When Held's team looked at each group individually, they found no statistically significant difference for heart attack and stroke and no significant difference in major bleeding from the bypass operation itself.
The two drugs work in different ways.
Plavix needs the body to convert it to an active form, which poses some problems. Last week, the U.S. Food and Drug Administration required Bristol-Myers Squibb and Sanofi Aventis, the makers of Plavix, to add a "black box" warning to the drug's label, alerting doctors and patients that some patients cannot fully convert the drug, so it may be less effective for them.
Brilinta, which is in a different class of drugs, does not rely on metabolic conversion, so it acts faster and clears the body faster than Plavix. This enables quicker recovery of normal platelet function, the researchers say.
But Held can't explain the difference in the rate of death. "That's the billion dollar question," he said.
"Right now we don't understand the mechanism. We see the difference in mortality, but we cannot explain it in differences in bleeding so there has to be some other effect explaining the difference," Held said.
The PLATO study was funded by AstraZeneca, the maker of Brilinta.
Results of another study presented at the meeting Tuesday found that the drug Tekturna (aliskiren) given to patients after a heart attack did not improve heart function as researchers had hoped. In that trial -- called the Aliskiren Study in Post-MI Patients to Reduce Remodeling (ASPIRE) -- Tekturna, which blocks the hormone renin, was given to patients along with common blood pressure-lowering drugs. But the researchers found it provided no additional benefit in heart function and only s
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