Clot-Prevention Drug May Cause Blood Disease in Some
A widely used new blood thinner that is routinely given to heart patients after angioplasty appears in rare cases to trigger a deadly blood disease.
The drug, called clopidogrel (trade named Plavix) prevents blood clots and has been taken by more than 3 million people worldwide since its introduction two years ago.
For the first time, doctors have linked the medicine to thrombotic thrombocytopenic purpura, or TTP, a dangerous form of anemia. A report to be published June 15 in the New England Journal of Medicine but released online Thursday (https://www.nejm.org) describes 11 cases and one fatality among Plavix users.
Doctors say the benefits of the drug far outweigh this risk, which appears to be remote. But they say doctors should watch their patients closely for signs of the problem.
“My guess is that this will be a relatively rare complication, but it’s so important that everybody has got to know about it,” said Dr. Rodman Starke, research director of the American Heart Assn.
Plavix frequently is given for a month after angioplasty, in which a tiny balloon is inserted into a blood vessel to clear a blockage. The medicine is used especially in angioplasty patients who get wire mesh tubes called stents to keep their heart arteries from clogging up again. It also is given longer term to victims of mini-strokes to help prevent full-blown strokes, especially if they cannot take aspirin.
“We think it’s a great drug. It should be used,” said Dr. Charles L. Bennett of Northwestern University, who discovered the connection. “In the past, patients got the drug but did not have close monitoring. Our hope is doctors will be aware of this potential side effect and follow up after a week or two to see how they are doing.”
Plavix was designed specifically to avoid this problem. It replaced an older drug, ticlopidine, that caused TTP in about one of every 1,600 users. That was 100 times more frequent than in the general population, and one-third of these patients died.
Plavix is chemically almost identical to ticlopidine. But in extensive testing, it appeared to be safe.
TTP destroys red cells and the blood-clotting cells called platelets. Victims can have a wide array of seemingly unconnected symptoms, including anemia, kidney failure, abnormal heartbeats and neurologic problems that mimic strokes.
If the disorder is not recognized, about 80% of victims die. Patients can be saved by a blood-filtering process and the actual death rate is now between 10% and 20%. Bennett said some cases may be missed because doctors mistake them for strokes and other conditions.
Plavix’s makers, the drug companies Sanofi and Bristol-Myers Squibb, say new technical descriptions of the drug mentioning the possibility of TTP are being written for doctors.
