Only zinc lozenges releasing Zn²⁺ ions at pH 7.4 have use in reducing the duration of common colds. A linear dose-response relationship exists between nonnegative ZIA values of zinc lozenges and reduction in duration of common colds. Variations in ZIA from different zinc lozenge formulations caused differing results in trials. Differences in lozenge ZIA values provide a reasonable explanation for variations in previous trial results. As found in vitro, Zn²⁺ ions appear to inhibit the replication of rhinoviruses, induce interferon release, and stabilize cell membranes when released by lozenges. A mouth-nose BCEC contributes strongly to the absorption and movement of orally absorbed Zn²⁺ ions into the virally infected tissues of the nose during common colds. The ZIA method of analysis is a valid means of assessing prospective efficacy of experimental zinc lozenges in the reduction in duration of common colds. Additional common cold treatment clinical trials are needed using pleasant-tasting zinc acetate compacts having ZIA values between 50 and 150. (peer review symbol)

Acknowledgment

Special thanks are extended to Guy Berthon, Ph.D., Director of Research CNRS, INSERM Unit-305 Equipe "Bioréactifs: Spéciation et Biodisponibilité", Toulouse, France, for definitive determinations of zinc speciation from several zinc compositions, and for his consistent support of this research.