High dose zinc acetate lozenges shortened the duration of common-cold associated nasal discharge by 34%, nasal congestion by 37%, scratchy throat by 33%, and cough by 46%, according to a meta-analysis.
The common cold is an infection caused by over a hundred viruses, and it is a major cause of days off school or work and visits to a doctor. A previous meta-analysis of three randomized trials found that high dose zinc acetate lozenges shorten the duration of colds by 42%. Since all of the three studies reported the duration of diverse respiratory symptoms and of systemic symptoms such as muscle ache and headache, Harri Hemilä from Helsinki, Finland and Elizabeth Chalker from Sydney, Australia decided to investigate whether there are differences in the effect of zinc lozenges on different common-cold symptoms.
When zinc acetate lozenges dissolve in the mouth, zinc ions are released into the saliva of the pharyngeal region where the levels are consequently high. Therefore the effects of zinc lozenges might be greatest on symptoms of the pharyngeal region such as sore throat, and less on nasal symptoms. However, when Hemilä and Chalker pooled together the results of the three studies, they found no evidence that the effects of zinc lozenges are less for nasal symptoms compared with respiratory symptoms originating from lower anatomical regions.
According to the calculations by Hemilä and Chalker, high dose zinc acetate lozenges shortened the duration of nasal discharge by 34%, nasal congestion by 37%, sneezing by 22%, scratchy throat by 33%, sore throat by 18%, hoarseness by 43%, and cough by 46%. Furthermore, they found strong evidence that zinc lozenges also shortened the duration of muscle ache by 54%. On the other hand, there was no evidence of zinc effect on the duration of headache and fever. However, the latter two symptoms were infrequent in the three studies and therefore no definite conclusions can be drawn on headache and fever.
Adverse effects of zinc were minor in the three studies. Therefore Hemilä and Chalker conclude from their research that "zinc acetate lozenges releasing zinc ions at doses of about 80 mg/day may be a useful treatment for the common cold, started within 24 hours, for a time period of less than two weeks."