A Promising Drug With a Fatal Flaw

Just two years after its approval by the FDA, a dangerous flaw in the new drug Pradaxa has come to light. Pradaxa is an anti-clotting drug prescribed to patients with artial fibrillation.

When the F.D.A. approved Pradaxa in October 2010, the drug was hailed as the first in a new category of replacements for warfarin, the nearly 60-year-old drug used to prevent strokes in people with a heart-rhythm disorder known as atrial fibrillation. Pradaxa has become a blockbuster drug in its two years on the market, bringing in more than $1 billion in sales for its maker, the privately held German drug maker Boehringer Ingelheim. About 725,000 patients in the United States have used the drug, according to the F.D.A.

Warfarin requires careful monitoring of a patient’s diet and drug regimen, and frequent blood tests to ensure that it is working. Pradaxa required no such monitoring and, compared with warfarin, appeared to be better at preventing strokes.

Unlike warfarin, there is no antidote to reverse the blood-thinning effects of Pradaxa. Warfarin, which is also known by the brand name Coumadin, can often be reversed by giving a patient vitamin K or other substances. Warfarin, too, can be deadly but, doctors said, they at least have options.

The risk with Predaxa is that if a patient starts bleeding, doctors will be unable to stop the bleeding. “The practical experience is that once hemorrhagic complications occur in this drug, it is much more likely to be a catastrophe than with Coumadin,” said Dr. Richard H. Schmidt, an associate professor of neurosurgery at the University of Utah, who treated an 83-year-old man who died from bleeding and was using Pradaxa.

Pradaxa was identified as the primary suspect in 542 patient deaths reported to the F.D.A. in 2011, and was linked to more reports of injury or death than any of the more than 800 drugs regularly monitored by the Institute for Safe Medication Practices, a nonprofit based in Pennsylvania that monitors medicine safety. Some reports have indicated that doctors are not sufficiently cautious when prescribing Pradaxa, giving the drug to older people or those with kidney problems even though there is evidence that the bleeding risks are higher in those groups. Boehringer Ingelheim recommends testing patients’ kidney function before prescribing Pradaxa and notes that the risk of bleeding increases with age.

A chorus of complaints has risen from doctors, victims’ families and others in the medical community, who worry that the approval process was not sufficiently rigorous because it allowed a potentially dangerous drug to be sold without an option for reversing its effects. Pradaxa is an example, some critics say, of what can happen when a drug that performs well in tightly controlled trials is released into the messy world of real-life medicine.

The Food and Drug Administration released a report on Friday that found that the drug did not show a higher risk of bleeding than for patients taking warfarin. The report did not address the lack of an antidote for Pradaxa.

More than 100 lawsuits have been filed in federal courts related to Predaxa, and thousands more are expected.