Dosage Too Low in New Echinacea Trial, Says
Herbal Science Group
August 2, 2005
The nonprofit American Botanical Council (ABC), an Austin, Texas-based research
and education organization, has reviewed a new clinical trial on the popular
herb echinacea for use in a specific kind of induced virus, published Thursday
in the New England Journal of Medicine.1 The study concluded that the echinacea
preparations did not prevent or help treat symptoms of a specific virus applied
to the test subjects. ABC has found several aspects of the design of the study
worthy of clarification, and comments on the potential misinterpretations of the
significance of this study.
First, the extracts used were made in a university laboratory and do not
correlate with commercial echinacea products currently available to consumers.
Second, the dosages used in this trial were probably too low. The echinacea
preparations used in the study might have shown activity at more frequent dosing
intervals and/or higher dosage levels - as is often the case with contemporary
echinacea use.
The new trial utilized extracts made from the roots of a species of echinacea
called Echinacea angustifolia. The randomized, double-blind, placebo-controlled,
seven-arm trial was conducted on 437 college students who had a particular type
of rhinovirus inserted into their nostrils (the results were calculated on 399
subjects). In the trial, the echinacea preparations were tested to see if they
had a preventive effect or if they could help treat the symptoms caused by the
rhinovirus. The students who received the three different echinacea preparations
and were sequestered in a hotel room did not experience fewer infections, fewer
symptoms, or a reduction in the duration of symptoms, compared with those who
received the placebo.
The trial utilized three doses of 1.5 milliliters each of the three
laboratory-produced echinacea extracts, presumably equivalent to about 300
milligrams of the dried powdered root in each dose (equivalent to 900 mg per day
of the dried root). This level was chosen for the trial because it is the dose
recommended by the German government's expert herb panel called the Commission
E, which had conducted reviews of the research published on various types of
echinacea in the scientific and medical literature in the early 1990s.2
According to ABC various international monographs have acknowledged the
generally higher dose used for echinacea root products. The World Health
Organization (WHO) monograph for Echinacea root (“Radix Echniaceae”) has a
dosage for Echinacea angustifolia root at the equivalence of 3 gm per day of the
dried root.3 This same dosage is also acknowledged in the more recently
developed draft monographs on Echinacea from the Canadian Natural Health
Products Directorate.4
This dosage level is about 330% higher than the dosage of the echinacea
preparations given in the NEJM trial. This supports ABC's contention that the
preparations may have been under-dosed and that the trial might have shown a
potentially positive trend if a higher dosage and/or increased frequency of
administration had been followed.
“It would have been optimal if this trial had tested the echinacea
preparations at more frequent and/or higher doses,” said Mark Blumenthal,
Founder and Executive Director of ABC. “Dosage is one of the most important
aspects in assessing any therapeutic agent. Many clinicians who recommend
echinacea for treatment of upper respiratory tract infections related to colds
and flu normally utilize a frequency of use and/or a total daily dose that is
higher than the one used in this trial. This is also true for consumer
self-medication with many commercial echinacea preparations according to some
label dosage suggestions.”
American
Botanical Council
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