Ineffectiveness of zinc gluconate nasal spray and zinc orotate lozenges in common-cold treatment: a double-blind, placebo-controlled clinical trial.

BACKGROUND Zinc gluconate and zinc acetate lozenges have been reported to shorten the duration of common colds in a dose-response manner when the amount of the active ingredient, positively charged zinc ions, is sufficient. OBJECTIVE To improve results using a zinc gluconate nasal spray with zinc orotate lozenges. DESIGN Double-blind, placebo-controlled clinical trial. SETTING Private physician's clinic in Austin, Texas. PARTICIPANTS Seventy-seven volunteers, all of whom had 2 or more signs and symptoms of common colds (with at least 1 nasal symptom) on enrollment in the study. METHODS Zinc gluconate nasal spray (10 mmol) or placebo was used every 15 to 30 minutes, and lozenges were used each several hours to reduce duration and severity of common colds. An intention of treatment was to keep the nasal tissues wet with zinc gluconate solution during wakeful hours. RESULTS After 7 days of treatment, 10 of 16 (63%) zinc-treated patients were asymptomatic compared to 9 of 17 (53%) placebo-treated patients (P = .57). This treatment caused olfactory region pain in some patients and did not reduce the duration or severity of common colds. Treatment did not produce anosmia, which has been reported in other studies following olfactory region administration of ionic zinc in many species and in humans from zinc nasal sprays and gels. CONCLUSION We contend that it is unethical to introduce any potentially permanent anosmia-inducing agent such as zinc or other heavy metals into the interior of the nose in a manner that could result in contact with the olfactory region to treat a temporary discomfort such as a common cold or allergy. We found no reason to recommend intranasal zinc gluconate or zinc orotate lozenges in treating common colds.