Updated from 9:52 a.m. ESTATLANTA -- A clinical study has found that adding the blockbuster anticoagulant Plavix to aspirin isn't significantly better than aspirin on its own in lowering the risk of heart attacks, strokes or cardiovascular deaths. Plavix, the second-biggest-selling drug in the world, is marketed by Sanofi-Aventis ( SNY) and Bristol-Myers Squibb ( BMY). Last year, sales of Plavix were nearly $6.3 billion, trailing only Lipitor from Pfizer ( PFE). The results from the study, known as Charisma, don't affect Plavix's currently approved use as an anticlotting agent, but Bristol-Myers and Sanofi-Aventis had been hoping to gain expanded indications for the drug. The trial found that combining aspirin and Plavix, also known as clopidogrel, didn't demonstrate a statistically significant reduction in the chance of a patient having a heart attack, stroke or death by a cardiovascular cause when compared with a placebo and aspirin. More than 15,000 patients took part. "