Oral Zinc May Cut Colds Length

Oral zinc formulations appear to shorten the duration of adult cold symptoms but mild adverse effects are common according to a metaanalysis

Based on an evaluation of 17 trials people who received zinc had a shorter duration of cold symptoms compared with patients given placebo mean difference 8722165 days 95 CI 8722250 to 8722081 Michelle Science MD from The Hospital for Sick Children in Toronto and colleagues wrote online in CMAJ

However heterogeneity among the studies was high I295 Science and colleagues cautioned We found that orally administered zinc shortened the duration of cold symptoms wrote McMaster University in Hamilton Ontario Canada These findings however are tempered by significant heterogeneity and quality of evidence

The randomized controlled trials included 2121 participants between ages 1 and 65 the purpose of the trials was to determine the efficacy and safety of oral zinc in treating the common cold The studies primary outcomes were the duration of cold symptoms

Secondary outcomes included the severity of cold symptoms the presence of symptoms after 3 and 7 days and adverse events Heterogeneity was evaluated using the I2 statistic and when I2 reached 880540 subgroup analyses were performed

Treatment regimens included

Zinc gluconate lozenges 8 trials or tablets 1
Zinc acetate lozenges 4
Zinc sulfate syrup 2 and either
Zinc gluconate or zinc acetate 2 compared with placebo
The authors reported duration of treatment was different in all trials range 314 days or until symptom resolution Overall they found that zinc shortened the duration of cold symptoms in adults mean difference 8722263 days 95 CI 8722369 to 8722158 but no significant effect was seen among children 18 years mean difference 026 days 95 CI 8722078 to 025

Heterogeneity was slightly reduced in the subgroups I282 for adults I284 for children

The researchers observed that a reduction in the duration of cold symptoms was greater with high doses 880575 mg versus 75 mg of ionic zinc for a mean difference of 8722275 days 95 CI 8722389 to 8722160 than with lower doses mean difference 8722084 days 95 CI 8722150 to 8722018 In addition there was a significant interaction effect P0005 and heterogeneity was reduced I278 for high dose I289 for low dose

Although there was lowquality evidence that participants receiving zinc were less likely than controls to be symptomatic at one week there was no difference between groups in symptom severity or presence of symptoms at three days Science and colleagues noted

In addition the researchers reported that the occurrence of any adverse event RR 124 95 CI 105 to 146 bad taste RR 165 95 CI 127 to 216 and nausea RR 164 95 CI 119 to 227 were more common in the zinc group than in the placebo group

Adverse effects were common and should be the point of future study because a good safety and tolerance profile is essential when treating this generally mild illness the authors wrote

They noted that heterogeneity remained high in all subgroup analyses including by age dose of ionized zinc and zinc formulation This was cited as a primary limitation by the researchers since it remained unexplained despite exploration of several subgroups a priori and the quality of reported summary data

Until further evidence becomes available there is only a weak rationale for physicians to recommend zinc for the treatment of the common cold the researchers concluded The questionable benefits must be balanced against the potential adverse effects

Additional limitations included the fact that all studies analyzed were industryfunded and conducted in developed countries and that assumptions were made to calculate means and standard deviations of several trial estimates In addition ineffective blinding related to taste of the placebo may have contributed to bias in some of the trials the authors suggested

Date : 08 May, 2012
Reference : http://www.medpagetoday.com/InfectiousDisease/URItheFlu/32546

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