Warning over common cold treatment sold in UK as US considers pulling it

Experts in the UK are discussing the future of a common cold treatment as the US Food and Drug Administration (FDA) considers pulling it from the shelves. Phenylephrine became widely used in cold and flu products as a safer alternative to pseudoephedrine - which can be used by criminals to make methamphetamine.

But recent studies question whether phenylephrine is effective when taken orally said Dr Hisham Al-Obaidi, lecturer in Pharmacy and Pharmaceutical Sciences at the University of Reading. In the UK there is now a discussion about the ethics of continuing to sell it.

Dr Al-Obaidi told The Conversation : "Continuing to sell a potentially ineffective product could harm public trust in over-the-counter (OTC) medicines. Consumers expect these products to be both safe and effective – not just safe – so evidence against phenylephrine may undo that trust."

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He added: "Fortunately, alternatives exist. As mentioned, pseudoephedrine is effective as a nasal decongestant, but it comes with purchase restrictions. Phenylephrine nasal sprays may also offer more direct relief. Phenylephrine and pseudoephedrine both relieve nasal congestion by constricting blood vessels in the nasal passages, which reduces swelling and helps ease breathing. However, their effectiveness depends on how well the drug reaches these target tissues.

"Pseudoephedrine is generally considered the more effective option, enters the bloodstream and reaches nasal tissues, acting directly on blood vessels to reduce congestion. Phenylephrine, though, is less effective when taken orally, as it is largely broken down before it can reach the nasal tissues in sufficient amounts.

"When swallowed, phenylephrine is quickly broken down by the liver and gut, a process called “first-pass metabolism”, which significantly reduces the amount that reaches the bloodstream and nasal tissues."

Dr Al-Obaidi said: "Research from several studies shows little evidence that oral phenylephrine effectively relieves nasal congestion. Findings suggest it may work no better than a placebo. Phenylephrine works better as a nasal spray, acting primarily on nasal linings with minimal absorption into the bloodstream. But prolonged use of decongestant sprays can lead to “rebound congestion”, a condition where nasal passages become increasingly congested as the effect of the spray wears off, often worsening symptoms over time.

"The medication causes blood vessels in the nasal passages to become less responsive over time. This can create a cycle of dependency and congestion. To avoid this, these sprays are recommended for short-term use only. While some products recommend limiting use to seven days, many health professionals suggest keeping it to three days to reduce the risk of rebound congestion.

"In the UK, the Medicines and Healthcare products Regulatory Agency (MHRA) has stated that no new safety concerns have been identified with phenylephrine. However, the agency continues to monitor its safety and effectiveness. While it is unclear if the MHRA will conduct a formal review, such a move would align with evidence-based standards and help protect consumer trust.

"With phenylephrine’s effectiveness now in question, consumers might consider other options. Alternatives like pseudoephedrine and nasal sprays for short-term use can offer reliable relief."