Zinc Acetate Lozenges To Treat the Common Cold

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The summary below is from the full report titled "Duration of Symptoms and Plasma Cytokine Levels in Patients with the Common Cold Treated with Zinc Acetate. A Randomized, Double-Blind, Placebo-Controlled Trial." It is in the 15 August 2000 issue of Annals of Internal Medicine (volume 133, pages 245-252). The authors are A.S. Prasad, J.T. Fitzgerald, B. Bao, F.W.J. Beck, and P.H. Chandrasekar.

What is the problem and what is known about it so far?

Ten careful studies of zinc lozenges for the treatment of common colds have been published. Five of these studies suggested that zinc shortens the duration of cold symptoms, but the other five suggested that it did not. Some researchers believe that the studies showing no benefit may have used incorrect formulations or doses that were too low. The process by which zinc might help colds has not been studied. Proinflammatory cytokines are substances that increase in the body with infection and may play a role in cold symptoms

Why did the researchers do this particular study?

To see whether zinc lozenges reduced the duration of cold symptoms and changed cytokine levels in persons with colds.

Who was studied?

Fifty adult students or employees of Wayne State University (Detroit, Michigan) who had had cold symptoms for less than 24 hours.

How was the study done?

The researchers randomly assigned each patient to take either one zinc acetate lozenge (containing 12.8 mg of zinc) or a placebo lozenge every 2 to 3 hours while awake as long as the cold symptoms lasted. Patients took no other cold remedies. Placebo lozenges looked and tasted like zinc lozenges but contained no active ingredient. Using a rating scale of none (0), mild (1), moderate (2), or severe (3), patients rated each of the following symptoms daily: sore throat, runny nose, nasal drainage, nasal congestion, cough, scratchy throat, hoarseness, muscle aches, fever, and headache. The researchers calculated daily symptom scores by adding up the symptom points each day (the lowest possible daily score was 0, and the highest possible score was 30). The end of the cold was the day on which a patient had no symptoms or only one mild symptom. Patients also recorded the occurrence of the following potential side effects: nausea, vomiting, abdominal pain, diarrhea, constipation, dry mouth, bad taste, and mouth irritation.

What did the researchers find?

Twenty-five patients assigned to take zinc and 23 assigned to take placebo completed the study. Cold symptoms lasted about 4.5 days in patients taking zinc and about 8 days in patients taking placebo. The duration of cough differed most: It lasted about 3 days in patients taking zinc and 6 days in patients taking placebo. Total symptom scores were lower in the zinc group than in the placebo group. Cytokine levels decreased more in patients taking zinc than in those taking placebo; however, statistical tests indicated that the difference could have been due to chance. Patients taking zinc reported more dry mouth and constipation than did patients taking placebo.

What were the limitations of the study?

The study was funded by a foundation related to the company that holds the patent for this type of zinc lozenges. Although the observed changes in cytokine levels are interesting, the study does not explain why therapy with zinc might improve cold symptoms.

What are the implications of the study?

Zinc acetate lozenges appear to reduce the duration of cold symptoms, especially cough, in adults who use the lozenges within 24 hours of developing such symptoms.