The FDA assembled its outside advisers to take another look at phenylephrine, which became the main drug in over-the-counter decongestants when medicines with an older ingredient — pseudoephedrine — were moved behind pharmacy counters.

This week's two-day meeting was prompted by University of Florida researchers who petitioned the FDA to remove most phenylephrine products based on recent studies showing they failed to outperform placebo pills in patients with cold and allergy congestion.

The advisers essentially backed the conclusions of an FDA scientific review published ahead of this week's meeting, which found numerous flaws in the 1960s and 1970s studies that supported phenylephrine's original approval.

But FDA reviewers said their latest assessment reflects new testing insights into how quickly phenylephrine is metabolized when taken by mouth, leaving only trace levels that reach nasal passages to relieve congestion.

The group's negative opinion opens the door for the FDA to pull phenylephrine from a federal list of decongestants deemed effective for over-the-counter pills and liquids.

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