30 Jan Do Zinc Lozenges Really Help the Common Cold?
MedicalResearch.com Interview with:
Harri Hemilä, MD, PhD
Department of Public Health
University of Helsinki, Finland
MedicalResearch.com: What is the background for this study?
Response: Eight previous randomized trials reported that zinc lozenges can shorten and alleviate the common cold, when zinc doses were over 80 mg/day. There are also several negative findings from other trials, but those can be explained by low doses of zinc and by substances in lozenges that bind zinc so that free zinc is not released to the oro-pharyneal region. For example, citric acid binds zinc ions very strongly and has been a component of some previous lozenges.
In our trial, common cold patients were instructed to use 6 commercially available zinc lozenges, 78 mg/day of zinc, for 5 days as sson as feasible after the start of the common cold.
MedicalResearch.com: What are the main findings?
Response: Over the 5-day treatment, there was no difference in the recovery rate between zinc and placebo groups.
However, after the 5-day treatment patients in the zinc group recovered significantly more slowly than in the placebo group. This may be explained by the rebound effect so that stopping a treatment causes effect in the harmful direction. Although this finding is consistent with pharmacological effect of zinc, it does not justify the use of the trial lozenge for treating colds.
MedicalResearch.com: What should readers take away from your report?
Response: Many pharmacological treatments are quite simple in such a respect that we are only interested in the dose of the drug and we assume that the drug is effectively absorbed from the intestines. However, zinc lozenges can vary technically and those on the market do vary very much. A poorly composed lozenge does not release free zinc even if the dose per lozenge might be reasonable. Although the 8 previous trials demonstrate that properly composed zinc lozenges can shorten colds, an ordinary common cold patient cannot know whether a particular lozenge on the market is effective or useless.
MedicalResearch.com: What recommendations do you have for future research as a result of this work?
Response: Based on our negative findings with our lozenge and protocol, in future trial the lozenges should be more slowly dissolving in mouth, the dose of zinc should be over 92 mg/day and the treatment should last longer than 5 days. The characteristics of zinc lozenges that are suggested to be clinically efficacious should be evaluated in detail before they can be widely promoted for common cold treatment.
MedicalResearch.com: Is there anything else you would like to add?
Response: Our trial does not refute the previously published 8 trials with positive results. However, our trial shows that more research is needed to figure out what kinds of zinc lozenges are effective before they can be widely proposed for common cold treatment. What is the dose of zinc per lozenge and how should the lozenges been composed, and how many times per day and for how long should they be taken?
Any disclosures? We received the zinc lozenges and their placebos from a local drug company, but that company was not involved in any way in our planning of the trial or in the analysis of the results. We informed the company of our results only after the trial report was published.
Hemilä H, Haukka J, Alho M, et al
Zinc acetate lozenges for the treatment of the common cold: a randomised controlled trial
BMJ Open 2020;10:e031662. doi: 10.1136/bmjopen-2019-031662
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