Cough Syrup – More Marketing than Science?

By Catherine Couturier – The Rumor Detector – Agence Science-Presse

You are sick with a cough. Are you tempted to buy the cough syrup they sell at the pharmacy?

Not so fast. Years of scientific research has yet to show that these products work, as the Rumor Detector has uncovered.

Indeed, since the beginning of this century, research has effectively not found any obvious advantages to cough syrup as measured against a placebo.

For example, in 2007, a literature review raised doubts about the efficacy of one ingredient, codeine, long considered the very best cough suppressant on the market. Codeine is generally no better at suppressing coughs than is a placebo. Neither is dextromethorphan, another key ingredient in many cough syrups.

Studies with children have concluded that neither dextromethorphan nor diphenhydramine (Benadryl) are more effective than a placebo. But the lack of hard evidence has pevented authorities from either recommending or discouraging the use of cough medicines for children. Indeed, a systematic Cochrane Review conducted in 2014 showed that there is no real proof anywhere that syrups on sale do anything to suppress a cough among adults or children.

A Cochrane Review is a systematic review of research in health care and health policy.    

The lack of results establishing the capacity of these syrups to fight coughs has led several associations and medical authorities to state their reservations in terms of using these syrups. This is particularly the case among children less than 12 years of age, and for those between 12 and 18 afflicted with respiratory ailments.

Since the fall of 2009, the makers of medicines intended to fight coughs and colds have been obliged to indicate on their labels that their products are not recommended for children under the age of 6. With reason: these children run three times the risk of suffering from side effects than do kids 6 to 12 years of age. In Belgium, many cough medicine brands were pulled from the shelves in 2020.

Negative Effects

In high doses, cough syrup ingredients may even be bad for your health. Dextromethorphan is a hallucinogen that can have serious neurological effects on children. Codeine also exposes coughing children to increased risks of side effects, according to another systematic Cochrane Review carried out in 2016.

Pharmacists warn that cough syrups can pose risks when combined with other medications, like antidepressants. In 2012, two Quebec coroners investigating the deaths of two elderly persons questioned the open sale of most cough syrups. Follow the advice on the label to avoid overdosing. Don’t eve take more than the recommended dosage.

And Honey?

Given the few advantages and the possible disadvantages of cough syrups, perhaps it’s better to stick to an old, tried and true solution: honey. Except for children under a year old, honey seems to be better for treating coughs than is the absence of any treatment, a placebo, or diphenhydramine, concluded another Cochrane Review, this one done in 2018.

Honey seems to have an effect similar to that of dextromethorphan. It also diminishes the length of a coughing fit better than a placebo or salbutamol (Ventolin). But after three days, no treatment seems to work at all, according to this 2018 review. Doctors recommend in all cases that the patient remain hydrated. Consult a physician if the cough persists.

Link to the original article 

Also seen in Reflet de Société No. 32-4, April-May 2024