Last Sunday a panel of cardiologists told more than 5,000 people that high cholesterol patients shouldn’t take Vytorin and Zetia except as a last resort. Made by Merck and Schering-Plough, these widely prescribed cholesterol-lowering drugs are taken by about four million Americans.

A January clinical trial of 720 patients found that Vytorin users didn’t benefit any more from their pricey, heavily-advertised drug than patients taking generic statins (Vytorin costs about $112 per month, while a generic statin costs $32 to $90 depending on the dosage). These studies challenge the traditional belief that lowering LDL (low-density lipoprotein i.e. “bad cholesterol”) means a reduced risk for heart attack.

Dr. Keith Aaronson from the University of Michigan admits he knew little about Zetia when he formerly prescribed it to high-risk patients: “The bottom line is that most of us, and I include myself, have been blindly bought into the idea that any drug that lowers LDL must be good,” he told Forbes.

Zetia may have been a perfect fit, given the climate of modern American medicine. A combo pill, Vytorin, doubled sales by combining it with the cheaper, generic Zocor. Almost no hard evidence supported its use. But it caused no annoying side effects, like a flushed face or achy muscles, which meant fewer patient complaints. Consumers came to the doctor’s office convinced by a stunningly effective ad campaign claiming that Zetia or Vytorin was right for them. Doctors, strapped for time by insurers, didn’t have the time to argue.

Merck and Schering first announced that their drug might not be all that back in January. After the companies issued their official statement, the FDA said it would review the data, expressing astonishment at the result. The FDA made no comment last week after the release of this additional analysis.

TNS Media Intelligence, as reported by Star Tribune, shows Merck and Schering-Plough spent about $472.8 million on advertising since the drugs hit the market, with about $5 billion in sales last year. According to GoozNews on March 31, this huge profit “is testimony to the power of marketing, and the poverty of medical and regulatory science.”

The day after cardiologists criticized Vytorin and Zetia, both stocks hit 12-year lows. Shering-Plough shares fell 26% and Merck shares fell 15%.

With Vytorin’s market potential suddenly shrinking, Merck has a new cholesterol drug on the way—Cordaptive. Merck expects to hear back from the FDA before July on whether it will approve Cordaptive. Heart patients deserve to know whether it works better than drugs already on the market before they start taking yet another high priced pill.