Zinc Lozenges Study Proves Effectiveness

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Are zinc acetate lozenges effective in decreasing the duration of symptoms of

the common cold?

Source: Journal of Family Practice, Dec, 2000, by A.

* BACKGROUND Of the 10 published randomized controlled trials, only 5

reported that zinc lozenges reduced the duration of cold symptoms. The

reasons for the different results among these trials include differences in

doses, salts, and formulations of zinc lozenges; differences in study design;

and difficulty in truly blinding study participants.

* POPULATION STUDIED Fifty ambulatory volunteers older than 18 years

were recruited within 24 hours of developing cold symptoms. Potential

participants were students, staff, or employees of Wayne State University who

had at least 2 of 10 cold symptoms: cough, headache, hoarseness, muscle

ache, nasal drainage, nasal congestion, scratchy throat, sore throat,

sneezing, and fever. Exclusion criteria included pregnancy,

immunodeficiency disorder, any chronic illness, and previous use of zinc

lozenges. The treatment groups did not differ significantly in terms of age (37

[+ or -] 11 years), however, more patients receiving placebo were smokers

(35% vs 20%) and had an allergy history (15% vs 8%).

* STUDY DESIGN AND VALIDITY The study was a prospective randomized

double-blind trial. The participants used 1 lozenge containing either 12.8 mg

of zinc (as the acetate) or placebo every 2 to 3 hours while awake for as long

as they had cold symptoms. No other cold preparations were allowed.

Peppermint oil was used to mask the taste of zinc. Subjective cold symptom

scores and the number of lozenges used were recorded daily by the

participants. Plasma zinc and proinflammatory cytokine levels were measured

on day 1 and after patients were well. Side effects were assessed by

completion of a questionnaire at the end of the trial rather than being

recorded daily.

The appropriate study design was used for this efficacy trial. Two patients in

the placebo group dropped out on day 2; all other patients completed the

study and were included in the analysis. The patients, the research consultant

preparing the randomization code and packages of medications, and a

research assistant distributing the study medication were not aware of

treatment assignment (ie, allocation was concealed).

* OUTCOMES MEASURED Both patient-oriented (cold symptoms) and

disease-oriented (plasma levels of zinc and cytokines) outcomes were used

to assess the patients. The primary outcome was average duration of cold

symptoms.

* RESULTS Zinc-treated patients had lower overall severity scores (P [is less

than] .002, test for treatment x time interaction), as well as a significantly

shorter mean duration of all cold symptoms, 4.5 versus 8.1 days (3.6-day

difference; 95% confidence interval, 2.6-4.6 days; P [is less than] .01). By day

4, the average severity score in the zinc group was half that in the placebo

group (2.7 vs 5.4 out of a possible 30). Of the 10 measured cold symptoms,

only the duration of nasal discharge and cough were significantly shorter in

the zinc-treated patients.

The average number of lozenges taken per day did not differ between

treatment groups (6.2 for zinc and 5.8 for placebo). Patients in the zinc group

had a statistically significant higher incidence of dry mouth (P=.003) and

constipation (P=.02). Although it did not reach statistical significance, zinc-

treated patients experienced more bad taste (52% vs 26%, P=.08).

RECOMMENDATIONS FOR CLINICAL PRACTICE

The zinc acetate lozenge formulation used in this well-designed study was

more effective than placebo in decreasing the duration and severity of cold

symptoms, especially cough and nasal discharge. However, twice as many

zinc-treated subjects correctly identified their lozenges at the end of the

study,

suggesting that blinding may not have been completely maintained. Also, the

2 groups differed with regard to potential confounders (ie, smoking status and

allergy history). Despite these shortcomings, this study adds to the growing

evidence that certain zinc lozenge formulations shorten the duration and

decrease the severity of cold symptoms.