Check out the contents of any medicine cabinet and you're likely to find at least one bottle of cough syrup. But do these commonly used drugs actually work?
Maybe not as well as we'd like to think, British researchers say.
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Medicines no more effective than placebo
In an analysis of 15 studies that compared over-the-counter cough medications to a placebo, University of Bristol scientists report that, in most cases, the cough preparations were no more effective than the fake drug.
"There's very little evidence for or against the effectiveness of these medicines," says Dr. Knut Schroeder, one of the study's authors and a medical research counsel training fellow at the University of Bristol in the United Kingdom.
Pharmaceutical companies disagree
Not surprisingly, Procter & Gamble, the maker of such leading brands as Vick's 44 and NyQuil, disagrees.
"We feel our products work very well and have a long history," says Kurt Weingand, a principal clinical scientist in the Procter & Gamble Health Sciences Institute.
In fact, Weingand adds, P&G recently published a study in the journal Chest that found a 30-milligram dose of dextromethorphan (an active ingredient in NyQuil) was effective for treating cough when compared to a placebo.
No one at Whitehall-Robins, the maker of Robitussin cough medications, was available for comment.
Clinical results disagree
In the latest study, Schroeder and his colleagues examined data from 15 different studies involving a total of 2,166 adult participants who were between 23 and 48 years old. The studies had to include people with an acute cough, meaning that they had not had the cough for more than three weeks, and the cough could not have been artificially induced with chemicals.
In most of the studies, the participants kept diaries of their cough symptoms.
The various studies tested antitussive medications, expectorants, antihistamines, antihistamine-decongestant combinations, and other combinations of medications.
Active ingredients in the antitussive medications were codeine, moguisteine or dextromethorphan. Guaifenesin, which is found in Robitussin and other brands, was the active ingredient in expectorants.
The antihistamine studied was loratadine, an active ingredient in Allegra, Claritin, and the allergy medicines Dimetapp and Contac. In the antihistamine-decongestant combinations dexbrompheniramine or pseudoephedrine (sold under such brand names as Dimetapp or Sudafed) was combined with guaifenesin.
And, in the other combinations category, antitussive medication was combined with ingredients like ephedrine, menthol or eucalyptus.
In nine of the 15 studies, Schroeder says the active treatment was no better than the placebo. For the other six trials, the results varied, but Schroeder says he doubts the results are clinically meaningful.
More trials needed
Antihistamines were found to be no more effective in treating cough than a placebo. In the antitussive group, there was little difference between the cough preparations and the placebo, though several of the studies did report a slight edge for the medication.
In the expectorant category, one study found that 75 percent of those receiving medication reported relief of symptoms while only 31 percent in the placebo group did. But another study on expectorant medications found very little difference between the medication and the placebo. The other groups of medications all had similarly conflicting studies.
"We need more evidence from properly conducted trials," concludes Schroeder.
No side-effects reported
In the meantime, Schroeder adds, since no evidence of any serious side effects showed up in the studies, it's OK for individuals to use cough medicines.
However, the researchers don't believe that there should be broad recommendations for using these medications by groups like the National Health System in the UK, until more studies are done.
"Some people might find them helpful on an individual level," Schroeder says. "But they may be an unnecessary expense."
Results of the study appear in the February 9 issue of the British Medical Journal.
Results should be interpreted cautiously
Schroeder acknowledges that there were some limitations to this analysis and says the results should be interpreted with caution. First, the researchers were comparing different studies that used different methods. Also, many of the individual studies were small in size.
Dr Wei-Nchih Lee, an assistant professor of medicine from New York Medical College in Valhalla, says the authors did a good job making their point: that it's important to know that there are clear benefits to a medication before making any public policy recommendations.
"The authors are not saying that OTC medications are not beneficial," says Lee. "Clinicians can make up their own minds, but this shouldn't be public policy."
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