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Treat your cold with zinc

Robin Wulffson MD's picture
common cold, rhinovirus, zinc, treatment

A multitude of remedies are available for the treatment of the common cold, which is caused by a rhinovirus infection. The infection causes suffering among adults two to four times a year and infects children eight to ten times a year. One proposed remedy is formulations that contain zinc, which inhibits replication of the virus. Canadian researchers conducted a meta-analysis to evaluate both the effectiveness and safety of zinc for the treatment of a rhinovirus infection. (A meta-analysis is the review of data from a number of similar studies to clarify results.) The investigators published their findings online on May 7 in the Canadian Medical Association Journal.

The researchers searched electronic databases and other sources for studies involving zinc for patients of any age published through to September 30, 2011. They included all randomized controlled trials comparing orally administered zinc with s placebo or no treatment. The assessments for study inclusion, data extraction, and risk-of-bias analyses were conducted in duplicate.

The meta-analysis was comprised of 17 clinical trials involving a total of 2121 individuals ranging from 1 to 65 years of age. Three trials included children less than 18 years old, 13 included adults, and one trial included both adults and children. Colds were either naturally acquired (13 trials) or experimentally induced (4). All treatment regimens were compared to a placebo. They 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). The length of treatment was different in all trials (range: 3 to 14 days or until symptom resolution).

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The investigators found that, compared with subjects given a placebo, those receiving zinc had a shorter duration of cold symptoms (average difference: 1.65 days); however, heterogeneity was high. (Heterogeneity refers to variability or differences between studies in the estimates of effects.) Interestingly, zinc shortened the duration of cold symptoms in adults; however, no significant effect was found among children. Heterogeneity remained high in all subgroup analyses, including by age, dose of ionized zinc, and zinc formulation. The occurrence of any adverse event, ranging from bad taste to nausea, was more common in the zinc group than in the placebo group.

The authors concluded that the results of the meta-analysis revealed that oral zinc formulations may shorten the duration of symptoms of the common cold. They cautioned, however, that large high-quality trials were indicated before definitive recommendations for clinical practice could be made. They noted that adverse effects were common; thus, they recommended that these events should be the focus of a future study because “a good safety and tolerance profile is essential when treating this generally mild illness.”

The viral infection is referred to as the “common cold” because more than 1 billion cases of colds occur in the United States each year. Children usually catch colds from other children; parents often get catch colds from contact with children. Colds are the most common reason that children miss school and parents miss work. Colds can occur year-round, but they occur mostly in the winter (even in areas with mild winters). In areas where there is no winter, colds are most common during the rainy season. When someone has a cold, their runny nose is teeming with cold viruses. Sneezing, nose-blowing, and nose-wiping spread the virus. One can catch a cold by inhaling the virus if one is sitting close to someone who sneezes, or by touching one’s nose, eyes, or mouth after touching something contaminated by the virus. Using a shared telephone in an office setting is common method for acquiring a cold. Wiping the mouthpiece with a sanitary wipe can prevent an infection.

Reference: Canadian Medical Association Journal