Nov. 5, 2007 (Orlando, Fla.) -- A new, more potent blood thinner works better than Plavix, the current standard treatment, at preventing heart attacks, strokes, and deaths from heart disease in people who undergo procedures to open up clogged coronary arteries, a study of more than 13,000 people shows.
But the new drug, prasugrel, also appears to raise the risk of life-threatening bleeding, particularly in people who have had a previous stroke, are elderly, or who have a low body weight.
Nevertheless, the benefits outweigh the risks for most people, says study head Elliott Antman, MD, a professor of medicine at Harvard Medical School and director of the Samuel A. Levine Cardiac Unit at Brigham and Women's Hospital in Boston.
For every 1,000 people treated with prasugrel as compared with Plavix, the new drug prevented 23 heart attacks and caused six major bleeds, Antman tells WebMD.
The findings, which were presented at the annual meeting of the American Heart Association (AHA), were simultaneously published online by The New England Journal of Medicine.
Blood Thinners Prevent Clotting
Due to an increased risk of blood clots, people who get stents -- tiny, mesh-like tubular structures that prop open clogged arteries after angioplasty -- are typically given blood-thinning treatment with a combination of Plavix and aspirin.
But too much of a good thing can turn nasty. If the drugs go too far at inhibiting platelets, bleeding can occur.
New Blood Thinner Prevents Heart Problems
The study involved 13,608 patients from 30 countries who were undergoing angioplasty and stenting due to heart attacks or serious heart-related chest pain. They were randomly assigned to take Plavix or prasugrel for an average of 12 months.
"We hypothesized that a regimen that ... inhibits the ability of platelets to clot more effectively would reduce events in patients undergoing [angioplasty]," Antman says. "It did."
Among the findings:
- Twelve percent of people taking Plavix suffered a heart attack or stroke or died of heart disease, compared with 10% of those on prasugrel, a 19% reduction in risk.
- Only 1% of people on the new drug developed clogged stents vs. 2.4% on Plavix, corresponding to a 52% reduction in risk.
- Nearly 10% of people given Plavix had a heart attack vs. 7% on prasugrel, a 24% reduction in risk.
- Major bleeding occurred in 2.4% of those on prasugrel, compared with 1.8% of those on Plavix. Fatal bleeding was uncommon, but four times more frequent with the new drug: 0.4% vs. 0.1% of people on Plavix.
- The risk of dying from any cause, 3%, was similar in both groups.
Prasugrel Benefits People With Diabetes
Further analysis showed that people with diabetes really benefited from the new drug. Those given prasugrel were 30% less likely to have a heart attack or stroke or die of heart disease or stroke, compared with those given Plavix.
But prasugrel proved particularly dangerous for people who had had a previous stroke. That group, which accounted for 4% of study participants, faced a significantly increased risk of having a heart attack or stroke, dying of any cause, or suffering a major bleed if they were given prasugrel.
People 75 and older, or who weighed less than 132 pounds, were neither helped nor harmed by the new drug. "They had less cardiovascular events and more bleeding, so the net benefit was near unity," Antman says.
He says he believes these people, who accounted for 16% of study participants, would benefit from a lower dose of the drug, though that remains to be tested.
Prasugrel More Potent Than Plavix
Prasugrel blocks platelet clumping more rapidly, more consistently, and to a greater degree than Plavix, Antman says.
That's important because some people who get stents develop blood clots and have heart attacks or die despite blood-thinning treatment with Plavix and aspirin, says Sidney Smith, MD, a past president of AHA and a heart doctor at the University of North Carolina in Chapel Hill.
"A more aggressive therapy might lower that risk," he tells WebMD.
Further Study Needed
While generally upbeat about the results, Smith and other experts called for further study to delineate which people would most benefit.
"The additional benefits of prasugrel are very impressive if, as suggested, we can accurately predict the minority of patients who would be at higher risk of bleeding from the drug," Smith says.
Raymond Gibbons, MD, a past president of the AHA and a cardiologist at the Mayo Clinic in Rochester, Minn., tells WebMD that he believes that prasugrel's benefits outweigh its risks.
"If I treat 150 patients, I'll have three fewer heart attacks at a cost of one major bleed. I think it's worth it," he tells WebMD.
With further study, "we'll be smarter about who should and shouldn't get the drug," Gibbons says.
Gordon Tomaselli, MD, chairman of the committee that picked which studies to highlight at the meeting and chief of cardiology at Johns Hopkins University School of Medicine in Baltimore, tells WebMD that he has concerns about the bleeding and would like to see more study before the drug is approved.
Prasugrel is being developed by Eli Lilly and Co. and Daiichi Sankyo Co., which funded the research.