Two randomized controlled trials of zinc gluconate lozenge therapy of experimentally induced rhinovirus colds

Abstract

The therapeutic efficacy of zinc gluconate lozenge therapy in experimentally induced rhinovirus infection was assessed in two randomized controlled trials in susceptible adult volunteers. In trial 1, lozenges containing either zinc gluconate (23 mg of elemental zinc) or placebo were given 36 h after nasal inoculation of rhinovirus type 39 and administered eight times per day for 5 days. All of the volunteers had early cold symptoms at the time that treatment was begun. In trial 2, the same lozenge regimen was used, beginning 2 h after nasal inoculation with rhinovirus type 13, and continued for 7 days. Zinc therapy did not reduce the severity, or duration of cold symptoms or the frequency or duration of viral shedding in either trial. Viral titers were measured in trial 2 and were shown to be unaffected by zinc therapy. Nasal mucus weights and the numbers of paper tissues used were slightly higher in zinc recipients. A statistically significant increase in levels of zinc in serum was documented in zinc recipients after 5 days of therapy. These data suggest that zinc gluconate lozenge therapy is not therapeutically useful in the treatment of rhinovirus colds.

Zinc Gluconate and the Common Cold: A Controlled Clinical Study

“…Even with the recognition that placebo in the present study was not entirely devoid of activity, there was a significant (P< 0.025) reduction in the severity of symptoms in the ZGG treatment group compared with placebo at day 7; day 7 has been commonly used for comparison in other published studies that include duration and symptom severity data. 1,2,15 The effects observed in the present study indicate that there may be a 1 -2 day 'window of opportunity' for treatment with ZGG before the common cold takes hold. It could be determined from further studies whether cold symptoms would last an even shorter time if ZGG treatment were begun on the day of symptom onset.…”

“…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. 6 If the presence of zinc ions in the mouth is required for an effect on the common cold, chelation of zinc may be the reason why the subsequent studies were unsuccessful.…”

“…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.…”

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

“…When we excluded the two trials in which colds were experimentally induced, 24,29 we found no significant change in the number of symptomatic participants at three days and seven days, or in the incidence of any adverse events and nausea. Favours zinc…”

“…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).…”