Zinc lozenges as cure for the common cold--a review and hypothesis.
Author(s): Eby GA 3rd.
Affiliation(s): Director of Research, George Eby Research Institute, 14909-C Fitzhugh Road,
Austin, TX 78736, USA.
Publication date & source: 2010, Med Hypotheses. , 74(3):482-92
A 7-day reduction in duration of common colds was shown by Eby et al. in 1984
using 23mg zinc gluconate throat lozenges. Over the following 25years, 14
double-blind, placebo-controlled, randomized clinical trials produced widely
differing results with about one-half showing success and the remainder showing
failure. Positively charged, ionic zinc (iZn), but not bound zinc, is strongly
astringent, antirhinoviral, increases interferon-gamma (IFN-gamma) 10-fold,
inhibits intercellular adhesion molecule-1 (ICAM-1) and inhibits the release of
vasoactive ingredients from mast cell granules. Solution equilibrium chemistry
analytical techniques showed lozenge iZn fraction varying from 0% to 100% of
total lozenge zinc between trials, with zinc acetate (ZA) releasing 100% iZn,
zinc gluconate (ZG) releasing 72% iZn and other zinc compounds releasing much
less or none at physiologic pH 7.4. Since only iZn has in vitro benefits, iZn
variations are hypothesized to have produced the widely varying clinical results.
In support of the iZn hypothesis, lozenge iZn and total daily iZn in trials were
found highly correlated with reductions in common cold durations with statistical
significance for mean duration (P<0.001) and median duration (P<0.004), while
total zinc (iZn plus bound) showed no correlation with changes in duration.
Duration reductions (mean 0 days, median 0.43 days) for multi-ligand ZG and ZA
lozenges differed significantly from duration reductions (mean 3.37 days, median
2.9 days) for single ligand ZA and ZG lozenges (P<0.001) showing that additive
ligands as flavor-masks damaged or eliminated efficacy. Five of 6 trials with
lozenges whose zinc compositions had a first stability constant of 1.7 or less
succeeded, while only 2 of 9 trials of lozenges with higher stability succeeded
(P<0.02). From the strong, multiple statistical relationships found, it is
inferred that iZn is the active ingredient in zinc lozenges for colds, as it is
in vitro against rhinoviruses, and that solution chemistry analytical techniques
used at physiological pH are correct means for lozenge iZn analysis. Zinc
lozenges slowly dissolving in the mouth over a 20-30 min period releasing
adequate iZn (18 mg) used each 2h are hypothesized to shorten common colds by 6-7
days, which is a cure for the common cold. Due to inadequate lozenge iZn very few
of more than 40 different brands of zinc lozenges on the US market are expected
to have any effect on the duration or severity of common colds.
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