(FORTUNE Magazine) - Looking back on pharmaceutical history can be an eye-opener--our parents and grandparents popped all kinds of dangerous pills, and the FDA never raised a finger. The real shocker, though, is that some of these drugs remain on the market, and the FDA still isn't doing much about them--even in instances where it's obvious that the drug never would have made it through the FDA today. Why are such drugs allowed to stay on the shelves?

Take the medicine that goes by the unwieldy name of acetylsalicylic acid. Concocted in 1897 by German chemist Felix Hoffmann, it's commonly given to patients for non-fatal conditions such as mild inflammation. Yet studies suggest that it and several drugs like it are fatal to at least 10,000 Americans a year. The victims die grisly deaths, typically from internal bleeding. The drug is linked to another, rarer side effect that strikes mostly children. The first symptoms are nausea and fatigue, but worse things follow: personality changes, confusion, and then, in the final stages, convulsions, coma, and death. The syndrome kills about half the children it afflicts.

Acetylsalicylic acid is dangerous stuff. Yet apart from requiring a warning on the bottle not to give the drug to kids, the FDA has never cracked down. Companies have long advertised the drug to unwitting consumers while giving short shrift to its risks. Moreover, the drugmakers have never sponsored the kind of rigorous clinical trials required for new drugs these days--the fatal side effects were discovered only because academics carefully documented them through the years. We seem to have all the ingredients here for another Vioxx or worse.

Except for one thing. The drug's household name is aspirin.