By the time Merck withdrew Vioxx from the market in September 2004 out of concern that the pain relief drug was causing heart attacks and strokes, more than 100 million prescriptions for it had been filled in the United States alone. Researchers now estimate that Vioxx may have been associated with as many as 25,000 heart attacks and strokes. And more than 1,000 claims have been filed against the company. Evidence of the drug’s hazards was publicly available as early as November 2000, when the New England Journal of Medicine reported that four times as many patients taking Vioxx experienced myocardial infarctions as did those taking naproxen. In 2001, Merck’s own report to federal regulators showed that 14.6% of Vioxx patients suffered from cardiovascular troubles while taking the drug; 2.5% developed serious problems, including heart attacks. So why, if the drug’s risks had been published in 2000 and 2001, did so many doctors choose to prescribe it?