Failure of zinc gluconate in treatment of acute upper respiratory tract infections

Abstract

Zinc is a trace metal with in vitro activity against rhinovirus, the major etiologic agent in acute upper respiratory tract infections (URIs). A previous trial of zinc gluconate supported its efficacy in treating URIs, but the effectiveness of blinding was uncertain. We conducted a prospective randomized trial of zinc gluconate versus a taste-matched placebo of sucrose octaacetate. Lozenges containing either 23 mg of elemental zinc or placebo were taken every 2 h. Eleven URI symptoms were rated daily on a scale of 0 (not present) to 3 (severe). Duration of illness, reflected in the proportion of subjects remaining symptomatic on each day, was not significantly reduced (maximum difference of 12.6% on day 7, P = 0.09; 95% confidence interval, -6 to 31%) by either treatment. Severity of illness, assessed by using a summed severity score, was reduced incrementally by 7 to 8% on days 5 to 7 (P = 0.02) in subjects taking zinc. Adverse effects, mostly nausea and altered taste, were reported by 50% of subjects taking zinc. We conclude that while zinc gluconate may produce a small reduction in overall severity of symptoms, this is not clinically significant. Given the additional high incidence of adverse effects, zinc gluconate cannot be recommended for use in the treatment of acute URIs.

Zinc for the treatment of the common cold: a systematic review and meta-analysis of randomized controlled trials

“…The method of randomization was not reported in two trials. 28,38 The remaining six trials had low risk of bias. Sensitivity analysis excluding the trials with high risk of bias did not change the results, so the evidence was not downgraded.…”

“…The remaining four trials either measured but did not report the outcome 26,29 or reported the proportion of symptomatic patients on each day. 38,39 Eight trials (n = 934) could be pooled in the meta-analysis ( Figure 2). All trials involved patients with naturally acquired colds.…”

“…p No serious design limitations: Three trials had significant design concerns. 28,29[B], 38 All had incomplete outcome data and unclear allocation concealment. The method of randomization was not reported in two trials.…”

Zinc Gluconate and the Common Cold: A Controlled Clinical Study

“…Attempts made to duplicate the success which Eby et al 1 had in 1984 in reducing the duration of the common cold using zinc gluconate have generally been disappointing, [2][3][4] the probable reason being that zinc gluconate was inactivated by additives used to mask its unpleasant taste. It has been demonstrated that of these agents, e.g.…”

“…It has been demonstrated that of these agents, e.g. citric acid, 2 tartaric acid, 3 or mannitol/sorbitol, 4 inactivate zinc by chelation in saliva. 5,6 Unflavoured zinc gluconate and the zinc gluconate -glycine (ZGG) lozenges used in the present study release 90 -93% of zinc ions, 6 whereas citric acid 2 and mannitol/sorbitol 4 formulations release no zinc ions when dissolved in the mouth.…”