Documents obtained by NPR show that five years before Vioxx was pulled off the market, doctors monitoring the safety of the drug knew that it increased the risk of heart attacks. These doctors were part of a panel overseeing a study of Vioxx. Independent experts tell NPR that the study should have been stopped at the first sign that Vioxx increased the risk of heart attacks and strokes. They say that would have prevented tens of thousands of deaths. The safety panel and Merck say it wasn't clear whether Vioxx was causing the problems. A report from NPR's Snigdha Prakash continues.