Histamine as a ligand in blood plasma. Part 7. Malate, malonate, maleate and tartrate as adjuvants of zinc to favour histamine tissue diffusion through mixed-ligand coordination. In vitro tests on lymphocyte proliferation

Linearity in Dose—Response from Zinc Lozenges in Treatment of Common Colds

Objective:

To test the hypothesis that major variations in daily zinc ion availability (ZIA) between lozenge formulations caused greatly differing results and to describe the biologically closed electric circuit between the mouth and nose.

Data Sources:

Data sources included clinical and in vitro reports, zinc speciation computations, and unpublished data from the original researchers and manufacturers.

Data Extraction:

Data were extracted to determine the composition and usage of lozenges and resultant changes in common cold duration. Lozenge ZIA values were determined from Zn2+ ion concentrations and oral contact time.

Data Synthesis:

Data synthesis disclosed that lozenges releasing Zn2+ ions at physiologic pH (positive ZIA values) shortened the duration of colds. Conversely, lozenges that released negatively charged zinc complexes (ZnLN−) at physiologic pH (negative ZIA values) lengthened the duration of colds. ZIA 100 lozenges reduced the duration of colds by 7 days. ZIA 0 lozenges had no effect. ZIA −55 lozenges lengthened the duration of colds by 4.4 days.

Conclusions:

The hypothesis is valid that major variations in ZIA from different zinc lozenge formulations used in clinical trials caused greatly differing results. A linear dose-response relationship exists between ZIA values of zinc lozenges and changes in duration of common colds. In agreement with in vitro activity, Zn2+ ions from lozenges inhibit replication of rhinoviruses, induce interferon release, and stabilize cell membranes in common cold treatment. Linearity in dose-response shows efficacy against common cold duration from clinically untested lozenges to be predictable on the basis of readily determined ZIA values of experimental lozenges.

Ab initio calculation of the Zn isotope effect in phosphates, citrates, and malates and applications to plants and soil

Stable Zn isotopes are fractionated in roots and leaves of plants. Analyses demonstrate that the heavy Zn isotopes are enriched in the root system of plants with respect to shoots and leaves as well as the host soil, but the fractionation mechanisms remain unclear. Here we show that the origin of this isotope fractionation is due to a chemical isotope effect upon complexation by Zn malates and citrates in the aerial parts and by phosphates in the roots. We calculated the Zn isotope effect in aqueous citrates, malates, and phosphates by ab initio methods. For pH<5, the Zn isotopic compositions of the various parts of the plants are expected to be similar to those of groundwater. In the neutral to alkaline region, the calculations correctly predict that (66)Zn is enriched over (64)Zn in roots, which concentrate phosphates, with respect to leaves, which concentrate malates and citrates, by about one permil. It is proposed that Zn isotope fractionation represents a useful tracer of Zn availability and mobility in soils.

Zinc lozenges as cure for the common cold--a review and hypothesis

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.

Zinc lozenges: cold cure or candy? Solution chemistry determinations

Common colds were shortened by 7 days in a 1984 clinical trial using zinc gluconate throat lozenges each 2 h. Between then and 2004, 10 other double-blind, placebo-controlled clinical trials showed widely varying results. This re-analysis of these trials presents solution chemistry methods to elucidate differences in efficacy. Statistically significant correlation was shown between total daily dosages of positively charged zinc species and reductions in median (p = 0.005) and mean duration (p < 0.02) of common colds in these trials.

The role of zinc lozenges in treatment of the common cold

OBJECTIVE

To summarize and critique the medical literature on the use of zinc lozenges for treatment of the common cold.

DATA SOURCES

MEDLINE searches (January 1966-June 1997) identified human clinical trials on the use of zinc lozenges for the treatment of the common cold. Bibliographies were also reviewed for relevant articles.

STUDY SELECTION

Double-blind, placebo-controlled trials of zinc lozenges in adults for the treatment of the common cold, with the clinical end points of reduction in duration and/or severity of cold symptoms.

DATA EXTRACTION

All double-blind placebo-controlled, human clinical trials on the use of zinc lozenges for the treatment of the common cold were included.

DATA SYNTHESIS

The use of zinc lozenges in the treatment of the common cold has been suggested to reduce the duration and severity of cold symptoms. Of eight double-blind, placebo-controlled trials, four found zinc lozenges to be effective, while the other four reported no difference between zinc and placebo therapy. Potential reasons for the discrepancy between the results of these trials include inadequate placebo control, formulation of the lozenge, and the dose of zinc used. Common adverse effects include unpleasant taste, mouth irritation, and nausea.

CONCLUSIONS

Treatment of the common cold with zinc gluconate lozenges, using adequate doses of elemental zinc, may be effective in reducing duration and severity of cold symptoms. The benefit appears to be maximal if the lozenges are started immediately after the onset of symptoms. The formulation of the lozenges also appears to be important because the addition of citric acid or tartaric acid may reduce efficacy due to chelation of zinc ion. Although zinc gluconate lozenges have dominated clinical trials thus far, further studies are needed to demonstrate the efficacy of zinc acetate lozenges and to determine whether their adverse effect profile is more favorable to that of zinc gluconate lozenges. Patients should play an important role in the decision-making process and must decide whether the benefit gained from treatment with zinc lozenges outweighs the potential adverse effects.