LETTER
Where's the Bias?
George Eby, MS
1 January 1998 | Volume 128 Issue 1 | Page 75
TO THE EDITOR:
In my opinion, the main source of bias in the use of zinc lozenges for the common cold has come from Dr. Jack M. Gwaltney Jr., the U.S. Food and Drug Administration's chief common cold consultant. He has consistently denied the efficacy of zinc lozenges since publication of our original 1984 article [1].
Gwaltney and colleagues later published a study comparing lozenges containing zinc gluconate and 1.3-mole citric acid with placebo [2]. The citric acid bound all zinc ions and released negatively charged zinc species at a physiologic pH [3]. Those lozenges worsened colds. These results convinced Dr. Gwaltney and others to believe that all zinc lozenges are nonefficacious. Interestingly, Dr. Gwaltney has three recent U.S. patents (5,492,689; 5,422,097; and 5,240,694) on common cold treatment. Among the appropriate antiviral agents listed in his patents are "zinc salts." I wonder whether ownership of these patents permits him to continue to be an unbiased authority on the common cold.
From Dr. Gwaltney's research, it is reasonable to expect that negatively charged zinc species from commercial zinc gluconate-citrate or zinc-citrate lozenges would bind native zinc ions from the oral and nasal tissues. This activity would worsen colds and possibly cause sequelae. On the other hand, the Cold-Eeze zinc gluconate-glycine lozenges studied by Mossad and colleagues [4] release positively charged zinc ions. Given the availability of the zinc ion, it is not surprising that these lozenges, when used as directed or used with increased frequency, would reduce the duration and severity of colds. Commercially available zinc acetate lozenges release all of their zinc as positively charged zinc ions at a physiologic pH of 7.4. The effect of these lozenges on the duration and severity of colds is being studied in clinical trials [5].
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Author and Article Information
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George Eby Research; Austin, TX 78704
1. 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; 25:20-4.
2. Farr BM, Conner EM, Betts RF. Two randomized controlled trials of zinc gluconate lozenge therapy of experimentally induced rhinovirus colds. Antimicrob Agents Chemother. 1987; 31:1183-7.
3. Martin RB. pH as a variable in free zinc ion concentration from zinc-containing lozenges [Letter]. Antimicrob Agents Chemother. 1988; 32:608-9.
4. Mossad SB, Macknin ML, Medendorp SV, Mason P. Zinc gluconate lozenges for treating the common cold. A randomized, double-blind, placebo-controlled study. Ann Intern Med. 1996; 125:81-8.
5. Eby GA. Zinc lozenges as cure for common colds. Ann Pharmacother. 1996; 30:1336-8.
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