The effectiveness of high dose zinc acetate lozenges on various common cold symptoms: a meta-analysis.
Level 1 - systematic review of randomized trials
Meta-analysis of randomized controlled trials
PubMed 25888289 · doi:10.1186/s12875-015-0237-6
What was done
Meta-analysis of three randomized controlled trials evaluating high-dose zinc acetate lozenges (80–92 mg/day of elemental zinc) for the common cold. The authors pooled effect sizes and calculated 95% confidence intervals for the duration of seven respiratory symptoms (nasal discharge, nasal congestion, sneezing, scratchy throat, sore throat, hoarseness, and cough) and three systemic symptoms (muscle ache, headache, and fever) to examine if efficacy differed by anatomical region.
What was found
Zinc acetate lozenges significantly shortened the duration of nasal discharge by 34% (95% CI: 17% to 51%), nasal congestion by 37% (95% CI: 15% to 58%), scratchy throat by 33% (95% CI: 8% to 59%), hoarseness by 43% (95% CI: 3% to 83%), cough by 46% (95% CI: 28% to 64%), and muscle ache by 54% (95% CI: 18% to 89%). Reductions in sneezing (22%, 95% CI: -1% to 45%) and sore throat (18%, 95% CI: -10% to 46%) crossed zero. No difference was observed for headache or fever.
Why it matters
The findings show that lozenge-delivered zinc ions reduce the duration of nasal and systemic symptoms to a similar degree as pharyngeal symptoms, indicating therapeutic benefit is not confined to the pharynx where the lozenge dissolves.
Limits
The analysis is restricted to only three trials, and total participant counts are not reported in the abstract. Several symptom estimates had wide confidence intervals, and adverse event reporting in the abstract was qualitative only.
Cited by
- supports Short-term high-dose zinc supplementation of about 80 mg per day lessens respiratory illness symptoms and shortens disease duration.