According to FDA panel experts who reviewed the latest research on the long-questioned phenylephrine, a drug ingredient used in several leading decongestants used by millions of Americans looking for relief from a stuffy nose, is likely no better than a dummy pill.

"We believe that these new clinical pharmacology and clinical data are consistent, substantial, and believable, and they confirm that orally administered [phenylephrine] is not effective at any dose that can be developed and still provide a reasonable margin of safety," the agency's reviewers wrote in their report.

Advisers to the FDA voted unanimously against the effectiveness of the phenylephrine found in popular versions of Benadryl, Mucinex, Tylenol, and other medications stocked on store shelves.

For the panel's recommendations, three oral decongestant ingredients, phenylpropanolamine (PPA), pseudoephedrine (PSE), and phenylephrine hydrochloride, were included.

PPA was removed from OTC use due to safety issues.

After the Combat Methamphetamine Epidemic Act of 2005, PSE became regulated as 'behind-the-counter,' limiting its use in the OTC setting and leaving PE as the only remaining OTC oral decongestant.

If the FDA follows through on the panel's recommendations, Johnson & Johnson's (NYSE:JNJ) recent spinoff Kenvue Inc (NYSE:KVUE), Bayer AG (OTC:BAYRY), GSK Plc's (NYSE:GSK) spinoff Haleon Plc (NYSE: HLN), and Procter & Gamble Company (NYSE: PG), Reckitt Benckiser Group (OTC: RBGLY) (OTC: RBGPF) and other drugmakers could be required to pull their oral medications containing phenylephrine from store shelves. 

The manufacturers and pharmacy retailers could also see some impact if the FDA deems phenylephrine ineffective.

Wall Street Journal, citing Research firm IRI, notes that in 2021, OTC products designed to address cough, sinus, and flu symptoms, including phenylephrine-containing pills, generated approximately $5 billion in sales.

Pharmacy retailers to watch out for include CVS Health Inc (NYSE: CVS), Walgreens Boots Alliance Inc (NASDAQ: WBA), and Rite Aid Corp (NYSE: RAD), among others.