WEDNESDAY, Dec. 22 (HealthDay News) -- A new drug, apixaban, may be better for preventing dangerous blood clots in the legs and lungs after hip replacement surgery than a commonly used older drug, a new study finds.

Researchers in Denmark compared the two anti-clotting drugs in a head-to-head test involving about 5,400 hip replacement patients.

About 3.9 percent of patients given the older drug, enoxaparin, developed venous thromboembolism (clot in the legs), a pulmonary embolism (clot in the lungs) or died after the surgery, according to the study.

That compares to only 1.4 percent of patients given apixaban.

Apixaban is being developed by Bristol-Myers Squibb and Pfizer, which funded the Phase III trial reported in the Dec. 23 issue of the New England Journal of Medicine.

The company has applied to the U.S. Food and Drug Administration for drug approval and expects to complete the application process in the first quarter of 2011, said Christina Trank, associate director of public affairs for Bristol-Myers Squibb, headquartered in New York City.

Sanofi-Aventis makes the older drug, enoxaparin (Lovenox).

"The apixaban was superior to enoxaparin, including the total number of patients with thromboembolism and major embolism," said lead study author Dr. Michael Rud Lassen, a spine surgeon and clinical researcher at Horsholm Hospital at the University of Copenhagen.

Deep vein thrombosis is one of the most common complications after lower extremity surgery, including hip and knee replacement, explained Dr. Richard Stein, a professor of cardiology at New York University School of Medicine and a spokesman for the American Heart Association.

Clots can form in the veins of the legs, leading to chronic swelling, and a piece of the clot can break off and travel to the lungs, forming a pulmonary embolism, which can be fatal.

After hip replacement, patients typically receive (warfarin) Coumadin, a blood thinner that inhibits clotting. But Coumadin takes a day or more to kick in, so patients usually are immediately put on enoxaparin, Stein added.

There are several drawbacks to that strategy. Enoxaparin is delivered by injection, whereas apixaban can be taken in oral form.

Coumadin can be somewhat unpredictable and patients taking it have to be monitored, Stein said.

"It often is difficult to find the right dosage. Sometimes we overshoot and patients are at risk of bleeding, and sometimes we undershoot and they are at risk of getting the clot in their vein," Stein said.

The new drug seemed to reduce clots by nearly half and resulted in slightly fewer problems with bleeding at the surgical site, Stein said.

"This is an important article," Stein said. "They showed a reduction in bleeding and a reduction in major and minor complications, including deep vein thrombosis, non-fatal pulmonary embolism or cardiac death, which usually means fatal pulmonary embolism. They showed those risks were reduced substantially in the group taking the apixaban compared to the enoxaparin group."

Apixaban is also being studied for use after knee replacement surgery and for patients with atrial fibrillation, among other conditions. In addition to the hip replacement study, there are eight other completed or ongoing Phase III clinical trials involving the drug, Trank said.

Apixaban is one of several drugs under development that work by inhibiting factor Xa in the blood, according to an accompanying editorial that predicts a huge impact if the drug is "conscientiously priced."

Bristol-Myers Squibb declined to provide information about the cost of the drug.

More information

The U.S. National Heart, Lung, and Blood Institute has more on deep vein thrombosis.