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Plugged-up sinuses? Stuffy nose? Don't bother taking the usual decongestant.

It turns out that phenylephrine – an active ingredient in many over-the-counter cold and flu remedies – isn't so active after all. Taken orally, phenylephrine is no better than a sugar pill, according to a study published in the September-October issue of the Journal of Allergy and Clinical Immunology: In Practice.

The study is the third in a series of "modern, rigorous" studies showing that oral phenylephrine is ineffective in treating nasal congestion, said Dr. Randy Hatton, a clinical professor of pharmacotherapy at the University of Florida. In an accompanying editorial, Hatton and co-author Dr. Leslie Hendeles, also at the University of Florida, called on the U.S. Food and Drug Administration to pull oral phenylephrine from the burgeoning market of pills and hot-beverage treatments for nasal congestion.

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"Consumers should not be buying and using a product for which there is insufficient evidence that it works," Hatton said in an interview.

In the most recent study, researchers treated 539 adults suffering from seasonal allergic rhinitis (sneezing and runny nose) with phenylephrine for seven days, in doses ranging from 10 milligrams to 40 milligrams – four times the normal dose. Regardless of the dose, "there was no demonstrated beneficial effect, and no difference between phenylephrine and placebo," Hatton said.

Although the study looked at stuffy noses due to allergies, Hatton said the findings should apply to cold sufferers as well. "Nasal congestion is nasal congestion." Both seasonal allergies and cold viruses cause the blood vessels in the nose to dilate, resulting in increased fluid secretion and the feeling of being plugged up.

Decongestants such as phenylephrine are designed to constrict the blood vessels. But oral decongestants must be absorbed through the gastrointestinal tract before they hit the blood stream, and they cause blood vessels to constrict throughout the body – not just the nose. "It's a really inefficient way to treat nasal congestion," Hatton said.

Phenylephrine has been widely used since the mid-2000s as a replacement for pseudoephedrine, a more effective oral decongestant. But since pseudoephedrine is a major ingredient in the making of illegal methamphetamine, this medication is no longer sold over the counter in Canada except in certain products that include other medications.

More often than not, phenylephrine is also combined with other medications, such as acetaminophen for pain and antihistamines, which can have a drying effect. People might think they're breathing easier after taking a remedy that contains phenylephrine, "but it's the other ingredients that might be contributing to that perception," Hatton said.

Instead of oral phenylephrine, Hatton and Hendeles recommend that patients use non-prescription oral pseudoephedrine from behind the counter or topical decongestant sprays, which constrict blood vessels specifically in the nose.

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While phenylephrine pills don't work, "nasal sprays with phenylephrine are very effective," Hatton said.

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