Blood Thinner Doesn't Work for All

One-fourth of patients don't respond to Plavix in small study

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HealthDay Reporter

MONDAY, June 7, 2004 (HealthDayNews) -- New Israeli research suggests Plavix, a blood thinner often used in place of the troublesome clot buster Coumadin, doesn't work in many of the heart patients it's designed to help.

While Plavix doesn't appear to actually harm patients, about a quarter of those studied failed to respond to it, according to the small study. But the fact that Plavix (clopidogrel) still works much of the time indicates that it remains a good weapon for doctors to use, said cardiologist Dr. Stephen Wiviott, who co-wrote a commentary about the findings in the June 7 online issue of Circulation.

"What we do need to do is work harder to find either how to better use of this particular drug or find drugs that work for the people who aren't getting the benefit," said Wiviott, a cardiologist at Brigham and Women's Hospital in Boston.

Plavix is a fairly new drug and has been available in the United States only since 1997. Although it's expensive, cardiologists commonly use it to treat patients who've had heart attacks and strokes along with those undergoing angioplasties, operations that widen the arteries to prevent blockages. Like Coumadin (warfarin), its well-known cousin, Plavix makes it harder for the blood to clot and form new blockages.

Coumadin is a tricky drug to use because its levels must be closely monitored through blood tests to prevent the blood from becoming too thin. Severe bleeding, both internally and externally, can happen if the blood doesn't clot properly. "Coumadin, as a general statement, is a difficult drug to use," Wiviott said.

Although they accomplish the same thing, the two drugs work differently, with Plavix acting more like aspirin, which also thins the blood. Doctors continue to turn to Coumadin to treat some kinds of blood clots, including those in the legs and around the heart, said Dr. Eric Eichhorn, a cardiologist and medical director at the Cardiopulmonary Research Science and Technology Institute in Dallas.

In the new study, researchers in Israel examined the effects of Plavix on 60 patients who were treated with angioplasties and devices known as stents that keep the arteries open. The average age of the patients was 58.

In addition to aspirin treatment, the patients all got a high dose of 300 milligrams of Plavix after their angioplasties and then received smaller, 75-milligram doses for three months. To measure the blood's ability to clot, researchers turned to a test that gauges how well blood components known as platelets stick together.

In about one in four patients, the blood's ability to clot remained essentially unchanged. Those patients apparently had more severe heart attacks and were more likely to suffer from blood clots and heart attacks after their operations.

The authors acknowledged their study is small, and said more work needs to be done to determine if higher doses would make Plavix more effective in those patients.

Both Eichhorn and Wiviott said the findings won't hurt Plavix's reputation as an excellent drug. And while Eichhorn said the research is interesting, he added: "I don't know that it will change how we approach treating these patients."

More information

Get more details about blood thinners from the Texas Heart Institute.

SOURCES: Stephen Wiviott, M.D., cardiologist, Brigham and Women's Hospital, Boston; Eric Eichhorn, M.D., staff cardiologist, Dallas Heart Group, and medical director, Cardiopulmonary Research Science and Technology Institute, Dallas; June 7, 2004, Circulation online

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