If the assessment of Godfrey and co-workers that colds first treated on their first day have a "total average duration" (in actuality a half-life) of 5.3 days, the half-life must be compared with the historical 7 day half-life of colds, not the 9.2 day average duration figure used in the Godfrey and co-workers report. Therefore, the reduction in half-live was only 1.7 days. If the half-life is divided by the natural log of 2 to give the average reduction in duration of exponentially decaying colds, the result is 2.5 days. However, this method of analysis is inaccurate for these non-exponential decay curves.

The most accurate conclusions are one-half of the ZGG-treated colds ended 1.2 to 1.7 days before normal, and ZGG-treated patients fared better with essentially all colds being absent after seven days of treatment with ZGG when treatment was started on the first day of their colds.

The stability constants for zinc glycinate complexes are relatively high; for example, log K₁ = 4.8 at 37°C.(44) With a 10-mole excess of glycine at the published salivary pH of 5.0, available Zn²⁺ ion concentration is 20 percent, but it falls rapidly to zero at pH 6.4; and only neutrally and negatively charged zinc glycinate and hydroxide species exist at physiological pH 7.4 and above as shown in Figure 18.

Because Zn²⁺ ions, ZGG, and tannic acid are each astringent in saliva, late-occurring efficacy noticed in the zinc gluconate-glycine report for ZGG lozenges is most likely attributable to astringency. The action appears not from antirhinoviral action of Zn²⁺ ions at physiologic pH 7.4, as no Zn²⁺ ions are available according to Berthon (see Figure 18).

Any possible Zn²⁺ ion action on rhinoviruses should occur during the first few days of a cold when rhinoviruses are present, yet no reduction in duration of colds was noted in this study during those early days. In fact, the frequencies of nasal symptoms were the least affected by ZGG lozenges. Effects on individual symptoms during the early phase also were likely to have been caused by astringency, and not Zn²⁺ ions. Late activity in a cold -- when viruses are essentially absent -- suggests the effect on duration is most likely caused by local astringency, a drying action. This action most likely would not include significant prevention of release of histamine from mast cells considering molecular stabilities.

In this anomaly from the ZIA - day reduction trend, ZIA is unquestionably negative from lack of Zn²⁺ ions, the presence of neutrally (85%) and negatively (15%) charged zinc glycine species, and glycine in excess at pH 7.4. However, no ZIA data-point can be determined as the results do not fall into the quadrant used to estimate ZIA values for other lozenges having negative ZIA values. This anomaly results in a horizontal line to the left of the origin at a positive 1.27 days.