The government is questioning if too many of the wrong people will take cholesterol-lowering Mevacor if it's sold without a prescription, days before Merck & Co. makes its third try to move the drug over the counter. Merck says selling a low dose of this long-used medication on drugstore shelves, next to the aspirin, could get millions of people at moderate risk of heart disease important treatment that they otherwise may miss. A preliminary Food and Drug Administration review released Tuesday agreed that nonprescription Mevacor would be "a reasonably safe and effective" option - if consumers used it as directed.

But when Merck tested if consumers could judge who was a proper Mevacor candidate, only 20 percent answered all the questions completely correctly - 50 percent if researchers counted people who said they'd check some things with their doctor before purchasing, concluded FDA's lead medical reviewer.

Moreover, about 30 percent of people who already were diagnosed with heart disease, diabetes or had had a stroke wanted to purchase over-the-counter Mevacor, people who need a doctor's care, the FDA documents say.

The studies "have not convinced this reviewer that there is adequate consumer comprehension of the proposed product label to ensure safe and effective use of this product," the preliminary assessment concluded.

Merck argues that most people made the right decision on whether they should buy OTC Mevacor even if they missed some answers.

On Thursday, Merck will present its case to the FDA's independent scientific advisers, hoping they will recommend that Mevacor become the first in the family of cholesterol-lowering "statin" drugs to be sold in this country without a prescription. Twice before, FDA has said no.