Last year, FDA advisers unanimously voted that oral phenylephrine is ineffective. //

No other lab was ever able to replicate the positive results from those two studies. And when FDA scientists carefully looked through the data, they found evidence that some of the numbers could have been fudged and that the results were "too good to be real."

As a final nail in phenylephrine's coffin, modern studies suggest that when phenylephrine is taken orally, it's highly metabolized in the gut, leaving less than 1 percent of the consumed dose as active in the body. The finding explains why oral doses don't cause the constriction of blood vessels throughout the body that could lead to an uptick in blood pressure—a side effect sometimes seen with pseudoephedrine. While researchers initially thought the lack of blood pressure increases was a positive finding, in retrospect, it was a hint that the drug wasn't working.

With that, a panel of advisers for the FDA voted unanimously, 16 to 0, that oral doses of phenylephrine are not effective at treating a stuffy nose.