STUDY
Low-Dose, Enteric Aspirin Often Fail to Produce Antiplatelet Effect: Presented at ISC
By Charlene Laino
Special to DG News
PHOENIX, AZ -- February 19, 2003 -- Low-dose and enteric-coated aspirin fail to produce a significant antiplatelet effect in most patients who take the drug to prevent cardiovascular disease, a new study suggests.
However, full-dose uncoated aspirin appears to be more effective, reported Mark Alberts, MD, director of the Stroke Program at Northwestern Memorial Hospital in Chicago, Illinois, United States. Dr. Alberts presented the results here on February 14th at the 28th International Stroke Conference.
Although aspirin is used routinely for the prevention of vascular events in patients with cerebrovascular disease, its efficacy is limited, with risk reductions of only 20%, Dr. Alberts said. His group undertook the study to test the hypothesis that aspirin may not have a significant antiplatelet effect in some patients, and the lack of an effect may be dependent on the drug's dose and formulation.
The researchers prospectively collected data on aspirin dose, type (coated or uncoated), demographic factors and homocysteine level in 126 patients, whose average age was 61.9 years. They all had an ischemic stroke, transient ischemic attack or stenosis of a cerebral artery. The antiplatelet effects of aspirin were measured using the platelet function assay (PFA) 100 device, which assesses antiplatelet effects using a flow aperture closure paradigm, Dr. Alberts said.
Twenty-seven percent of patients were taking 81 mg of aspirin daily and the rest, 325 mg. About one-third used an enteric-coated preparation.
Overall, 38% of all patients had a normal platelet function assay by the PFA100 test. Of patients taking low-dose aspirin, 56% had normal platelet function compared with 28% of those taking 325 mg of aspirin.
Among patients taking an enteric-coated preparation, 65% had normal platelet function, regardless of the dose, while 75% of patients taking uncoated aspirin did show reduced clotting.
Routine testing of antiplatelet effects in patients receiving aspirin may be warranted to optimize dosing and efficacy, Dr. Alberts concluded.
[Study title: Lack Of Antiplatelet Effect In Patients Receiving Aspirin
Abstract P291]