PID1: EFFICACY OF ZINC LOZENGES ON THE DURATION OF COMMON COLD SYMPTOMS: A META-ANALYSIS REVISITED

Abstract

OBJECTIVE: Cold symptoms are both common and costly. The effectiveness of zinc lozenges in reducing the duration of common cold symptoms has been investigated in several studies with discrepant results. We therefore performed a meta-analysis in an attempt to clarify these discrepancies and determine the overall effectiveness of zinc lozenges in the treatment of the common cold. METHODS: A computerized search of the MEDLINE database from January 1966 to December 2000 was performed to identify randomized controlled trials comparing zinc lozenges to placebo for the common cold. Data were systematically abstracted. The outcome assessed was the duration of cold symptoms. Quantitative pooling was undertaken using the Dersimonian and Laird random-effects model. RESULTS: Five studies met the inclusion criteria and provided sufficient information to calculate the mean duration of cold symptoms. A total of 562 subjects were included in these trials: 283 in the zinc group and 279 in the placebo group. The summary mean duration of cold symptoms in the zinc group was 2.25 days less than that in the placebo group (95% confidence interval [CI], 1.07–3.43). However, there was evidence of statistical heterogeneity among studies (P = 0.003). In a subgroup analysis, we found that there were two sets of homogeneous studies with different magnitudes of reduction: 3.6 days (95% CI: 2.77,4.43) and 1.32 days (95% CI: 0.52,2.13). CONCLUSIONS: Zinc lozenges appear to be an effective treatment for reducing the duration of cold symptoms. However, further analyses are required to explore the sources of heterogeneity. A formal cost-effectiveness analysis may be necessary to determine whether this intervention is economical.