Originally created 03/01/01

New drug dramatically cuts risks of blood clots after hip replacement



A new synthetic drug dramatically cuts the risk of blood clots after surgery and could one day replace a blood thinner that has been used for decades, researchers say.

Blood clots in the leg, a condition called deep-vein thrombosis, are a common complication of major operations such as hip replacement. The clots can be deadly if they break off and travel through the bloodstream to the lungs.

Researchers found that the experimental drug reduced the risk of clots by as much as 82 percent after hip replacement when compared with the standard treatment, a refined version of the blood thinner heparin.

The new drug, known as a synthetic pentasaccharide, targets the key clotting protein in the blood and prevents it from clumping. The study was designed primarily to determine the proper dose for further tests, but it also showed the drug to be superior to low molecular weight heparin, the standard treatment.

One of the researchers, Dr. Alexander G.G. Turpie of McMaster University in Hamilton, Ontario, said he believes the drug is the "start of a new era of anti-coagulation." He expects it to eventually replace heparin.

The study, reported in Thursday's New England Journal of Medicine, was sponsored by the drug maker Sanofi-Synthelabo, which is seeking approval to sell the yet-unnamed drug in the United States and Europe. Two of the researchers, including Turpie, have been consultants to the drug maker, and the third works for the company.

Dr. Robert Handin of Bringham and Women's Hospital in Boston said the key advantage to the new drug is that it should be less expensive to manufacture than heparin, which is made from animal byproducts. He said injections of low weight molecular heparin cost about $200 a day.

The pharmaceutical company has not disclosed the drug's price.

Handin said the next step is the development of a pill form of blood thinner.

In the study, 933 patients who had total hip replacement surgery were given either one of five daily doses of the new drug or twice-daily doses of enoxaparin, a low molecular weight heparin sold as Lovenox. The blood thinners were given for a maximum of 10 days after surgery and the patients were monitored to see who developed blood clots.

The study showed two of the five doses worked substantially better than the heparin. The middle dosage reduced the risk of blood clots by 82 percent. In the new drug group, 1.7 percent of the patients developed blood clots versus 9.4 percent in the heparin group.

The two highest doses of the new drug were discontinued during the study because of bleeding, a side effect of blood thinners.

"Any anti-coagulant has the potential to cause bleeding. Pentasaccharides are no exception," Turpie said. "As it turns out, in doses which are effective, and indeed more effective than the comparative, the bleeding potential was no greater."

Results from three large, still-unpublished studies of synthetic pentasaccharide confirmed the drug works better in preventing clots in patients who had hip replacement, as well as hip fracture or knee surgery.

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On the Net:

New England Journal of Medicine: http://www.nejm.org

American Society of Hematology: http://www.hematology.org