Zinc for colds? Yes, but don’t swallow whole!

In “Zinc for the common cold—not if, but when” (J Fam Pract. 2011;60:669-671), authors Rao and Rowland state that physicians should “advise patients to start taking zinc supplements (available as tablets, syrup, or lozenges) within 24 hours of the onset of a cold” and imply that zinc tablets can simply be swallowed. They seem to have based their general recommendation on a Cochrane review in which the authors concluded that “zinc administered within 24 hours of onset of symptoms reduces the duration and severity of the common cold in healthy people.”¹

Both the authors of your article and the Cochrane reviewers generalized too far, apparently forgetting that all the common cold treatment studies used zinc lozenges that dissolved slowly in the mouth, rather than (swallowed) zinc tablets or syrups. This is an extremely important difference, because oral dissolution of throat lozenges over a 20- to 30-minute period allows ionic zinc (which has multiple properties of value in treating colds²) to be locally absorbed and transported into the virally infected nose.³ Swallowed tablets offer no such benefit to the nasal tissues.

In the first study of zinc lozenges for common colds, published in 1984,⁴ my colleagues and I showed that it was possible to shorten the duration of colds by 7 days when zinc gluconate tablets (dietary supplements sold over the counter) were slowly dissolved in the mouth every 2 wakeful hours. The reduction in duration, as well as in symptom severity, is highly probable only if the tablets are used as throat lozenges.

Zinc gluconate tablets are available in most pharmacies. However, they have a foul taste and may induce nausea and vomiting. Zinc acetate lozenges that are sold without chelating additives do not have an objectionable taste and may be highly useful in combatting common colds.

George Eby, MS
George Eby Research Institute
Austin, Texas

References

1. Singh M, Das RR. Zinc for the common cold. Cochrane Database Syst Rev. 2011;(2):CD001364.-

2. Eby GA. Zinc lozenges as cure for the common cold—a review and hypothesis. Med Hypotheses. 2010;74:482-492.

3. Sceusa NA, Ehrlich PM. Proof of electro-osmotic drug delivery: a prejudiced clinical trial, delivering from mouth to nose. Drug Deliv Technol. 2008;8:50-59.

4. Eby GA, Davis DR, Halcomb WW. Reduction in duration of common colds by zinc gluconate lozenges in a double-blind study. Antimicrob Agents Chemother. 1984;25:20-24.

The authors respond

We agree that for the treatment of the common cold, zinc needs to be absorbed in the mouth, as is the case with lozenges, rather than swallowed. Currently available zinc preparations marketed for treatment of the common cold are in lozenge, rather than tablet, form.

Goutham Rao, MD
Kate Rowland, MD
Chicago