Zinc Acetate Lozenges May Improve the Recovery Rate of Common Cold Patients: An Individual Patient Data Meta-Analysis

Abstract

Background.A previous meta-analysis of 3 zinc acetate lozenge trials estimated that colds were on average 40% shorter for the zinc groups. However, the duration of colds is a time outcome, and survival analysis may be a more informative approach. The objective of this individual patient data (IPD) meta-analysis was to estimate the effect of zinc acetate lozenges on the rate of recovery from colds.Methods.We analyzed IPD for 3 randomized placebo-controlled trials in which 80–92 mg/day of elemental zinc were administered as zinc acetate lozenges to 199 common cold patients. We used mixed-effects Cox regression to estimate the effect of zinc.Results.Patients administered zinc lozenges recovered faster by rate ratio 3.1 (95% confidence interval, 2.1–4.7). The effect was not modified by age, sex, race, allergy, smoking, or baseline common cold severity. On the 5th day, 70% of the zinc patients had recovered compared with 27% of the placebo patients. Accordingly, 2.6 times more patients were cured in the zinc group. The difference also corresponds to the number needed to treat of 2.3 on the 5th day. None of the studies observed serious adverse effects of zinc.Conclusions.The 3-fold increase in the rate of recovery from the common cold is a clinically important effect. The optimal formulation of zinc lozenges and an ideal frequency of their administration should be examined. Given the evidence of efficacy, common cold patients may be instructed to try zinc acetate lozenges within 24 hours of onset of symptoms.

Zinc acetate lozenges for the treatment of the common cold: a randomised controlled trial

“…At the beginning of our trial, there was no evidence that participants could infer their treatment by looking and tasting their own lozenges. Our sample size calculation was based on the findings of three previous zinc acetate lozenge trials 6–8 20. Thus, we expected positive results.…”

“…We considered that the 5-day treatment should be sufficient to demonstrate an effect of zinc acetate lozenges, since in a meta-analysis of three trials with zinc acetate lozenges, a significant benefit of zinc lozenges was seen within 5 days of treatment 20. We also assumed that the rapid initiation of zinc lozenges might lead to effects that extend beyond the active treatment period.…”

“…Power calculation: based on an assumption that 60% of patients with common cold in the zinc acetate group and 30% in the placebo group would recover by the fifth day,20 42+42 patients with common cold would be sufficient to reach an 80% power to detect a difference between the trial groups with p<0.05. In our protocol, we erroneously calculated 23 participants per group as the sample size.…”

“…Meta-analyses of three zinc acetate studies6–8 with a total of 199 patients with common cold found that recovery rate was increased threefold20 and colds were shortened on average by 3 days and 36% 21. Zinc gluconate lozenges have been suggested to be less effective than zinc acetate lozenges,16 but a meta-analysis of seven trials with a total of 575 common cold participants did not find significant difference between lozenges composed of the two salts 19.…”

“…Nevertheless, despite certain promising findings, the status of zinc lozenges as a treatment option for the common cold is still uncertain, and they are not currently recommended for the treatment of the common cold in guidelines 22 23. Although several meta-analyses suggest that zinc lozenges may have the potential to shorten colds,16 18–21 the findings from trials are heterogeneous indicating that further research is needed to determine the conditions when zinc lozenges are effective and the type and dosage of lozenges that are optimal.…”