Bruce Barrett, MD, PhD; Roger Brown, PhD; Dave Rakel, MD; Marlon Mundt, PhD; Kerry Bone, Dip Phyto; Shari Barlow, BA; Tola Ewers, MS
Echinacea is widely used to treat the common cold.
To assess the potential benefits of echinacea as a treatment of common cold.
Randomized, controlled trial. (ClinicalTrials.gov registration number: NCT00065715)
Dane County, Wisconsin.
719 patients, aged 12 to 80 years, with new-onset common cold.
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.
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.
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).
Higher-than-expected variability limited power to detect small benefits.
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.
National Center for Complementary and Alternative Medicine, National Institutes of Health.
Echinacea is a popular nonprescription treatment for the common cold. The efficacy of echinacea in this regard continues to be debated after hundreds of studies.
In this randomized, controlled trial, a minor, nonstatistically significant decrease in illness duration and severity was found in participants who received either blinded or open-label echinacea compared with those who received blinded placebo or no pills.
Higher-than-expected variability in the natural history of cold episodes may have limited the power of this study to demonstrate treatment differences.
This study is unlikely to change the debate on the efficacy of echinacea in treating the common cold.
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Barrett B, Brown R, Rakel D, Mundt M, Bone K, Barlow S, et al. Echinacea for Treating the Common Cold: A Randomized Trial. Ann Intern Med. ;153:769–777. doi: 10.7326/0003-4819-153-12-201012210-00003
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Published: Ann Intern Med. 2010;153(12):769-777.
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