Poor Response to Plavix Has No Survival Impact, Study Finds

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plavix_aspirin_risks_side_effectsA newly published study reports that high platelet reactivity while on Plavix  (clopidogrel) after stent insertion was linked to some outcomes but not survival.

Poor response to dual antiplatelet therapy with Plavix and aspirin carried a 2.49-fold higher risk of stent thrombosis (clotting) and a 42 percent elevated risk of heart attack, both statistically significant, Dr. Gregg W. Stone of Columbia University Medical Center, and colleagues found. Mortality was similar regardless of platelet assay results (adjusted HR 1.20, P = 0.30), MedPage Today reports. The research, which was presented last year at the Transcatheter Cardiovascular Therapeutics meeting, has been published online in The Lancet.

The reason for the overall neutral impact appeared to be a tradeoff with clinically relevant bleeding events, which were 27 percent less likely with high residual platelet reactivity (P = 0.002). These latest results add to the negative 30-day findings from the ADAPT-DES and two failed clinical trials with platelet function testing, according to MedPage Today.

ADAPT-DES included 8,583 consecutive patients at 11 U.S. and German sites who got aspirin and clopidogrel after implantation of one or more drug-eluting stents. At one year, high platelet reactivity—208 or more P2Y12 Reaction Units (PRU) measured with the VerifyNow point-of-care assay—was associated with a 1.3 percent rate of definite or probable stent thrombosis compared with 0.5 percent among other patients, which translated to a propensity-adjusted hazard ratio of 2.49 for stent thrombosis (95% CI 1.43-4.31).

High platelet reactivity on aspirin had no significant associations with any outcome except bleeding risk (adjusted HR 0.65, 95% CI 0.43-0.99), according to MedPage Today. Because platelet reactivity on aspirin didn’t correlate with stent thrombosis, myocardial infarction, or death, “this raises questions as to the utility of aspirin in patients treated with drug-eluting stents,” Stone noted in a statement.

The researchers cautioned that “An adequately powered randomized trial is required before withholding aspirin in drug-eluting stent-treated patients (with or without chronic oral anticoagulation) can be recommended.”