Dott. Carlo Sebastiano Tadeo
By Cameron Johnston
Special to DG News
NEW ORLEANS, LA -- February 15, 2000 -- Doctors have been telling patients for the better part of a decade now that a simple aspirin, once a day, can help prevent heart attacks and strokes. But with the advent of drugs such as ticlopidine (Ticlid, Roche), clopidogrel (Plavix, Bristol-Myers Squibb) and dipyridamole (Aggrenox, Boehringer Ingelheim), known collectively as "alternate antiplatelet agents", knowing what drug to recommend, and for what patients, has become more confusing.
At the annual meeting of the American Stroke Association, held in New Orleans on Feb. 10-13, Dr. Gregory Albers, a professor of neurology at Stanford University, in Palo Alto, CA, and director of the Stanford University Stroke Unit, outlined some of the pros and cons covering each of the drugs. Dr. Albers noted that all these drugs offer benefits for some patients, under certain circumstances.
As to the aspirin, how-much-is-enough controversy, he said: "It's hard to say what the most efficacious dose is, but our recommended dose is on the lower side."
Studies have shown that higher doses of aspirin are not always necessary to provide the same antiplatelet activity and that in some patients, a 50 mg dose can be just as efficacious as a 1300 mg/day dose (which, he stressed, should be the absolute daily maximum). At the same time, he said, if a person is going to develop gastrointestinal bleeding as a result of taking aspirin, it usually does not matter whether the person is taking a large dose or a small dose.
The clinical endpoints by which the alternate antiplatelet therapies are measured vary considerably, and it is crucial that doctors and their patients understand the differences before taking the drugs. "In order to make specific recommendation about 'first choice' and 'second choice' therapy, it's important to know not only the relative risk reduction but absolute risk reduction, too. How many events will we prevent?" he said.
Looking at absolute risk reduction, he said 10 strokes would be prevented per 1000 patients per year with clopidogrel, 25 strokes prevented per 1000 patients with ticlopidine, and 30 strokes per 1000 patients with dipyridamole. There would also be 10 fewer deaths per year for every 1000 patients taking clopidogrel, 25 fewer deaths per 1000 patients on ticlopidine, and 35 fewer deaths per 1000 patients on dypiridamole.
"The most cost-effective antiplatelet agent is clearly going to be aspirin. That’s the first line therapy. But first line therapy would be reasonable with any of the four agents, too," he said.
A high-risk patient is more likely to benefit from a drug that has the best absolute risk reduction. If the patient is allergic to aspirin, clopidogrel would be recommended. If the patient can tolerate low doses of aspirin, then dipyridamole, which has 50 mg of aspirin, would be the recommended drug. And if the patient has already had a transient ischemic attack while on aspirin therapy, the recommendation would be for either dipyridamole or clopidogrel. And, finally, if the patient has cardiac abnormalities, particularly atrial fibrillation, then the recommendation would be for warfarin, Dr. Albers said.
The guidelines Dr. Albers discussed have been adopted by the American Heart Association and the American College of Chest Physicians.
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