Lack of knowledge of the availability of Zn2+ ions by both the authors of the following studies and the independent manufacturers of lozenges used in the authors' studies has seriously impeded clinical research involving lozenges releasing Zn2+ ions as treatment and cure for the common cold. Some clinical researchers, not knowing the lozenges supplied by manufacturers contributed few or no Zn2+ ions, came to believe "zinc didn't work."
The purpose of the following reviews of the clinical studies is to bring to light the amount of Zn2+ ions available from study lozenges (ZIA values of treatments) and to compare those values with the reduction in duration in common colds.
Using this approach, it becomes obvious that total Zn2+ ions -- and not total zinc compounds -- are effective in reducing the duration of common colds. It will also be shown the amount of reduction in duration is directly related to the amount of Zn2+ ions available as calculated using ZIA values, reflecting Fick's laws. Salivary Zn2+ ion concentrations throughout the following reviews are given at pH 7.4, unless otherwise indicated, and should be interpreted as initial concentrations or maximums, as some Zn2+ ions bind with salivary proteins and some are absorbed into tissues.
Each of the following reports was analyzed using published data, lozenge samples from the studies, manufacturers' formulas for the lozenges used in the studies, and replicated lozenges based upon the manufacturer's descriptions to determine ZIA, half-lives, and changes in duration. All data are supported by the original sources. Confirmation of the lozenge ingredients and manufacturing procedures can be obtained from the original cited sources.
Every possible effort was made to report the findings of the researchers accurately, to discover exactly how lozenges were made, to discover how lozenges were actually used, and to discover the ingredients and their amounts present in the lozenges.
Every possible effort was expended to assess accurately the differences in the reported results caused by variation in the procedures and actual chemistry of the lozenges used in clinical trials.