In 2004, Merck pulled its painkiller Vioxx from the market. The drug was causing heart problems, strokes and deaths among patients in a large study that was under way at the time. Merck stopped the study early when those results became clear. Thousands of former Vioxx patients and their families are suing the company.

Now, documents obtained by NPR show that five years earlier, in 1999, during another large Vioxx study, patients had similar heart problems. But that study was not stopped.

Q&A: Monitoring Patient Safety

To learn more about data safety monitoring boards and their role in protecting patients who participate in drug studies, NPR turned to statistician David DeMets.

He says the current watchdog system is a good one, but that there are practical limits on the extent to which drug safety can be monitored.

Read the Q&A. June 8, 2006

During those five years, millions of Americans took Vioxx. And a Food and Drug Administration scientist has estimated that some 38,000 people who took the drug died.

Q&A: Vioxx Health Risks

Independent analysis of data sent to the FDA show that the cardiovascular risks from Vioxx begin shortly after a patient starts taking the drug. The data also indicate that the risks from Vioxx remain long after patients stop taking the drug.

NPR Health Editor discusses what’s known about Vioxx’s health risks. May 18, 2006

NPR’s Snigdha Prakash reports on why the earlier study wasn’t stopped and the public warned that Vioxx was unsafe.