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Coxibs May Inhibit Effects of Low-Dose Aspirin

Lab and animal studies show it blocks antiplatelet activity by binding to a subunit of COX-1

TUESDAY, Dec. 22 (HealthDay News) -- Celecoxib and other coxibs may interfere with the antiplatelet activity of low-dose aspirin, according to a study published online Dec. 16 in the Proceedings of the National Academy of Sciences.

William L. Smith, Ph.D., of the University of Michigan Medical School in Ann Arbor, and colleagues conducted in vitro experiments using biochemical measurements and X-ray crystallography. They also conducted experiments in dogs.

The researchers were surprised to find that celecoxib binds to one monomer of cyclooxygenase-1 (COX-1) and slows aspirin's COX-1-blocking action. They also found that administration of celecoxib to dogs interfered with low-dose aspirin's ability to inhibit arachidonic acid-induced ex vivo platelet aggregation.

"It will be important to determine if celecoxib impedes the action of low-dose aspirin in humans," the authors conclude. "A pharmacological effect of celecoxib on the action of low-dose aspirin on platelet aggregation in humans would necessitate modifying dosing regimens to provide clinically effective COX-2 inhibition while minimizing interference with aspirin inhibition of platelet COX-1."

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