a 150mg dose of Pradaxa twice a day for about one month to treat new-onset atrial fibrillation. After the fall, the man was treated at the University of Utah, where he initially appeared to be fully functional, said the doctors. A CT scan showed localized, superficial hemorrhaging which ended up encompassing most of the left brain after six hours. After unsuccessful treatment with recombinant factor VII, the man fell into a deep coma and died shortly afterward.
Typically, Pradaxa has a 12-hour half life. Due to its dependency on renal filtering, however, it tends to remain longer in elderly patients. Being a direct thrombin inhibitor, Pradaxa’s mechanism is activated at the end of a long chain of enzymatic reactions. Therefore, attempts to circumvent its action with clotting factors such as recombinant factor VII, are not effective. Dialysis is therefore the only way to remove the drug from the system. Researchers estimate that within two to three hours, 35 to 60 percent of Pradaxa can be removed through dialysis.
Unfortunately, by the time doctors considered dialysis, “it was too late to implement effectively” according to Fox News. This occurrence echoes the concern of a group of New Zealand hematologists, who published a study in the New England Journal of Medicine last month. The researchers had pointed out that the hemorrhaging is largely affected by patient’s kidney health, and emphasized the lack of a reversal agent. The group urged for better education about the issue among medical professionals; based on the recent developments, it is clear that familiarity with the bleeding risks and prompt treatment methods are essential to treating Pradaxa patients.