Is Plavix Resistance due to Noncompliance?

February 1st, 2010 | Sources: Medscape

Subjects:

Plavix, the clot-busting blockbuster marketed by BMS and Sanofi, is never out of the news for long.

One story that developed legs in the last year for example, was the finding of apparent marked variability in responsiveness to the drug. This begat calls for personalized prescribing of Plavix based on genetic markers, and warnings that Nexium-The PlavixPurple Pill—impaired its effectiveness, thus creating an increased risk of vascular complications.

Now it seems, the worm has turned again on this story. Victor Serebruany and colleagues have reported that the issue of Plavix nonresponsiveness may be caused by something rather mundane: non-compliance with the drug.

To reach this conclusion, the scientists obtained blood samples from 422 heart disease patients and 209 poststroke patients that had platelet activity tests performed before and after Plavix use.

They tested these archived blood specimens for a chemically stable, carboxyl metabolite of Plavix, and then defined Plavix noncompliance to be a very low plasma concentration of this inactive metabolite.

They found that 138 patients (22%) were in fact noncompliant. Noncompliance was more frequent in stroke victims (38%) than cardiac disease patients (14%).

be different“Some of the patients whom we would classically describe as ‘resistant’ to clopidogrel, in that they showed low levels of platelet inhibition, in fact didn’t actually have clopidogrel on board,” Serebruany told Medscape.

“The whole variability issue with clopidogrel (Plavix) is not such a big deal,” Serebruany added. “It has been hyped by the manufacturers of the newer antiplatelet agents. If we did studies with these agents, they would show variability, too.”

“Future antiplatelet trials should recognize noncompliance as a critical confounding factor, and every attempt should be made to minimize and strictly monitor prescribed antiplatelet regimens,” the authors concluded.


 

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