The decongestant used in Sudafed and Benadryl is likely no better than a dummy pill, according to the US medicines regulator.
Advisers to the Food and Drug Administration (FDA) voted unanimously that phenylephrine, the ingredient used in popular High Street medications, is “not effective” at standard doses.
But an FDA panel said after a two-day review that the decongestant was no more effective than a placebo.
Jennifer Schwartzott, the patient representative on the panel, said: “I feel this drug in this oral dose should have been removed from the market a long time ago.
“Patients require and deserve medications that treat their symptoms safely and effectively and I don’t believe that this medication does that.”
If the FDA decides to accept the panel’s recommendations, pharmaceutical giants including Johnson & Johnson could be forced to pull their oral medications containing phenylephrine from the shelves in the US.
This would not impact sales of the drug in the UK, where medicines are regulated by the Medicines and Healthcare products Regulatory Agency (MHRA).
FDA reviewers said that phenylephrine is likely to be ineffective as it metabolises quickly when taken orally, leaving only trace levels that reach nasal passages to relieve congestion. The drug appears more effective when applied directly to the nose, in sprays or drops.
Drugs that contained phenylephrine generated almost £1.4bn in sales last year in the US, according to data presented by the FDA on Monday.
Advisers told the FDA that studying the ingredient at a high dose was not possible as it can push blood pressure to dangerous levels.
The review came after University of Florida researchers recently petitioned the FDA to remove phenylephrine products based on recent studies showing they failed to outperform placebo pills in patients with cold and allergy congestion.
A review by the same researchers in 2007 found that studies on the effectiveness of phenylephrine were inconclusive.