PRACTICE CHANGER
Advise patients to start taking zinc supplements (available as tablets, syrup, or lozenges) within 24 hours of the onset of a cold.1
Singh M, Das RR. Zinc for the common cold. Cochrane Database Syst Rev. 2011;(2):CD001364.
STRENGTH OF RECOMMENDATION
A: Based on a meta-analysis of 13 randomized placebo-controlled trials.
ILLUSTRATIVE CASE
A healthy 31-year-old woman schedules a visit because of congestion and rhinorrhea. She tells you that her cold symptoms developed in the last day or 2 and asks for something to speed her recovery. What can you suggest?
Americans experience roughly 500 million episodes of noninfluenza-related viral respiratory tract infections annually (ie, common colds), or roughly 2.5 episodes per person each year. The total economic burden of the common cold is nearly $40 billion annually.2
Most cold remedies offer little relief
We’ve all cared for patients with cold symptoms. And despite the desire to help, many of us have been frustrated by the fact that there is no cure for the common cold, and most over-the-counter therapies offer little or no relief.
What about zinc? Zinc has been in and out of favor as a treatment for the common cold, based on contradictory findings, since the first randomized trial was published in 1984.3
A 1998 systematic review (which did not include a quantitative synthesis of data) suggested that zinc was beneficial in reducing the duration and severity of cold symptoms.4 A meta-analysis published in 2000 found that zinc was ineffective compared with placebo in reducing the likelihood that cold symptoms were present after 7 days.5 A meta-analysis published in June 2011 concluded that zinc lozenges reduce the duration of cold symptoms by 12% to 48%, but only at daily doses >75 mg.6
These conflicting results have made it difficult to recommend zinc to patients—until now.
STUDY SUMMARY: Zinc for colds? Cochrane review provides convincing evidence
The 2011 Cochrane review that’s the focus of this PURL1 addressed the question: Does zinc reduce the duration and severity of the common cold? The review also assessed zinc’s ability to prevent colds, although only 2 studies focused on prevention.
The researchers included only randomized, double-blind, placebo-controlled trials in which oral zinc supplementation was used for ≥5 consecutive days for treatment or ≥5 months for prevention. Studies included patients of any age, taking any dosage and any formulation of zinc.
Primary outcomes included the duration of symptoms, the severity of symptoms, and the incidence of the common cold in prevention studies. Secondary outcomes included the proportion of patients symptomatic after 3, 5, and 7 days of treatment, the time to resolution of individual symptoms (eg, cough), change in individual symptom scores, school absences, antibiotic use, and adverse effects.
Thirteen therapeutic trials and 2 prevention trials met the inclusion criteria. These studies, all of which were judged to be of high quality with a low risk of bias, had a total of 996 patients in the therapeutic trials and 394 patients in the prevention trials. Participants ranged in age from 1 to 65 years.
Therapeutic trials. In general, therapeutic studies included lozenges containing 10 to 24 mg zinc gluconate, with one lozenge taken every 1 to 4 hours during the day for 3 to 7 days. In one therapeutic trial that enrolled only children ages 1 to 10, the intervention group took zinc sulfate syrup (15 mg bid) for 10 days. In 11 of the 13 therapeutic studies, treatment began in the first 24 hours of symptoms; in the remaining 2, it began within 48 hours of symptoms.
Ten studies reported on duration of symptoms; 6 of them were similar enough to allow for pooling of results. The pooled results showed that patients who took zinc had a shorter duration of cold symptoms (0.97 days; 95% confidence interval [CI], -1.56 to -0.38), compared with those on placebo. Pooled results from 5 trials revealed that zinc significantly reduced the severity of symptoms by a standard effect size of 0.39 (95% CI, -0.77 to -0.02), which is considered a small to moderate effect.