Swiss Echinacea Extract Shown Safe and Effective in Preventing Colds in Largest Echinacea Clinical Trial
by Amy C. Keller
2012; American Botanical Council
Jawad M, Schoop R, Suter A, Klein P, Eccles R. Safety and efficacy profile of Echinacea purpurea to prevent common
cold episodes: a randomized, double blind, placebo-controlled trial. Evid Based Complement Alternat Med.
2012:841315. Epub 2012 Sep 16.
and flu, associated with a variety of viral infections, are characterized by
symptoms such as sore throat, cough, and nose irritations, as well as systemic
complaints such as headache, malaise, and fever. The common cold alone causes
great discomfort and is a major reason for school and work absences, as well as
physicians visits.1 Preventative strategies have included antiviral
agents or vaccines targeted towards infection prevention or inhibition of viral
replication; however, common problems arise with adverse side effects (ASE)
and/or the failure to protect certain populations.
(Echinacea purpurea, Asteraceae) is
used widely as an immune system modulator as well as in common cold prevention
strategies.2 Many clinical studies investigating the use of
echinacea in cold prevention have shown conflicting results or have had too
small a sample size to detect significant effects. However, significant
preventive effects were observed when 3 trials on standardized echinacea
extracts were combined in a meta-analysis.3 (These studies were
conducted by Bioforce AG in cooperation with Sebastian Johnston, MD,
PhD, from the Imperial College in
London.) Finally, tolerability and safety are critical considerations for
therapies designed for long-term, preventive use. The most recent randomized,
double-blind, placebo-controlled trial investigated the safety profile and
efficacy of the long-term usage of a proprietary echinacea formulation for
prevention of colds and flu.
study took place at the Common Cold Center at Cardiff University in Cardiff, Wales. Healthy subjects were randomized to either echinacea or placebo for 4
months. At the initial clinical visit, subjects received study medication for 1
month in addition to a diary for documenting ASEs, incidences of colds and associated symptoms, and medication use other than given treatments. Subjects
brought unused treatments and completed diaries to monthly clinical visits and
also were given kits to take nasal swabs for viral identification.
alcoholic extract of fresh echinacea extract was used in this trial
(Echinaforce®, made from E.
purpurea, 95% aerial parts and 5%
roots, prepared by Bioforce AG; Roggwil, Switzerland). Material was
standardized to 5 mg/100 g of dodecatetraenoic acid isobutylamide and tested
negative for endotoxin. Placebo was comparable in appearance, smell, and taste,
with the same percentage of alcohol and identical packaging. Total dosage was
based on Bioforce AG’s instructions and consisted of 0.9 ml of extract or
placebo 3 times per day in water; this material was held in the mouth for 10
seconds (2,400 mg of extract daily) in order to achieve maximal local antiviral
and anti-inflammatory effects at the pharynx. If subjects had a cold, they were
asked to increase dosage to 0.9 ml 5 times per day (4,000 mg of extract).
Leftover bottles were weighed for remnant of extract, and diaries were consulted
to assess compliance.
were recruited on campus, at least 18 years old, and in good health with a
recent history of 2 or more colds per year. Those pregnant, who had a chance of
becoming pregnant, who were breastfeeding, who had a cold at the time of
recruitment, who were on either antiviral or antibacterial medication, who
abused drugs or alcohol, or who suffered from psychological diseases or
epilepsy were excluded. Exclusion criteria also did not permit subjects with
the following: a history of suicide attempts, upcoming surgery, chronic or
autoimmune diseases, and asthma or allergies, particularly to members of the
Asteraceae plant family. A preliminary study showed blinding to be efficient as
approximately half the subjects in both the echinacea and placebo groups
guessed that they had the echinacea treatment. Additionally, a power
calculation based on a beneficial effect of 25% with the echinacea treatment
and a protocol deviation and drop-out rate of 20% yielded an ideal sample size
of 750 participants for the efficacy variable (number of days with colds).
samples were taken from subjects for screening of blood cell counts and
hematological and other measurements. Both subjects and physicians were asked
to rate echinacea tolerability. Descriptions for ASEs as related to the
treatments ranged from “not related” to “certain.” Those ASEs that were
“possibly” associated with treatment were considered adverse drug reactions
(ADRs). Parameters for colds included the amount of colds, the total number of
days with colds, and colds that required addition medication. Characterization
of viral infections was also conducted.
of 755 subjects included and randomized, 82 subjects dropped out, leaving 673
who finished the study regularly. Reasons for subject dropout included loss of
contact (there was no contact post randomization; n=38), withdrawal of consent
(n=16), “technical reasons” (n=3), health or ASE problems (n=3), and unknown
reasons (n=22). There were no baseline differences between groups with the
exception of cold susceptibility; subjects randomized to the echinacea group
were, by chance, significantly more susceptible to colds than those in the
placebo group (P<0.05). This was expected to bias the efficacy results
against the echinacea group.
were reported by 9.0% of the echinacea group and 10.0% of the placebo group;
the echinacea treatment was identified to be non-inferior to placebo treatment
in regard to the rate of occurrence, as even fewer ADRs were observed. In the
echinacea group, 177 subjects documented 293 ASEs, and 172 subjects in the
placebo group mentioned 306 ASEs. Also, in the echinacea group, 4 ASEs resulted
in discontinuation of treatment, while 3 ASEs caused discontinuation in the
placebo group. One severe ASE was reported in the placebo group while none were
reported from the echinacea group. No significant differences were detected in
the amount of ASEs between groups. Also, no significant differences were
reported in the blood parameters either after echinacea treatment or between
groups. Assessment of tolerability by subjects resulted in ratings of “good” or
“very good” in 64% of the echinacea group and 71% of the placebo group.
in the echinacea group experienced 149 colds lasting a combined total of 672
days, while subjects in the placebo group reported 188 colds with a length of
850 days. The total number of days with colds was significantly fewer in the
echinacea group than the placebo group (P<0.05, as measured in the
intention-to-treat population). Those in the echinacea group also experienced
fewer recurring colds than those in the placebo group (65 vs. 100,
respectively; P<0.05). In addition, a greater number of subjects with colds
in the placebo group used medication such as aspirin, paracetamol (acetaminophen),
and ibuprofen as compared with those in the echinacea group (88 vs. 58,
the nasal swabs collected (n=201), viral infection was identified in 54 samples
from the echinacea group and 74 in the placebo group. Significantly fewer
samples from the echinacea group contained influenza, corona-, metapneumo-,
respiratory syncytial-, and parainfluenza viruses as compared the placebo group
(24 vs. 47, respectively; P<0.05). Additionally, in subjects with 100%
protocol compliance, 36 colds with a combined total duration of 155 days were
reported from the echinacea group (n=88) as compared with 58 colds in 268 days
in the placebo group (n=99, P<0.0001).
summary, preventive therapies for colds and flu should be both well tolerated and efficacious. The echinacea preparation used here exhibited a very “good”
safety profile for long-term usage. This study reports that echinacea long-term prevention was associated with fewer cold episodes, fewer days with colds, and
fewer colds that required additional medication, suggesting efficacy against
infection. The study mentions that these data may have been confounded by the
significant difference of cold susceptibly between groups and less use of
pain-relieving pharmaceutical drugs in the echinacea group. If an adjustment
for these co-variables had been conducted, an even more beneficial preventive
effect for the echinacea formulation probably would have been shown.
study also characterized viruses. Although the sample size was small, those in
the echinacea group had significantly fewer viral infections than those in the
placebo group. This may preliminarily indicate clinical antiviral activity as
it agrees with the authors’ in vitro
results on the same proprietary extract (Echinaforce). In conclusion, this
study claims to be not only the largest ever conducted on the clinical effects
of echinacea, but the first to employ the detection of specific viruses in this
manner. The conclusions from this well-powered, robust clinical trial contribute
substantially to the case for the use of echinacea preparations, particularly
this specific formulation, in common cold prevention.
—Amy C. Keller, PhD
1. National Institute of Allergy and Infectious Diseases:
common cold overview. August 17, 2012. Available at www.niaid.nih.gov/topics/commonCold/Pages/overview.aspx.
Accessed September 9, 2012.
2. Blumenthal M, Goldberg A, Brinckmann J, eds. Herbal Medicine: Expanded Commission E
Monographs. Austin, TX: American Botanical Council; Newton, MA: Integrative
Medicine Communications; 2000.
3. Schoop R, Klein P, Suter A, Johnston SL. Echinacea in the
prevention of induced rhinovirus colds: a meta-analysis. Clin Ther. February 2006;28(2):174-183.