Issue: 64 Page: 28-29
Echinacea purpurea Liquid Extract Effectively Treats the Common Cold in Adults
by Donald J. Brown
HerbalGram. 2004; 64:28-29 American Botanical Council
Echinacea purpurea Liquid Extract Effectively Treats the Common Cold in Adults
Reviewed : Goel V, Lovlin R, Barton R, et al. Efficacy of a standardized
echinacea preparation (Echinilin™) for the treatment of the common cold:
a randomized, double-blind, placebo-controlled trial. J Clin Pharm Ther. 2004;29:75–83.
Summary: In a
randomized, double-blind, placebo-controlled trial, 282 males and females aged
18-65 years with a history of two or more colds in the previous year, but
otherwise in good health, were recruited to study the efficacy of a
standardized Echinacea purpurea liquid extract (40% alcohol) in
treating the common cold. Manufactured by Natural Factors, Burnaby, British
Columbia, Canada, the extract Echinilin (sold in the U.S. as Echinamide™) is made from flowering tops of freshly
harvested plants and is standardized to contain alkamides/cichoric
acid/polysaccharides at concentrations of 0.25/2.5/25.5 mg/ml, respectively.
Subjects were randomized to receive either echinacea extract or placebo for 7
days and were instructed to begin treatment at the onset of the first symptom
related to a common cold. Treatment consisted of 10 doses the first day and 4
doses per day for the next 6 days. A dose was 4 ml of the echinacea extract or
placebo diluted in a half glass of water.
Participants were asked to complete a daily log documenting
the severity of their symptoms. Self-assessment was made on a 10-point scale: 0
= no symptom, 1–3 = a mild symptom, 4–6 = a moderate symptom, and 7–9 = a
severe symptom. The following cold symptoms were assessed daily: sore throat,
runny nose, sneezing, stuffy nose, watery eyes, chills, malaise, fever,
headache, sore muscles, hoarseness, shortness of breath, and cough. Total Daily
Symptom Scores (TDSS) were calculated by summing the daily scores of all
symptoms. The primary efficacy end point was the change in TDSS over the 7-day
treatment period. The secondary efficacy parameters were the change in total
symptom scores (overall mean) of specific symptoms, duration of symptoms
(number of days for which the total score was > 3), and response rate to the
treatments. Response rate was calculated as the percentage of subjects
demonstrating at least a 50% reduction in their maximum TDSS. In addition to
self-assessments, participants were also required to see a nurse on days 3 and
8.
Of the 282 subjects entered in the trial, 128 contracted a
common cold (59 received echinacea and 69 placebo) and were included in the
intent-to-treat (ITT) population. Participants who followed all elements of the
trial (“PP” group) were also separately analyzed. Throughout treatment, the
TDSS were significantly lower in patients taking echinacea compared to those
taking placebo (p < 0.05). The TDSS scores were found to be 23.1% lower in
the echinacea group than in the placebo group for those participants who
followed all elements of the trial (p < 0.01). All symptoms, with the
exception of cough, had significantly lower scores in the echinacea group
compared to the placebo group (p <0.05). In the PP group, 50% of subjects in
the echinacea group showed at least a 50% reduction of their maximum TDSS by day
4. This reduction in TDSS was not evident in the placebo group until day 5.5.
By day 7, the response rate increased to 95% in the echinacea group, but only
to 63% in the placebo group. These results were similar but less pronounced in
the ITT group. Gastrointestinal side effects (nausea, heartburn) were reported
by 13% of those taking echinacea compared to 9% taking placebo. Other mild side
effects such as itching, burning sensation and numbness of the tongue were
reported by 13% of the echinacea group and 11% of the placebo group,
respectively. However, no subjects withdrew due to these side effects.
Comments/Opinions:
Completed at the University of Alberta in Edmonton, Canada, this is the first
North American clinical trial to report efficacy for echinacea in the acute
treatment of the common cold. In addition to early intervention, another
possible key to this trial is the use of a higher dose on day one (40 ml) than
on the remaining days. In contrast to a negative U.S. pediatric trial published
last year (reviewed in this column in HerbalGram 62),1
this trial uses a dosing schedule similar to a positive European trial that
also used a liquid preparation made from the fresh-pressed aerial parts of E.
purpurea (Echinaguard®, another
trademark for Echinacin®, Madaus AG, Cologne, Germany).2
In that trial, subjects were treated with 20 drops of the liquid every 2 hours
during the first day of their symptoms and then 20 drops 3 times per day for
the remaining 9 days of the trial. Interestingly, a second, negative U.S.
echinacea trial did use a higher dose on day 1 of the trial,3 but
comparison is difficult due to variations in the different preparations used in
the trials. The product in the negative U.S. trial was an encapsulated dried
powder made from the aerial parts and roots of E. purpurea and roots of E. angustifolia. Three other trials, Goel et al,4 Taylor
et al, and Hoheisel et al, used an alcohol-based, liquid preparation made from
the fresh juice. The preparation in the Taylor et al trial was a syrup prepared
from the dried fresh-pressed
juice of E. purpurea aerial
parts. (The presence of the alcohol at about 22% is for preservation only; the
alcohol is not used as a solvent
as is the case with many commonly available echinacea extracts.) It may be beneficial to compare different dosing
regimens as well as higher doses in future echinacea trials.
Because the preparation administered to subjects was a
liquid, this study may not have been truly double blind. This criticism was
pointed out by HerbalGram reviewer Bruce
Barrett, PhD, professor at the University of Wisconsin Medical School and
author of several critical reviews and clinical trials on echinacea.
Unfortunately, this problem is inherent in any study using liquid preparations
because it may be possible for blind participants to distinguish the identity
of the true, active preparation from the placebo. If subjects in this trial
were able to correctly identify echinacea as the active ingredient being
administered, they may have over-reported positive outcomes. However, the trial
authors point out that “The placebo was made to look, taste, and smell like
echinacea extract but contained no detectable alkamides, cichoric acid, or
polysaccharides.” They further note that “Blinding was also maintained adequately
during the treatment period. On completion of the study, approximately 50% of
the subjects in both groups could not guess correctly whether they had received
echinacea or placebo.” Thus, insofar as this trial is concerned,
double-blinding of participants using liquid preparations appears to have been
successfully accomplished.
In his review, Dr. Barrett also noted that the magnitude of
the apparent treatment effect may be overstated in this trial. The use of the
term “response rate” is inappropriate for describing responses to the common
cold, an ailment for which everyone recovers eventually. The primary outcomes
instrument, while reasonable at face value, has not been tested for
reliability, responsiveness, and validity. Therefore, the choice of cutoff for
response rate is retrospective, and may overstate a modest effect size, i.e.,
the significance of the improvement in the echinacea group may not be quite as
great as suggested by the results of the study.
The preparation in this trial is unique in its
standardization of three groups of constituents considered to be active in both
the aerial and root parts of echinacea. The investigators point to oral
dose-response studies in rats showing enhanced alveolar macrophage function
after 4 days of treatment.1 As
respiratory macrophage activity is thought to be an important first defense
against viral respiratory infection, they speculate that this may explain the
efficacy of the product in this trial. It would be constructive if the
manufacturers of this product were to produce human data in a future trial to
support these speculations.
Practice Implications:
The results of this trial place echinacea back on the list of considerations
for treating the common cold in adults. It is important to note that the trial
used a dose on the first day of treatment that was 2.5 times higher than the
dose used on the following 6 days of treatment. In contrast to the negative
pediatric trial published in the Journal of the American Medical
Association,1 there
were no reports of skin rash in this trial.
Note: This online version contains a clarification edit to the original article related to the product name in the U.S.
References:
1. Taylor JA, Weber W, Standish L, et al. Efficacy and safety of echinacea
in treating upper respiratory tract infections in children. JAMA. 2003;290(21):2824–2830.
2. Hoheisel O, Sandberg M, Bertram S, et al. Echinagard™ treatment shortens
the course of the common cold: a double-blind, placebo-controlled clinical trial.
Eur J Clin Res. 1997;9:261–268.
3.Barrett B, Brown R, Locken K, et al. Treatment of the common cold with unrefined
echinacea: a randomized, double-blind, placebo-controlled trial. Ann Intern
Med. 2002;137(12):939–946.
4. Goel V, Chang C, Slama JV, et al. Echinacea stimulates macrophage function
in lung and spleen of normal rats. J Nutr Biochem. 2002;13:487–492.
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