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ASA-Clopidogrel Combination Enhances Antiplatelet Response in Cerebrovascular Disease: Presented at ISC

By Paula Moyer

SAN DIEGO, CA -- February 10, 2004 -- Therapy that combines acetylsalicylic acid (ASA) and clopidogrel (Plavix) has more effective antiplatelet activity than ASA does alone in patients with prior cerebrovascular disease, according to findings presented here February 5^th at the American Stroke Association's 29^th International Stroke Conference.

Patients receiving such therapy are less likely to show ASA resistance, according to investigator Mark J Alberts, MD, Professor of Neurology, Northwestern University Medical School, Chicago, Illinois. Dr. Alberts noted that the combination shows an enhanced antiplatelet effect independent of the dose of ASA as well as of any coating preparation.

Evidence shows that ASA resistance develops in 20% to 35% of patients with atherothrombotic vascular disease who take various doses of ASA. Dr. Alberts and colleagues were interested in the feasibility of combination therapy because prior research showed an enhanced antiplatelet effect when clopidogrel was added to ASA. They therefore studied the frequency of ASA resistance in patients taking ASA plus clopidogrel among inpatients and outpatients who had previously been diagnosed with cerebrovascular disease.

All patients were taking ASA combined with clopidogrel. The investigators measured the subjects' antiplatelet effects with technology that used a mixture of epinephrine and collagen, and a mixture of collagen and adenosine diphosphate (ADP) to cause platelet activation. They also collected information on patients' ASA dose and formulation, along with their demographic data.

The patient base consisted of 40 women and 29 men. Among these, 64% were Caucasian, 16% were African-American, and 4% were Asian. In the overall group, 43% subjects were taking 81 mg daily of ASA along with 75 mg daily of clopidogrel, while 57% of patients were taking at least 325 mg daily of ASA with clopidogrel. From the information the investigators obtained, 29% were taking a coated ASA preparation and 19% were taking an uncoated formulation.

Results showed that 27% of the patients had normal platelet function as tested by combined epinephrine and collagen. There was an antiplatelet effect in 74% of patients on an ASA dose of 325 mg daily along with clopidogrel. This effect also was seen in 70% of those who were taking 81 mg daily ASA with clopidogrel. This difference was not significant, according to Dr. Alberts.

Whether or not the ASA was coated did not influence the rate of resistance, seen in 30% of patients taking the coated version and in 26% of those taking the uncoated version. The average ASA resistance rate was 27% in those taking ASA plus clopidogrel, compared to 47% in a database of patients who were only taking ASA and had been admitted with a stroke or transient ischemic attack (P < .02). The investigators had data regarding the collagen-ADP test for 49 patients, of whom 38% showed a therapeutic response, according to Dr. Alberts.

Dr. Alberts said these findings show potential for this therapeutic combination in patients with cerebrovascular disease.


[Study title: Antiplatelet Effect of Aspirin Combined with Clopidogrel in Patients with Cerebrovascular Disease. Abstract P27]

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