It was just a month ago that I wrote about the frightening lack of agreement among FDA officials regarding drugs that were already on the market. Following Merck's (NYSE:MRK) Vioxx drug recall, investors and regulators alike were wondering what other drugs might be withdrawn for safety reasons, as well.

When drug safety was being discussed on Capitol Hill, whom did you believe? Was more research needed on five fairly prominent drugs, as Dr. David Graham, associate director for science in the FDA's Office of Drug Safety, testified? Or did you side with Dr. Sandra Kweder, the deputy director of the FDA's Office of New Drugs, when she said there no reason to single out those five drugs?

Suppose you had done a Google (NASDAQ:GOOG) search on Crestor, the cholesterol drug from AstraZeneca (NYSE:AZN) that Graham flagged as potentially causing acute kidney problems. You would have found lawyers seeking clients harmed by Crestor, as well as negative publicity from public interest group Public Citizen. Two weeks after the Capitol Hill testimony, Rep. Henry Waxman wrote to the FDA questioning whether Crestor advertising was misleading. It was not a pretty picture.

The picture has become downright ugly now that the FDA has sent a letter to AstraZeneca calling one of its newspaper ads for Crestor misleading and demanding that it be withdrawn. The FDA letter goes so far as to mention a Washington Post story that quotes Dr. Steven Galson, the FDA's acting director for Drug Evaluation and Research, as saying the agency had been concerned about Crestor "since the day it was approved." Yikes!

Crestor, approved in 2003 by the FDA and currently used in 64 countries, is in a class of drugs known as statins. One drug in that class was Baycol, a drug made by Bayer (NYSE:BAY) that was withdrawn from the market in 2001 because of concern about a rare and sometimes-fatal muscle disorder called rhabdomyolysis. Both AstraZeneca and the FDA have denied similarities between Crestor and Baycol.

Japan's equivalent of the FDA approved Crestor today for use in Japan. With all the controversy, if something were wrong, you would think that Crestor would not have been approved. Right? Hmmm.

Investors in Merck and Pfizer (NYSE:PFE) have learned a painful lesson from COX-2 (pain) inhibitors. Drug approval is sometimes a state of euphoria that can be followed by recalls or the need to defend a product from guilt by association.

It is probably too early for bottom-fishers to start buying the drug stocks being beaten up on Wall Street. But buyers prepare: It's unlikely we've seen the end of the recent spate of questions over FDA-approved drugs. Still, the long-term need for medicine and the impact of aging baby boomers in America are two trends that won't go away.

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Fool contributor W.D. Crotty does not own stock in any of the companies mentioned.