Indications
The purple coneflower Echinacea purpura, and its close
relatives, E. angustifolia and E. pallida, are the source of
the herb Echinacea, which is widely popular as a nonspecific
immune stimulant. These perennials are native
to the prairies of North America and are now widely
grown garden ornamentals.The root and aerial parts of
the plant are the portions used, and the preparation’s
potency can be verified by the transient tingling sensation
produced when it is tasted. Echinacea contains
alkamides, caffeic acid esters (echinacoside, cichoric
acid, caftaric acid), polysaccharides (heteroxylan), and
an essential oil. Some echinacea products are standardized
for their echinacoside content. In the past, adulteration
with American feverfew (Parthenium integrifolium)
was common. Echinacea is now sold either by
itself or in combination with golden seal or zinc for the
treatment of colds and influenza.
General Description
One estimate stated that, in Germany alone, there are 800 echinacea-containing drugs, including several homeopathic preparations. Three species are identified as echinacea: E. angustifolia, Echinacea pallida, and Echinacea purpurea. All are used for medicinal purposes, and they have similar properties. There are slight differences among the species with regard to the anatomical distribution of active constituents. There is no doubt that echinacea has immunomodulating properties. The chemistry of the constituents of the plant has been studied extensively, but it is difficult to correlate a major activity with any plant fraction.
Mechanism of action
Echinacea extracts appear to stimulate the number and
activity of immune cells (i.e., increasing physiological
levels of tumor necrosis factor and other cytokines)and
to increase leukocyte mobility and phagocytosis.The extracts
also have antiviral and antiinflammatory properties
and inhibit bacterial hyaluronidase.
Clinical Use
There are numerous studies on echinacea in the literature,
many of which indicate either an in vitro immune
stimulation or a significant clinical reduction in the
severity and duration of upper respiratory viral symptoms,
especially when taken early in the onset of symptoms.
Despite several of these meta-analyses concluding
that echinacea is an effective immunomodulator of
acute infection, there is still controversy as to the extent
of its clinical effectiveness. A number of trials now
clearly indicate that echinacea is unlikely to be effective
in the prevention of colds, even if it may slightly shorten
their course.
In vitro antiinflammatory effects have been documented,
and the herb has a long history of being used
externally for wound healing, psoriasis, and the reduction
of skin irritation. Although there are a few small
positive studies, the available e
Side effects
Echinacea appears to be a very safe herb, producing only
minor gastrointestinal (GI) side effects and an occasional
allergic reaction, usually in atopic patients already sensitized
to other members of the Compositae plant family.
Anaphylaxis has occurred rarely. Use in HIV is discouraged
because of the concern that long-term therapy may
eventually suppress the immune system.
It is recommended that echinacea not be taken by
anyone for more than 8 continuous weeks, and most
clinical use is under 2 weeks’ duration. Echinacea has
not yet been shown to be safe in pregnant or breastfeeding
women and small children. No specific
herb–drug interactions are reported, but for theoretical
reasons those taking immunosuppressant drugs should
avoid echinacea.
