Staff researchers at the Food and Drug Administration raised questions Wednesday about how well consumers understand guidelines for Mevacor, a cholesterol fighter that Merck ( MRK) wants to convert from prescription to over-the-counter status. The FDA staff report didn't make a formal recommendation, but it focused on how well consumers would understand the benefits and possible risks of an over-the-counter product and understand the drug's label. As is common practice, FDA staffers posed questions and observations for FDA advisory panel members who will meet Thursday and Friday to discuss whether Mevacor is considered safe as an over-the-counter (OTC) product. The FDA isn't required to follow recommendations by advisory panels, but it usually agrees. If Merck prevails, Mevacor would be the first OTC cholesterol drug in the U.S. A nonprescription version of Merck's Zocor has been available in the U.K. since July. Four years ago, advisory panels rejected a similar request by Merck to take Mevacor over the counter. The FDA agreed, saying the company hadn't proved that the benefits outweighed the risks and hadn't demonstrated that consumers could take the drug safely without a doctor's prescription and supervision. At the time, Merck was seeking OTC approval for a 10-milligram pill. This time, it is asking the FDA to approve a 20-milligram pill that would be aimed at people who are at risk of having a cardiovascular problem in the next 10 years. Given the potential side effects, the FDA staff report asked whether Merck "provided adequate justification" for not requiring liver-function test-monitoring in an over-the-counter setting. It also wondered whether the potential liver-damage risk of nonprescription Mevacor in individuals with liver disease had been adequately addressed. The staff report said cholesterol drugs known as statins -- Mevacor belongs to this group -- can raise certain liver enzymes, a signal for possible liver damage. However, the staff's research of medical databases shows that "these increases rarely result in serious liver injury; and in the few reports of liver injury, attribution to statin use cannot be established."