Too many of the wrong people would use the drug if it no longer required a prescription, advisers to the Food and Drug Administration concluded in a 10-2 vote against nonprescription sales of the medication.

"The patients couldn't figure out whether the drug was for them," said one FDA adviser, Dr. William Shrank of Harvard Medical School.

Merck argued that offering a low dose of Mevacor on open drugstore shelves, next to the aspirin, would persuade millions of people with moderately high cholesterol levels to take a pill that might prevent a first heart attack.

"This is a real opportunity," said Edwin Hemwall, executive director of Merck's worldwide OTC regulatory and scientific affairs. After the meeting, Hemwall said, "We are disappointed. We felt we presented a compelling case."

The FDA's advisers, however, were struck by how many people, in a study of almost 1,500 potential customers, wanted to buy the drug even though they were bad candidates.

One-quarter of people who wanted the pill did not have a high enough risk of heart disease to qualify, meaning they would face unnecessary side effects.

Worse still, 30 percent of very high-risk people -those who have heart disease or diabetes or had survived a stroke - wanted Mevacor; these are people who should be under a doctor's care. Merck says many of them are not seeing a doctor and that a little treatment is better than none.

Yet more than 30 percent of patients already taking prescription cholesterol-lowering drugs said they wanted the over-the-counter version. One-half said they would drop the more potent drug in favor of low-dose Mevacor. To the FDA advisers, that raises big questions about previously protected people setting themselves up for a heart attack.

"That's not good," said Dr. Kenneth Burman of Washington Hospital Center. "They're not getting monitored, they're not getting other medications and they're not getting counseling."