A pharmacy professor intends to file a citizen petition asking FDA to re-examine the effectiveness of the nasal decongestant phenylephrine after the agency refused a similar request by Congress.

Leslie Hendeles, Pharmacy Practice Department, University of Florida, said Sept. 26 he plans to file the petition by Oct. 4.

Hendeles co-authored a letter to the editor published in the July Journal of Allergy & Clinical Immunology, which stated a 10 mg dose of PE is "unlikely to provide relief of nasal congestion" and is less effective than pseudoephedrine (¹ Also see "Oral Phenylephrine An “Ineffective” Replacement For PSE – Pharmacists" - Pink Sheet, 31 July, 2006., p. 4).

Rep. Henry Waxman (D-Calif.) is encouraging Hendeles to file the petition. Waxman cited Hendeles' letter to the editor when he asked FDA in an Aug. 23 letter to convene an advisory panel meeting to revisit phenylephrine safety (² Also see "Waxman Seeks Phenylephrine NDAC Review; Cites Efficacy Concerns" - Pink Sheet, 28 August, 2006. p. 6).

The agency denied Waxman's request in a Sept. 13 letter, stating, "We are not aware of data that refute the conclusions of the advisory panel and subsequent OTC monograph review, and therefore, do not have substantive material to present for discussion at an advisory committee meeting."

However, FDA says it will reconsider convening an advisory panel "if sufficient additional information becomes available."

A citizen petition would "give all interested individuals the opportunity to weigh in on the issue" of PE's efficacy, the agency adds.

In its letter, FDA points out phenylephrine was deemed an effective decongestant in an August 1994 final monograph. Thus, a "difference of opinion alone is not a sufficient basis for FDA to take this to an advisory committee at this time."

The agency also provides responses to many of the issues raised in Hendeles' July letter to the editor.

For example, Hendeles asserts the bioavailability of phenylephrine is 38%, compared to 90% for pseudoephedrine.

In response, the agency states "a comparison of the relative bioavailability alone of two ingredients is not an adequate mechanism for comparing the efficacy of the ingredients."

"Clinical dosing for a drug generally would account for its bioavailability," FDA says.

The agency also comments that new drugs evaluated for approval "depend on" the manufacturer-supported unpublished studies that Hendeles criticized in his July letter.

"Studies that are unpublished cannot be viewed less favorably than published studies," the agency states. "When FDA is provided with the data from unpublished studies, FDA's review can be more rigorous than the review of editors for studies published in a peer reviewed article."

FDA points out it is not unusual for some studies to support the efficacy of a drug and for other studies to refute it.

"Aside from various study design and conduct issues, it is often difficult to consistently establish a clinically significant treatment effect for active ingredients in some disease processes during each trial conducted," the agency wrote.

"The conclusion about the effect of an active ingredient in light of both positive and negative trials is made based on the totality of findings and quality of the data," FDA added.

"The number of each type of study outcome is not generally a major factor" in the determination of a drug's efficacy, FDA concludes.

While Hendeles prepares to file the petition, Waxman is calling for FDA to compel the release of a study conducted by Schering-Plough that compares PE efficacy to pseudoephedrine.

The study, which has been completed but not yet released, is a Phase III, single-dose, investigator-blind, randomized, placebo-controlled, crossover study.

"If indeed there is proof that phenlyephrine is not effective in relieving symptoms of nasal congestion, consumers have the right to know," Waxman asserts.

Many OTC manufacturers have reformulated their cough/cold product lines with phenylephrine in light of nationwide retail restrictions on pseudoephedrine-containing products that took effect Sept. 30 (³ Also see "Pseudoephedrine Will Be Behind The Counter Across The Country By October" - Pink Sheet, 6 March, 2006., p. 5).

- Rebekah Moan

Phenylephrine Efficacy Will Be Questioned In Citizen Petition

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