A nice summary of frequently asked questions to the Vioxx recall from WebMD, including more information on the trial:
What evidence supports the withdrawal?
Merck’s decision to withdraw Vioxx from the market is based on new data from a trial called the APPROVe trial. In the APPROVe trial, Vioxx was compared with placebo (sugar pill). The purpose of the trial was to see if the 25 mg dose of Vioxx was effective in preventing the recurrence of colon polyps. This trial was stopped early because there was an increased risk of serious cardiovascular events, such as heart attack and stroke, after 18 months of continuous treatment with Vioxx.
Why wasn’t the APPROVe trial stopped earlier?
The APPROVe trial began enrollment in 2000. The trial was being monitored by an independent data safety monitoring board. It was not stopped earlier because the results for the first 18 months of the trial did not show any increased risk of cardiovascular events from taking Vioxx.
Update:
More from the Merck website and the FDA.
