There is limited evidence that new formulations of over-the-counter cold medications actually relieve nasal congestion, according to FDA medical reviewers. Studies of phenylephrine, an ingredient recently added to many widely used nasal decongestants, are small, poorly designed and decades-old, agency staffers wrote in advance of a Dec. 14 meeting. (This is the briefing document).

Manufacturers, including Johnson & Johnson, Procter & Gamble and Wyeth, switched to phenylephrine after Congress enacted a law in 2006 that pseudoephedrine products be kept locked behind the counter and sold on request at pharmacies, the Associated Press reminds us, adding that the law is aimed at prohibiting the illegal processing of drug-store cold meds into the highly addictive stimulant methamphetamine.

The FDA reported that seven of 14 studies of phenylephrine didn’t show a significant improvement in nasal airflow at the currently used dosage, the AP writes. The FDA only requires two large, comprehensive studies to support effectiveness of a drug, however agency staffers say nearly all the phenylephrine studies were inadequate. “The studies are small and lacking many details necessary to provide a convincing demonstration of effectiveness,” the agency wrote.

Leslie Hendeles of the University of Florida says the findings support his view that the new formulations “aren’t any better than taking nothing,” and he supports upping the dosage to achieve effectiveness. Researchers at the University of Florida had requested the government examine phenylephrine’s effectiveness and said there is scant evidence they work better than a placebo at the 10-milligram dose in formulas available without a prescription.

Georgetown University professor Ken Dretchen disagreed, saying at least five of the studies reviewed by FDA are robust and show “without question” that phenylephrine works. Dretchen chairs Georgetown’s department of pharmacology and was hired by the Consumer Healthcare Products Association to review data on the ingredient. The group’s members include Johnson & Johnson, Wyeth and most companies that make OTC meds.

Several studies that showed poor results for phenylephrine “were not designed to be able to pick up subtle differences,” in nasal airflow, Dretchen added. He is scheduled to present CHPA’s case at the FDA meeting. “FDA may decide through its advisory panel that it wants to run one more trial just to be sure of these results,” Dretchen tells the AP. “But from my own vantage point, I’m satisfied.”

Researchers from the University of Florida are expected to counter at the meeting that more research is needed to find an effective phenylephrine dose. “What we need is a large-scale scientific study in modern times looking at different doses to determine which will actually let you breath through your nose,” Hendeles tells the AP, pointing that most of the phenylephrine studies were performed in the 1960’s and 1970’s.

His group recommends increasing the dosage available without a prescription to 25 milligrams, the AP reports, adding that FDA review documents suggest there is mixed evidence the increased dose would improve effectiveness.