Objective To examine a commercially available zinc acetate lozenge for treating the common cold.
Design Randomised, double-blinded, placebo-controlled trial.
Setting Working population in Finland.
Participants We included men and women aged ≥18 years who usually had ≥1 cold per winter. Exclusions were pregnancy, lactation, chronic runny nose or chronic cough.
Intervention We randomised 253 participants to receive a package of lozenges to be taken if they caught the common cold. Of the 253 participants, 88 contracted the common cold and 87 were included in our primary analysis. Zinc acetate lozenges contained 13 mg elemental zinc and placebo lozenges contained sucrose octa-acetate to camouflage the taste of zinc. Instruction to use was six times per day for the maximum of 5 days.
Primary outcome Rate of recovery from the common cold analysed by Cox regression.
Results There was no difference in the recovery rate between zinc and placebo participants during the 10-day follow-up (rate ratio for zinc vs placebo=0.68, 95% CI 0.42 to 1.08; p=0.10). The recovery rate for the two groups was similar during the 5-day intervention, but for 2 days after the end of zinc/placebo use, the zinc participants recovered significantly slower compared with the placebo participants (p=0.003). In the zinc group, 37% did not report adverse effects, the corresponding proportion being 69% in the placebo group.
Conclusions A commercially available zinc acetate lozenge was not effective in treating the common cold when instructed to be used for 5 days after the first symptoms. Taste has been a common problem in previous zinc lozenge trials, but a third of zinc participants did not complain of any adverse effects. More research is needed to evaluate the characteristics of zinc lozenges that may be clinically efficacious before zinc lozenges can be widely promoted for common cold treatment.
Trial registration number NCT03309995.
- common cold
- randomised trial
- respiratory infections
- zinc lozenges
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Contributors HH conceived and designed the study, coordinated the trial, prepared the first draft of the manuscript and was responsible for the final manuscript. HH, JH, MA, JV and MK developed the protocol. HH and MA recruited the patients and acquired the data. HH did the statistical analysis. HH, JH and MK analysed and interpreted the data. All authors revised manuscript drafts, approved the final manuscript and contributed intellectually important content. HH is the guarantor of the paper and takes responsibility for the integrity of the work as a whole, from inception to published article.
Funding This study was investigator-initiated trial, which was supported by NordForsk (75021) and Academy of Finland (311492). Zinc and placebo lozenges were donated by the University Pharmacy, Helsinki, Finland.
Disclaimer However, University Pharmacy had no role in planning and conducting the trial or in the interpretation of findings and the writing of the manuscript.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval The Ethics Committee of Helsinki University Central Hospital approved the trial (HUS/2439/2017).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.