New anticoagulant drug and head injury: Do not mix

Dabigatran (marketed as Pradaxa) is a new drug used by a growing number of Americans with atrial fibrillation. It’s both easier to take and more effective at reducing the risk of stroke than warfarin, a drug that’s been in use since the 1950s. But a case report published this week underscores a danger with the new medication: If a patient taking it is bleeding into the brain or elsewhere, there is currently no fast, effective way to reverse the blood-thinning agent’s effects.

For one 83-year-old man who was taken to the University of Utah Hospital’s emergency department after falling and hitting his head, the result was death.

The publication of the case study in the Journal of Neurosurgery comes as the U.S. Food and Drug Administration continues to study reports of “serious bleeding events” in patients taking Pradaxa. The agency is trying to determine whether those medical crises were related to the drug, and whether the risk of such bleeding events is higher than would be expected.

Some risk of excessive bleeding is anticipated with anticoagulants such as Pradaxa and warfarin, because that is how they reduce stroke risk. In atrial fibrillation, stroke-inducing blood clots are more likely to form in recesses where blood pools close to the heart. Thinning a patient’s blood prevents such clots from forming, but doing so also makes wounds, lacerations and internal bleeding slow to stop.

The patient described in the case study had been taking a high dose of Pradaxa for just a month after he was diagnosed with atrial fibrillation, a condition that affects about 2 million Americans. He had suffered a “ground-level fall” and was found to have some bleeding in his brain. A check of his blood showed that the drug had been effective in slowing clot formation, and raised the specter that the man’s brain-bleed would be difficult to stop. In two hours, he began to have difficulties speaking, and the bleeding in his brain had spread widely. He died slightly over six hours after he arrived at the hospital.

Even without blood thinners, people who fall and hit their head can die of a brain bleed, as the death of actress Natasha Richardson made clear. But if a medication makes that more likely, physicians like to know how they can neutralize that effect quickly.

“There is currently no effective antidote to reverse the anticoagulant effect of dabigatran in the event of an emergency,” the authors of the case study noted. Kidney dialysis might have removed as much as 60% of the drug from the patient’s body in two to three hours, the authors said. But the patient’s bleeding outran the physicians’ efforts to control it.

For patients taking warfarin, physicians have a ready way to restore the blood’s ability to coagulate: They can give the patient vitamin K, fresh-frozen plasma or coagulation factors that warfarin has suppressed.

Between the time Pradaxa came on to the U.S. market in late 2010 and August 2011, the FDA says that 371,000 patients in the United States began taking the drug -- many of them switching from warfarin. By the end of June 2011, the FDA had received 1,583 reports of “gastrointestinal hemorrhages” and 466 cases of “vascular hemorrhagic” complaints.

“Neurosurgeons are likely to encounter this scenario more frequently with the increased use of dabigatran and other similar drugs,” the authors of the study wrote. Early efforts to develop a quick antidote have so far failed, they reported, so “new treatments are certainly needed.”