WASHINGTON - Reformulated nonprescription cold medications likely are effective, but further research is needed to determine whether higher doses are safe and work better, according to a panel of government advisers.

The Food and Drug Administration asked the panel to review the effectiveness of phenylephrine, the active ingredient in most decongestants available over the counter.

Johnson & Johnson's Sudafed PE, Wyeth's Dimetapp and Procter & Gamble's NyQuil are among the products that no longer contain pseudoephedrine, which is still available in some nonprescription products, although customers must provide identification to buy them. Products containing pseudoephedrine were put behind the counter at pharmacies in 2006 after Congress passed a law aimed at curbing the ingredient's use in the illegal processing of the highly addictive stimulant methamphetamine.

Researchers from the University of Florida had asked the government to re-examine phenylephrine, pointing to their own analysis showing no difference between patients taking the drug or a placebo.

By an 11-1 vote Friday, the FDA's panel concluded there was sufficient evidence that decongestants containing phenylephrine work.