If I understand your question, the additional testing is done in the only way that makes sense, on the population at large (that's taking the drug, of course).

If I understand your question, the additional testing is done in the only way that makes sense, on the population at large (that's taking the drug, of course). Drug companies and the FDA are pretty sure they understand the risks of the drug before the latter approves it, and I can't see it making sense to require even larger and longer formal double blind etc. trials. The whole process is already so expensive that it's probably at net killing people compared to backing off some. See GFK_of_xmaspast's link to the FDA page on Vioxx, where the drug company's monitoring effort pulled the plug before anything else.