A federal advisory panel voted 20-17 to recommend a ban on the prescription pain killers Percocet and Vicodin because both narcotics are combined with acetaminophen in their formulation. Acetaminophen, an ingredient in Tylenol and many commonly used over the counter products, is known to cause liver damage with prolonged usage.

The panel’s 20-17 vote to recommend a ban on the combination drugs was one of 11 it took at a meeting called to advise the F.D.A. on problems arising from the extraordinary popularity of acetaminophen. In 2005, American consumers bought 28 billion doses of products containing the ingredient.

While the medicine is effective in treating headaches and reducing fevers, even recommended doses can cause liver damage in some people. And more than 400 people die and 42,000 are hospitalized every year in the United States from overdoses.

In hopes of reducing some of these accidents, the committee voted 24 to 13 to recommend that the F.D.A. reduce the highest allowed dose of acetaminophen in over-the-counter pills like Tylenol to 325 milligrams, from 500. And members voted 21 to 16 to reduce the maximum daily dosage to less than 4,000 milligrams.

But they voted 20 to 17 against limiting the number of pills allowed in each bottle, with members saying such a limit would probably have little effect and could hurt rural and poor patients. Bottles of 1,000 pills are often sold at discount chains.

The ultimate decision on the ban rests with the FDA. Expect pharmaceutical hissy fits if it seems like the FDA is even considering this route.