Background: A previous meta-analysis found that high dose zinc acetate lozenges reduced the duration of common\ncolds by 42%, whereas low zinc doses had no effect. Lozenges are dissolved in the pharyngeal region, thus there might\nbe some difference in the effect of zinc lozenges on the duration of respiratory symptoms in the pharyngeal region\ncompared with the nasal region. The objective of this study was to determine whether zinc acetate lozenges have\ndifferent effects on the duration of common cold symptoms originating from different anatomical regions.\nMethods: We analyzed three randomized trials on zinc acetate lozenges for the common cold administering zinc in\ndoses of 80ââ?¬â??92 mg/day. All three trials reported the effect of zinc on seven respiratory symptoms, and three systemic\nsymptoms. We pooled the effects of zinc lozenges for each symptom and calculated point estimates and 95%\nconfidence intervals (95% CI).\nResults: Zinc acetate lozenges shortened the duration of nasal discharge by 34% (95% CI: 17% to 51%), nasal\ncongestion by 37% (15% to 58%), sneezing by 22% (âË?â??1% to 45%), scratchy throat by 33% (8% to 59%), sore\nthroat by 18% (âË?â??10% to 46%), hoarseness by 43% (3% to 83%), and cough by 46% (28% to 64%). Zinc\nlozenges shortened the duration of muscle ache by 54% (18% to 89%), but there was no difference in the\nduration of headache and fever.\nConclusions: The effect of zinc acetate lozenges on cold symptoms may be associated with the local availability of\nzinc from the lozenges, with the levels being highest in the pharyngeal region. However our findings indicate that the\neffects of zinc ions are not limited to the pharyngeal region. There is no indication that the effect of zinc lozenges on\nnasal symptoms is less than the effect on the symptoms of the pharyngeal region, which is more exposed to released\nzinc ions.\nGiven that the adverse effects of zinc in the three trials were minor, zinc acetate lozenges releasing zinc ions at doses\nof about 80 mg/day may be a useful treatment for the common cold, started within 24 hours, for a time period of less\nthan two weeks.
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