The U.S. Food and Drug Administration through one of its panels has said that new studies are needed to assess the effectiveness of the current dosage of Phenylephrine, a decongestant, although it appears that the current 10mg dose seems enough for over-the-counter use.

The panel was convened after three professors from the University of Florida petitioned the drug regulator alleging that the current dosage is not effective and it needs to be increased. The chemical has been widely used over the couple of years after it gradually replaced pseudoephedrine, a more effective but more dangerous drug.

Phenylephrine has been approved by the FDA in 1976 based on studies at the time. Thus, it is necessary to reassess its effects according to new testing standards. Pharmacists Leslie Hendeles and Randy Hatton of the University of Florida suggested in 2006 that oral phenylephrine is ineffective as a decongestant at the 10 mg dose used, claiming that six tests showed no significant difference between phenylephrine and placebo.

“As pharmacists we have always avoided this drug,” said Paul Doering, a University of Florida professor of pharmacy. “We all know that it isn’t absorbed into the bloodstream well enough.”

Hendeles also last year that a higher dose may work, but no research has been published regarding safety at higher doses.

Pseudoephedrine has been replaced with the less effective phenylephrine by drug makers to avoid their products being sold behind the counter. “It’s taking a moderately effective nasal decongestant (pseudoephedrine) and replacing it with an ineffective medication (phenylephrine),” said Dr. Miles Weinberger, director of the pediatric allergy and pulmonary division at the University of Iowa College of Medicine.

However, the FDA panel voted 11-1 vote that available data was "supportive" of the effectiveness of phenylephrine at 10 milligrams, the dose sold over the counter. The same FDA committee, in a subsequent 9-3 vote, also urged new research to see if a higher 25-milligram dose worked and was safe.

However, the Consumer Healthcare Products Association (CHPA), which represents drugmakers, said in a statement that there are no convincing data that a 25-milligram dose is necessary.

Phenylephrine is also available as a nasal spray, in 1% and 0.5% concentrations.