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Zinc Gluconate Lozenges for Treating the Common Cold: A Randomized, Double-Blind, Placebo-Controlled Study

Sherif B. Mossad, MD; Michael L. Macknin, MD; Sharon V. Mendendorp, MPH; and Pamela Mason, BSN, MBA
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From the Cleveland Clinic Foundation, Cleveland, Ohio. Acknowledgments: The authors thank Becton Dickinson (Rutherford, New Jersey) for supplying the digital thermometers, the Quigley Corp. (Doylestown, Pennsylvania) for supplying the active and placebo medication, McNeil (Fort Washington, Pennsylvania) for supplying acetaminophen, and Classics Restaurant (Cleveland, Ohio) for donating a dinner for two for a raffle to encourage patients to enroll in the study. The authors also thank John C. Godfrey, PhD, and Nancy J. Godfrey, PhD, for their help in designing this study and reviewing the manuscript, Tom Lang for medical editing, and Charlene Mahovlic for typing the manuscript. Grant Support: By the General Pediatrics Research Fund and the Departments of Infectious Diseases and General Pediatrics of the Cleveland Clinic Foundation. Requests for Reprints: Michael L. Macknin, MD, Department of Pediatrics and Adolescent Medicine, A 120, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195. Current Author Addresses: Drs. Mossad and Macknin, Ms. Medendorp, and Ms. Mason: The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195.

Copyright ©2004 by the American College of Physicians

Ann Intern Med. 1996;125(2):81-88. doi:10.7326/0003-4819-125-2-199607150-00001
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Background: The common cold is one of the most frequent human illnesses and is responsible for substantial morbidity and economic loss. No consistently effective therapy for the common cold has been well documented, but evidence suggests that several possible mechanisms may make zinc an effective treatment.

Objective: To test the efficacy of zinc gluconate lozenges in reducing the duration of symptoms caused by the common cold.

Design: Randomized, double-blind, placebo-controlled study.

Setting: Outpatient department of a large tertiary care center.

Patients: 100 employees of the Cleveland Clinic who developed symptoms of the common cold within 24 hours before enrollment.

Intervention: Patients in the zinc group (n = 50) received lozenges (one lozenge every 2 hours while awake) containing 13.3 mg of zinc from zinc gluconate as long as they had cold symptoms. Patients in the placebo group (n = 50) received similarly administered lozenges that contained 5% calcium lactate pentahydrate instead of zinc gluconate.

Main Outcome Measures: Subjective daily symptom scores for cough, headache, hoarseness, muscle ache, nasal drainage, nasal congestion, scratchy throat, sore throat, sneezing, and fever (assessed by oral temperature).

Results: The time to complete resolution of symptoms was significantly shorter in the zinc group than in the placebo group (median, 4.4 days compared with 7.6 days; P < 0.001). The zinc group had significantly fewer days with coughing (median, 2.0 days compared with 4.5 days; P = 0.04), headache (2.0 days and 3.0 days; P = 0.02), hoarseness (2.0 days and 3.0 days; P = 0.02), nasal congestion (4.0 days and 6.0 days; P = 0.002), nasal drainage (4.0 days and 7.0 days; P < 0.001), and sore throat (1.0 day and 3.0 days; P < 0.001). The groups did not differ significantly in the resolution of fever, muscle ache, scratchy throat, or sneezing. More patients in the zinc group than in the placebo group had side effects (90% compared with 62%; P < 0.001), nausea (20% compared with 4%; P = 0.02), and bad-taste reactions (80% compared with 30%; P < 0.001).

Conclusion: Zinc gluconate in the form and dosage studied significantly reduced the duration of symptoms of the common cold. The mechanism of action of this substance in treating the common cold remains unknown. Individual patients must decide whether the possible beneficial effects of zinc gluconate on cold symptoms outweigh the possible adverse effects.


common cold ; zinc


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Figure 1. Solid line equals zinc group; dotted line equals placebo group.
Kaplan-Meier curve for the duration of colds in 99 volunteers.
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Figure 2. Nasal symptoms were nasal drainage and nasal congestion. Solid line equals zinc group; dotted line equals placebo group.
Percentage of the original nasal symptoms score each day by treatment group.
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Figure 3. Throat symptoms were hoarseness, sore throat, and scratchy throat. Solid line equals zinc group; dotted line equals placebo group.
Percentage of original throat symptoms score each day by treatment group.
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