Why cold and flu tablets often fail to clear congestion

For many people, a blocked nose is the symptom that sends them to the cold-and-flu aisle. The box promises decongestion. The tablet is easy to take. In many familiar products, though, the ingredient meant to open the nose is oral phenylephrine, a decongestant swallowed in a pill rather than delivered directly into the nasal passages.

On labels, that distinction can be hard to see. Combination tablets may still ease fever, headache or body aches when they contain paracetamol or ibuprofen. The weak link is the decongestant claim attached to oral phenylephrine. A 2023 systematic review in Cureus and the FDA’s 2024 proposal to remove oral phenylephrine from over-the-counter monographs, the rulebook for certain nonprescription drugs reached much the same conclusion: swallowed phenylephrine does not reliably beat placebo, meaning an inactive comparison pill, for nasal congestion.

Anyone staring at a shelf of lookalike medicines is left with a practical question. If the evidence is this weak, why did oral phenylephrine end up in so many cold and flu tablets, and what should buyers look for instead?

Why oral phenylephrine ended up on pharmacy shelves

Pseudoephedrine, an older oral decongestant, has stronger evidence behind it. A 2005 trial in American Journal of Rhinology found pseudoephedrine improved congestion in adults with the common cold. Access changed because pseudoephedrine can be diverted to make methamphetamine. After it moved behind the counter in countries such as Australia, manufacturers needed a substitute they could keep in ordinary pharmacy aisles. Oral phenylephrine filled that space.

Commercially, the swap was tidy. Scientifically, it remained unsettled. As Jack Janetzki argued in The Conversation, the regulatory shift helped turn phenylephrine into the easy-to-sell default while the efficacy case stayed shaky. A medicine can stay familiar on shelves because of an old regulatory compromise, not because later studies keep making the case for it.

Bioavailability is part of the explanation. The term means how much of a drug reaches the bloodstream unchanged. Swallowed phenylephrine is broken down substantially before it can circulate. Pharmacologists call that first-pass metabolism: the gut and liver dismantle a large share of the dose before it can act elsewhere in the body. That route helps explain why a decongestant that can work locally as a nasal spray has looked far less convincing in tablet form.

What the evidence actually says

Evidence shifted over time rather than collapsing all at once. A 2007 meta-analysis in Annals of Pharmacotherapy was cautiously positive and suggested oral phenylephrine might help at some doses. Its conclusions rested on a smaller, older evidence base. Later re-examinations were less forgiving. The 2023 Cureus systematic review found only four studies that met its criteria and concluded oral phenylephrine performed no better than placebo.

After its own review, the FDA reached the same broad conclusion. In a 2024 press announcement, the agency said the proposal to remove oral phenylephrine was driven by effectiveness, not safety. The distinction matters. The concern is not that labeled use is unusually dangerous. It is that people buy the ingredient expecting one specific effect that the best recent evidence does not show reliably happening.

“it is not effective as a nasal decongestant”

Patrizia Cavazzoni, FDA

That FDA sentence pushed the debate out of academic journals and into medicine cabinets. Once a regulator says the evidence no longer supports the claim, the question shifts from whether the product helps a little to why it is still marketed as a decongestant.

Outside the United States, regulators have been watching the same evidence. In context provided by The Conversation’s review of the Australian market, a Therapeutic Goods Administration spokesperson said local monitoring of phenylephrine was based on efficacy concerns rather than safety concerns. Performance, not panic, is the point. Consumers are being told to check whether the ingredient doing the decongestant work has evidence behind it.

What can help congestion instead

A failed oral decongestant does not leave a blocked nose without options. Useful choices tend to be more specific, and less glamorous, than the all-in-one tablet promise. Topical decongestant sprays deliver the drug directly inside the nose, so they do not depend on surviving digestion first. For short-term relief, that route can work better.

Sprays still need restraint. Products such as nasal phenylephrine or similar topical decongestants are short-course tools, not something to use for a week straight. The usual ceiling is about three days because longer use can trigger rebound congestion, where the nose feels more blocked once the spray wears off.

Pseudoephedrine is another option with better evidence for congestion relief, though access is tighter. It is not appropriate for everyone, especially people with certain cardiovascular risks or those taking interacting medicines. When comfort is the main goal, other pieces of a combination tablet may still matter. Paracetamol or ibuprofen can help with aches and fever even if the phenylephrine portion does little for the nose.

A lower-tech option has some evidence behind it too. A 2015 Cochrane review of saline nasal irrigation found salt-water rinses were a reasonable adjunct for upper respiratory symptoms. Saline irrigation is not a blockbuster fix. It is one cold-care habit that lines up better with the evidence than the marketing on many tablet boxes.

“a range of safe and effective drugs and other treatments is available”

Theresa Michele, FDA

Read fairly, the cold tablet aisle is not full of fraud. It is full of products whose ingredients do different jobs. One of the most familiar decongestant ingredients has lost the evidence battle when taken by mouth.

What to watch before buying the next box

A useful label check starts with the active ingredient, not the brand. Which ingredient is supposed to relieve congestion? If the answer is oral phenylephrine, the strongest recent evidence suggests expectations should be modest. If the goal is broader symptom relief, the rest of the label may matter more than the decongestant line on the front of the packet.

Regulators and manufacturers now decide the next step. The FDA has proposed stripping oral phenylephrine from the over-the-counter monograph system, which would force reformulation or relabeling if finalized. Until then, shoppers are left doing a job the packaging does not make easy: separating ingredients that still have a role from one that became standard mostly because a better-supported alternative was pushed behind the counter.

References

1. Calderon Martinez E. The Use and Efficacy of Oral Phenylephrine Versus Placebo Treating Nasal Congestion Over the Years on Adults: A Systematic Review. Cureus 15(11). 2023. DOI:10.7759/cureus.49074
2. Hatton RC, Winterstein AG, McKelvey RP. Efficacy and safety of oral phenylephrine: systematic review and meta-analysis. Ann Pharmacother 41(3):381-390. 2007. PubMed
3. Eccles R, Jawad MSM, Jawad SSM, Angello JT, Druce HM. Efficacy and Safety of Single and Multiple Doses of Pseudoephedrine in the Treatment of Nasal Congestion associated with Common Cold. American Journal of Rhinology 19:25-31. 2005. Journal abstract
4. King D, Mitchell B, Williams CP, Spurling GKP. Saline nasal irrigation for acute upper respiratory tract infections. Cochrane Database Syst Rev (4). 2015. PubMed