Synopsis: In a meta-analysis, there was a lack of effectiveness of zinc salt lozenges in reduction of the duration of the common cold.
Source: Jackson JL, et al. Arch Intern Med 1997;157:2373-2376.
Jackson and colleagues conducted a meta-analysis of the zinc salt lozenges and the common cold. After doing multiple literature searches of English language literature and finding 222 citations, they limited the number of articles to 19. They then found nine clinical trials treating adults with zinc salt lozenges. One used zinc gluconate palatability rather than effectiveness against the common cold. Two were excluded for using significantly different study design.
Of the six remaining studies, Jackson et al evaluated each one in a detailed fashion and compared the age of participants, zinc lozenge vs. placebo, the type of zinc formulation used, and the frequency or dose. They found that a summary odds ratio for the incidence of any cold symptoms at one week was 0.50. With the pooled data, compared to a placebo, there was no difference or a 50-50 chance that a symptom would be present regardless of the therapy. They then re-analyzed the data and changed their model assumptions by excluding or including a different piece of information. This is the technique of sensitivity analysis that challenges the meta-analysis: If one of the data points was an outline, would it be possible to change the results? Using three of these, they found that their results were not modified. Their meta-analysis of the randomized trials using zinc salt lozenges in the common cold showed no benefit in reducing the duration of the common cold symptomatology.
COMMENT BY LEN SCARPINATO, DO
The oldest adage regarding the common cold is that it lasts seven days with treatment or a week without. This study essentially backs up that statement. It is ironic that the zinc salt companies are making a significant profit from these products. In the first nine months of 1996, one of the companies sold $900,000 worth of one of their products. This was buoyed by an Annals of Internal Medicine article showing a reduction in coughing, headaches, hoarseness, and sore throats with a zinc lozenge. The stock share tripled in that time periodno surprise there.
Theoretically, the zinc lozenges would not have an effect because they are dissolved in the mouth and the symptoms are mostly nasal. But, some in vitro data point to an effect. Another interesting aspect of this whole discussion is that zinc lozenges taste lousy. I am reminded of the old general practitioners’ saying that the medicine needs to taste as bad as possible for people to believe that it is working. Thus, maybe the effect of a bad-tasting medicine is stronger than a placebo. For my money, I am not prescribing zinc salt lozenges for the common cold, nor will I be taking them for my own colds.
Gemfibrozil treatment of post-CABG patients with isolated low HDL has been associated with marked reduction in subsequent clinical events despite lack of any demonstrated angiographic benefit.
In a recent meta-analysis, Jackson and colleagues found that:
a. zinc salt lozenges reduced the duration of cold symptoms by three days compared to placebo.
b. zinc salt lozenges prolonged the duration of cold symptoms by three days compared to placebo.
c. patients randomized to zinc salt lozenges refused to take them because of unpalatability.
d. regardless of the therapy, there was no difference in the chance that a cold symptom would be present.
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