Clinical Question: Does zinc nasal gel reduce the duration of the common cold?
Setting: Outpatient (any)
Study Design: Randomized, controlled trial (double-blinded)
Synopsis: Zinc lozenges have proved effective in six randomized trials and ineffective in eight other trials. Meta-analyses are equivocal. Advocates for zinc suggest that the delivery vehicle may be part of the problem; in this trial, researchers evaluated a zinc nasal gel.
Eighty patients were recruited from advertisements and were included in the trial if they were 18 to 55 years of age, had cold symptoms for 24 to 48 hours, and had either two major and at least one minor symptom, or one major and at least three minor symptoms. Major symptoms included nasal drainage and sore throat; minor symptoms included nasal congestion, sneezing, scratchy throat, hoarseness, cough, headache, muscle aches, and oral temperature above 37°C (98.6°F). These symptoms seem reasonable, although the definition of fever is too low. Patients with diabetes, those with a uncorrected deviated nasal septum or recurrent sinusitis, and patients who smoked were excluded from the trial.
Patients were randomized with concealed allocation to receive zincum gluconicum, 120 μL via metered-dose applicator, or placebo. Patients and investigators were blinded, and after one day patients could not guess whether they were in the active treatment or control group. The primary outcome was the time to resolution of all cold symptoms. Patients completed a diary of symptoms and adverse effects twice a day, rating each on a scale from zero (none) to 3 (severe). Many secondary outcomes were measured, but we will focus on the primary outcome.
The groups were similar at the start of the study, with 40 patients in each group. Two patients in the control group were lost to follow-up and, because there were no follow-up data, were excluded from the analysis. Three patients in the treatment group and one in the control group were diagnosed with an illness other than the common cold and discontinued treatment, but were still included appropriately in the analysis.
The time to resolution of all symptoms was shorter in the treatment group (4.3 versus 6.0 days for placebo; P = .002), and the time to resolution also was shorter for all individual symptoms, except headache, muscle aches, and fever. No statistically significant difference was noted between groups for each adverse effect. More patients in the treatment group had any adverse effect (31 percent versus 14 percent in the placebo group), although no test of statistical significance was reported for this comparison, which is questionable.
Bottom Line: Zinc nasal gel was effective in this small study, reducing the duration of cold symptoms by 1.7 days. It was well tolerated, although minor adverse effects were more common in the treatment group. (Level of Evidence: 1b)