Alert parents know that small children should not take over-the-counter cough medications. Now researchers say the stuff might not help adults much, either.

Over-the-counter medicine is commonly and casually used by millions of cold sufferers every year, but there is no good evidence for or against the effectiveness of OTC cough medicines, concludes a new systematic review of studies.

“I do not give my kids over-the-counter cough medicine,” said Thomas Fahey, professor of general practice at the Royal College of Surgeons in Ireland Medical School and review co-author. “I do not advise my patients to do so.”

In their review, Fahey and colleagues looked at both children- and adult-focused studies. Some reported that OTC cough medicines helped patients; others said they did not. With conflicting evidence, the various studies presented a non-cohesive picture.

Another issue concerned the researchers, who wrote, “six out of the nine studies that were supported by the pharmaceutical industry showed positive results compared to three positive studies out of 16 trials that did not report any conflict of interest.”

On the other hand, “Most preparations appear to be safe based on those studies reporting side effects, which only described a low incidence of mainly minor adverse effects,” the researchers found.

The review of the studies appears in the latest issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews like this one draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.

The Cochrane review encompassed 25 studies, 17 of which involved 2,876 adults and eight of which involved 616 children.

In the adult studies, six compared antitussives medicines used to relieve coughs, such as Robitussin, with placebo and had variable results. Two studies compared an expectorant such as Mucinex, which promotes the discharge of mucus from the respiratory tract, with placebo; one found benefits. Another two studies focusing on combinations of antihistamine and decongestants, produced conflicting results, while three studies found antihistamines were no more effective than placebo in relieving cough.

Three other adult studies compared combinations of drugs with placebo and showed some benefit in reducing cough; one study found that mucolytics, which break down mucus, reduced cough frequency.

In studies involving children, seven — two with antitussives, two with antihistamines, two with antihistamine decongestants and one with antitussive-bronchodilator combinations — showed the drugs were no more effective than placebo. (Bronchodilators work to ease coughs by widening air passages.)

In another study of two pediatric cough syrups, Triaminicol and Dacol, both showed “satisfactory” response compared to placebo medicines.

The duration of drug therapy varied from “a single dose treatment to an 18-day course,” the authors wrote. “For example, five studies testing antitussives used short-term cough relief after a single dose as an outcome…whereas more relevant outcomes for patients would be the effect after one day, three days or a week.”

Because of the variations, there were no broad statistical conclusions. “It wasn’t appropriate to pool the data,” Fahey said.

During the past decade, physicians have increasingly voiced concerns about these medicines and the potential for overdosing young children. In August, the U.S. Food and Drug Administration warned parents not to give over-the-counter cough and cold remedies to children under 2 years old without a doctor’s approval. During a hearing before an FDA panel in October, federal health advisers said that children younger than six years should not take the medicines.

But is it even necessary to cure a cough?

People often worry about a cough if it has not gone away after a week, Fahey said. Actually, the duration of a cough is commonly two weeks in children and three weeks in adults.

“I think there’s the laymen’s perception,” Fahey said. The common conclusion is that “something should be done about it. It [coughing] is troublesome at night. But it is not a bad thing to be coughing. It could be helpful. It is a mechanism for shedding viruses.” 

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