WITHDRAWN: Zinc for the common cold

Abstract

Background: Of the eight trials conducted since 1984 investigating the use of zinc in the treatment of the common cold, four have shown some benefit while the remainder have shown no benefit. Treatment masking and reduced bioavailability of zinc from some formulations have been claimed to influence the results reported. This review was undertaken to assess the overall usefulness of zinc as a treatment for the common cold.

Objectives: Interest in zinc as a treatment for the common cold has grown following the recent publication of several controlled trials. The objective of this review was to assess the effects of zinc lozenges for cold symptoms.

Search strategy: A search was made of the Cochrane Controlled Trials Register, MEDLINE, EMBASE and reference lists of articles. Searches were run to the end of 1997.

Selection criteria: Randomised double blind placebo-controlled trials of zinc for acute upper respiratory tract infection or cold.

Data collection and analysis: Two reviewers independently extracted data and assessed trial quality.

Main results: Seven trials involving 754 cases were included. With the exception of one study, the methodological quality was rated as medium to high. For most outcome measures different summary estimates were used across the studies to describe the duration, incidence and severity of respiratory symptoms. This limited the ability to pool results. Results from two trials (04 - Mossad; 08 - Smith) suggested zinc lozenges reduced the severity and duration of cold symptoms. However, there was significant potential for bias, and further research is required to substantiate these findings. Overall, the results suggest that treatment with zinc lozenges did not reduce the duration of cold symptoms.

Authors' conclusions: Evidence of the effects of zinc lozenges for treating the common cold is inconclusive. Given the potential for treatment to produce side effects, the use of zinc lozenges to treat cold symptoms deserves further study.[This abstract has been prepared centrally.].