Each year, millions of people experience the annoying and uncomfortable symptoms of a persistent cough. Typically caused by mild infection of the respiratory tract, subacute coughs (a cough of 3 to 8 weeks duration) are far from a medical emergency, yet they drive people to doctors’ offices and are a large contributor to the crisis of unnecessary antibiotic prescriptions.

If a physician has ruled out any non-infectious or serious causes and is able to talk their patient down from demands for unsuitable treatments, they may instead recommend fluids, rest, and patience. For those in need of relief, they might recommend one of the handful of over-the-counter or prescription cough medicines. These agents – which work by lubricating the throat, reducing inflammation, or suppressing the cough reflex – can be found in any drugstore and generate more than $4 billion in worldwide sales each year.

There’s just one problem, they might not work.

According to a new analysis by researchers at the University of Basel in Switzerland, seven of the most frequently used cough medicines showed no clear benefit over placebos for improving cough severity.

“This review indicates that, despite being one of the most common causes for seeking medical advice in primary care, there is no beneficial treatment for subacute cough,” the team wrote in the British Journal of General Practice.

“Therefore, considering the problem of overtreatment, spending time with the patient to explain the illness might be crucial for patient satisfaction.”

Lead author Dr Benjamin Speich and his colleagues scoured the literature for studies that assessed a cough treatment using patient-reported cough severity scores (so the studies could be compared to one another). They found six investigations that covered seven treatments: one study looked at codeine and a different type of opioid compared with a placebo, and the remaining six covered salbutamol plus ipratropium bromide (an inhaled combination sold under the names Combivent, DuoNed, and Breva), montelukast (an oral tablet also prescribed for asthma and allergies), fluticasone propionate (an inhaled drug and over-the-counter allergy spray commonly known as Flonase), inhaled budesonide (a steroid sold under the brand name Pulmicort), and the home remedy treatment of a teaspoon of gelatin three times a day.

Interestingly, the study on fluticasone did find a slight yet significant improvement in cough scores compared to a placebo after 14 days, and fewer patients given the active drug requested additional treatment. But Speich’s group remains skeptical, citing a mixed cohort of acute and chronic cough patients and vague cough scoring methods.

Montelukast, codeine, the alternate opioid, and budesonide failed to show better efficacy than a placebo at any time point, and patients taking gelatine did not fare better than those randomized to continue their previous treatment.

Of course, the results of one study for each drug is not enough to completely discount the possibility that these treatments can provide relief. However, the authors point out that other literature reviews have also found a lack of strong support for existing cough remedies. They then highlight that no new cough treatments appear to be in development.

“Remarkably, antitussive [cough-relief] agents that are currently used in clinical practice were developed several decades ago and there has been little progress in the meantime, although the need for effective antitussive treatments seems obvious,” the team concluded.