Echinacea for Treating the Common Cold
A Randomized Trial
- Bruce Barrett, MD, PhD;
- Roger Brown, PhD;
- Dave Rakel, MD;
- Marlon Mundt, PhD;
- Kerry Bone, Dip Phyto;
- Shari Barlow, BA; and
- Tola Ewers, MS
Abstract
Background: Echinacea is widely used to treat the common cold.
Objective: To assess the potential benefits of echinacea as a treatment of common cold.
Design: Randomized, controlled trial. (ClinicalTrials.gov registration number: NCT00065715)
Setting: Dane County, Wisconsin.
Patients: 719 patients, aged 12 to 80 years, with new-onset common cold.
Intervention: Patients were assigned to 1 of 4 parallel groups: no pills, placebo pills (blinded), echinacea pills (blinded), or echinacea pills (unblinded, open-label). Echinacea groups received the equivalent of 10.2 g of dried echinacea root during the first 24 hours and 5.1 g during each of the next 4 days. Indistinguishable placebo tablets contained only inert ingredients.
Measurements: The primary outcome was the area under the curve for global severity, with severity assessed twice daily by self-report using the Wisconsin Upper Respiratory Symptom Survey, short version. Secondary outcomes included interleukin-8 levels and neutrophil counts from nasal wash, assessed at intake and 2 days later.
Results: Of the 719 patients enrolled, 713 completed the protocol. Mean age was 33.7 years, 64% were female, and 88% were white. Mean global severity was 236 and 258 for the blinded and unblinded echinacea groups, respectively; 264 for the blinded placebo group; and 286 for the no-pill group. A comparison of the 2 blinded groups showed a 28-point trend (95% CI, −69 to 13 points) toward benefit for echinacea (P = 0.089). Mean illness duration in the blinded and unblinded echinacea groups was 6.34 and 6.76 days, respectively, compared with 6.87 days in the blinded placebo group and 7.03 days in the no-pill group. A comparison of the blinded groups showed a nonsignificant 0.53-day (CI, −1.25 to 0.19 days) benefit (P = 0.075). Median change in interleukin-8 levels and neutrophil counts were also not statistically significant (30 ng/L and 1 cell/high-power field [hpf] in the no-pill group, 39 ng/L and 1 cell/hpf in the blinded placebo group, 58 ng/L and 2 cells/hpf in the blinded echinacea group, and 70 ng/L and 1 cell/hpf in the open-label echinacea group).
Limitation: Higher-than-expected variability limited power to detect small benefits.
Conclusion: Illness duration and severity were not statistically significant with echinacea compared with placebo. These results do not support the ability of this dose of the echinacea formulation to substantively change the course of the common cold.
Primary Funding Source: National Center for Complementary and Alternative Medicine, National Institutes of Health.
Article and Author Information
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Acknowledgment: The authors thank St. Marys Hospital for allowing the use of the Employee Health clinic room for physician visits and nasal wash collection; the UW Department of Family Medicine for providing an institutional base and collegial support; Mary Beth Plane, PhD, and Terry Little for assistance with editing and formatting; Rebecca Marnocha and the UW Hospital and Clinic's Pharmaceutical Research Center for putting pills in bottles and randomization codes in envelopes; and the many research participants who generously contributed with their time and energy during a period of illness.
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Grant Support: By the National Center for Complementary and Alternative Medicine at the National Institutes of Health (grant R01AT001428 and a Patient-Oriented Career Development Grant [K23 AT00051] to Dr. Barrett) and the Robert Wood Johnson Foundation Generalist Physician Faculty Scholars Program (Dr. Barrett). MediHerb (Queensland, Australia) provided the placebo and echinacea tablets used in this trial and conducted the phytochemical assays, all free of charge. When the National Institutes of Health funds ran out before data collection had been completed, Deans Robert Golden and Paul DeLuca of the UW School of Medicine and Public Health facilitated financial support to allow the project to reach enrollment goals.
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Potential Conflicts of Interest: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M10-0558.
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Reproducible Research Statement: Study protocol and data set: Available from Dr. Barrett (address below). Statistical code: Not available.
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Requests for Single Reprints: Bruce Barrett, MD, PhD, Department of Family Medicine, University of Wisconsin–Madison, 1100 Delaplaine Court, Madison, WI 53715.
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Current Author Addresses: Drs. Barrett and Mundt, Ms. Barlow, and Ms. Ewers: Department of Family Medicine, University of Wisconsin, 1100 Delaplaine Court, Madison, WI 53715.
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Dr. Brown: Department of Nursing, University of Wisconsin, Clinical Science Center-H6, Box 2455, 600 Highland Avenue, Madison, WI 53792.
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Dr. Rakel: University of Wisconsin Integrative Medicine, 595 Science Drive, Madison, WI 53711.
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Ms. Bone: Research & Development, MediHerb, Box 713, Warwick, Queensland 4370, Australia.
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Author Contributions: Conception and design: B. Barrett, R. Brown, D. Rakel, M. Mundt, K. Bone.
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Analysis and interpretation of the data: B. Barrett, R. Brown, D. Rakel, M. Mundt, T. Ewers.
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Drafting of the article: B. Barrett, R. Brown, D. Rakel, M. Mundt.
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Critical revision of the article for important intellectual content: B. Barrett, D. Rakel, M. Mundt, K. Bone.
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Final approval of the article: B. Barrett, R. Brown, D. Rakel, M. Mundt, K. Bone, T. Ewers.
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Provision of study materials or patients: K. Bone, S. Barlow.
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Statistical expertise: R. Brown, M. Mundt, T. Ewers.
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Administrative, technical, or logistic support: S. Barlow.
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Collection and assembly of data: S. Barlow.
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