SUNDAY, July 24 (HealthDay News) -- For patients suffering chest pain, adding a new anti-clotting drug, Eliquis, to dual antiplatelet therapy may result in severe bleeding without reducing the risk of heart attack and stroke, a new study finds.

A trial evaluating the combination treatment was halted early when the risk of severe bleeding among those taking Eliquis (apixaban) became apparent.

"It is very clear there is an increased risk of bleeding, and in most patients it doesn't appear there is a lot of benefit to outweigh the risk of bleeding," said researcher Dr. John H. Alexander, co-director of cardiovascular research at the Duke Clinical Research Institute of Duke University Medical Center in Durham, N.C.

"We know high-risk patients with acute coronary syndromes continue to have events, and we know antiplatelet therapy is effective," said Alexander. The researchers expected to see some increase in bleeding when they added Eliquis to other anti-clotting therapy, but the bleeding was significant and "there was nothing to offset that increase in bleeding, so we stopped the trial," he said.

The conclusion: "Combination treatment with an anticoagulant and dual antiplatelet therapy should be avoided unless there is a clear indication for both, as in some patients with atrial fibrillation," Alexander said.

The report was published online July 24 in the New England Journal of Medicine to coincide with presentation of the study results at the International Society on Thrombosis and Haemostasis Congress, July 23-28 in Kyoto, Japan.

For the study, researchers randomly assigned 7,392 patients who were receiving standard antiplatelet therapy with two drugs to an additional 5 milligrams of Eliquis or a dummy pill twice daily. The study was double-blind, meaning that neither the patients nor the researchers knew who was taking Eliquis or a dummy pill.

Eliquis is a so-called Xa inhibitor, which is a class of anticoagulants that work by blocking factor X, a protein involved in blood clotting.

Over an average follow-up of eight months, 7.5 percent of the patients receiving Eliquis had a heart attack, suffered a stroke, or died, as did 7.9 percent of the patients receiving placebo, the researchers found.

In addition, 1.3 percent of those taking Eliquis had major bleeding, compared with 0.5 percent of those receiving the placebo, they noted.

Moreover, more patients taking Eliquis had bleeding into the brain and died from uncontrollable bleeding than patients receiving placebo, Alexander said.

Would a lower dose of Eliquis work? Alexander is skeptical. While it could reduce the risk of bleeding, he said he doubts more heart attacks, strokes or deaths would be prevented.

The trial was funded by Pfizer/Bristol-Myers Squibb, the makers of Eliquis.

Commenting on the study, Dr. Gregg C. Fonarow, a professor of cardiology at the University of California, Los Angeles, said that "each year more than 1.4 million men and women are admitted to hospitals in the United States with acute coronary syndromes."

Despite conventional therapy, patients with acute coronary syndromes remain at risk for recurrent cardiovascular events, Fonarow said.

A number of medications that prevent blood clots (known as antithrombotic drugs) "are being evaluated in patients with acute coronary syndromes to determine if they can further reduce cardiovascular event risk without substantially increasing the bleeding risk when added to conventional therapies," he said.

Apixaban and two other drugs, rivaroxaban (Xarelto) and dabigatran (Pradaxa), have been shown to provide significant benefit in reducing stroke and clots in patients with atrial fibrillation, where the benefit outweighs the bleeding risk, Fonarow said.

"However, this new study suggests that the use of apixaban, at least at the dose studied, should be avoided in patients with recent acute coronary syndromes being treated with dual antiplatelet therapy," he said.

More information

For more information on heart disease, visit the U.S. Centers for Disease Control and Prevention.