Echinacea for Colds
Echinacea for Colds
November 2000; Volume 3; 128-130
By V. Jane Kattapong, MD, MPH
"The most high hath created medicines out of the earth, and a wise man will not abhor them."
Ecclesiasticus 38:4
As winter is nearly here, many of us anticipate patients’ questions regarding the usefulness of echinacea as a treatment for the common cold.
Since 1994, when Congress enacted the Dietary Supplement Health and Education Act, echinacea has become one of the most popular herbal remedies in the United States. Since this topic was first addressed in these pages by Udani and Ofman,1 only a small amount of new evidence has become available. However, these data may provide us with additional advice to offer patients who ask about the usefulness of echinacea.
Traditional Uses
A member of the daisy family (Asteraceae), echinacea also is known as the purple coneflower. There are nine different species of echinacea in the United States and southern Canada. American Indians have used echinacea preparations as antiseptics and analgesics for hundreds of years. Echinacea has been used as a treatment for colds, tonsillitis, toothaches, intestinal pain, snake bites, rabies, seizures, wound infection, sepsis, and cancer.2-4
One hundred years ago, echinacea was the best-selling native medicinal plant in the United States;3 however, its use in the United States declined greatly after the development and distribution of antibiotics. In the last six years echinacea has become wildly popular; in 1998, retail sales of echinacea preparations in the United States totaled nearly $70 million.5
Modern Uses
Echinacea has enjoyed even greater popularity in Europe, especially in Germany.6 More than 500 different echinacea-containing products were available in Germany in 1996.7 Modern-day European uses for echinacea are similar to traditional Native American uses; proposed indications for echinacea have included colds, upper and lower respiratory tract infections, chronic arthritis, cancer, yeast infections, bacterial infections, chronic fatigue syndrome, skin diseases, wounds, ulcers, and chronic pelvic infections.
Mechanism of Action
Echinacea is believed to act either via immunomodulatory enhancing properties or via direct inhibition of virus replication.8 The plant is composed of seven active constituents, including polysaccharides, flavonoids, essential oils, polyacetylenes, alkylamides, caffeic acid derivatives (such as echinacoside), and miscellaneous chemicals.1 Immunologically active components are believed to be polysaccharides, glycoproteins, caffeic acid derivatives, and alkamides.9
Clinical Trials
A literature search revealed four well-designed, controlled studies in the medical literature evaluating echinacea as a treatment for the common cold.
In the first study, adult volunteers from the Medical University of South Carolina community were recruited to receive exposure to rhinovirus type 23.8 After the initial virus challenge, the 117 subjects received either an echinacea preparation or placebo for five days. The echinacea preparation was standardized to contain 0.16% cichoric acid and minimal amounts of echinacosides and alkamides. No significant differences were seen between the treatment and control groups in incidence of rhinovirus infection, clinical colds, symptoms, or severity of symptoms. No side effects of echinacea were reported in this study.
In a similar study, Melchart treated 302 volunteers with either an E. purpurea extract or placebo for 12 weeks.10 No significant difference was found between incidence of common colds or symptom severity between the two groups.
In the third study, Grimm randomly assigned 108 patients with a history of more than three colds or respiratory symptoms in the preceding year to receive either E. purpurea extract or placebo.7 Subjects received 4 ml echinacea or placebo bid for eight weeks. However, it is unclear if the concentrations of active ingredients were equivalent in each of the aliquots.
There were no significant differences between the two groups in number of colds or respiratory infections, median duration of colds or respiratory infections, or severity of infections. There was no significant difference between the two groups in incidence of side effects. In the treatment group, reasons for study withdrawal included nausea (n = 1), constipation (n = 1), bad taste of medication (n = 1), and unspecified (n = 1). In the placebo group, reasons for withdrawal included sweating and paresthesia (n = 1), bad taste of medication (n = 1), and unspecified (n = 1).
In the fourth study, Henneicke-von Zepelin enrolled 263 patients presenting to one of 15 study sites.11 Patients with an acute common cold were randomized to receive placebo or a combination herbal remedy containing echinacea and other herbal ingredients. A composite score was created to incorporate intensity of cold symptoms, general well being, and severity of illness. An analysis of efficacy parameters demonstrated significantly greater efficacy for the herbal remedy. It is impossible to determine whether any of the effectiveness was derived from the echinacea or one of the other herbal ingredients. In addition, the validity of the efficacy score was not established.
Other Literature
The bulk of the limited research on echinacea is in German; very little research on echinacea has been undertaken in the United States. Although few well-designed, controlled studies demonstrate echinacea’s efficacy as a common cold treatment, other weaker clinical evidence from Germany suggests that echinacea may decrease severity and duration of colds and upper respiratory infections if started at the time symptoms begin and continued for 7-10 days.12 Reviews of existing clinical studies found that the bulk of the literature contained methodological flaws, but suggest that echinacea may have efficacy for treating, but not preventing, colds and upper respiratory infections.13,14
Echinacea Preparations
A systematic review of the literature regarding
echinacea’s effectiveness as a cold remedy meets with a serious obstacle: lack of product standardization. Preparations vary according to plant species and plant components, as well as variability between different plants in concentrations of active components.
E. angustifolia, E. pallida, and E. purpurea are the three echinacea species used medicinally. Both the processing and application methods introduce sources of variability. A product may be prepared from one or several plant components such as the root, upper parts, or the whole plant. The mode of application may result in local or systemic activity, via oral, injectable, or topical preparations.7 This lack of standardization hinders attempts to assess efficacy definitively.
Oral preparations include a tincture (made with alcohol or myrrh), freeze-dried extract in tablet form, capsules, and teas. No information is available regarding comparability of the bioavailability of active ingredients in these various preparations.
Adverse Events and Contraindications
Few serious adverse events associated with echinacea have been reported. Commonly reported side effects have included gastrointestinal symptoms such as nausea, diarrhea, and constipation. In addition, skin rash has been reported when used topically. Relatively little information exists in the literature regarding toxicity or drug interactions with echinacea.15
Echinacea has no known mutagenic properties.1 Of concern, however, are life-threatening episodes of anaphylaxis, as well as acute asthma, urticaria, and angioedema reported in association with echinacea use.16,17 Unpublished case reports presented at the American Academy of Allergy, Asthma and Immunology annual meeting in March 2000 suggest that allergic reactions to echinacea may result from IgE-mediated hypersensitivity, and may be more common in patients with atopy.16 Because of its immunomodulatory effects, echinacea generally is thought to be contraindicated for individuals with AIDS, HIV infection, or autoimmune disorders, although this contraindication has not been well established.12,18 In addition, individuals with allergies to members of the daisy family probably should avoid echinacea.19 Echinacea should be avoided in pregnant or lactating women because of a lack of information regarding safety.
Conclusion
Limited well-designed, controlled studies have evaluated the efficacy of echinacea as a cold remedy. A literature review revealed four controlled studies addressing this topic. Of these four, only one suggested utility of echinacea as a cold remedy, and this study used an
echinacea preparation containing a combination of other herbal ingredients. Very limited evidence suggests that echinacea may be useful for limiting severity and duration of cold symptoms after onset, but that it is not effective for preventing colds. Future research should devote particular attention to using a standardized, well-characterized echinacea preparation and should incorporate methods to ensure quality control.
Recommendation
Only a small number of controlled studies have evaluated the effectiveness of echinacea as a treatment for the common cold. Insufficient evidence exists for or against echinacea to recommend it as efficacious. Since there have been few reported side effects, and fewer therapeutic alternatives, it may be reasonable to encourage some interested patients to give it a try. Since echinacea has immunomodulatory effects, it cannot be recommended for individuals with allergies to the daisy family, autoimmune disorders, AIDS, or HIV infection; for pregnant or lactating women; or for patients with atopy.
Dr. Kattapong is a board-certified neurologist and a principal in MediCat Consulting, a health services consulting firm in Tucson, AZ.
References
1. Udani JK, Ofman JJ. Echinacea for the common cold. Altern Med Alert 1998;1:16-18.
2. Hobbs CR. The Echinacea Handbook. Portland, OR: Eclectic Medical Publications; 1989.
3. Foster S. Echinacea: Nature’s Immune Enhancer. Rochester, VT: Healing Arts Press; 1991.
4. Hartwell JL. Plants used against cancer. Lloydia 1969;32:153-205.
5. Blumenthal M. Herb market levels after five years of boom. HerbalGram 1999;47:64-65.
6. Bauer R, Wagner H. Echinacea: Handbuch fur Arzte, Apotheker und andere Naturwissenschaftler. Stuttgart, Germany: Wissenschaftliche Verlagsgesellschaft; 1990.
7. Grimm W, Muller, H. A randomized controlled trial of the effect of fluid extract of Echinacea purpurea on the incidence and severity of colds and respiratory infections. Am J Med 1999;106:138-143.
8. Turner RB, et al. Ineffectiveness of echinacea for prevention of experimental rhinovirus colds. Antimicrob Agents Chemother 2000;44:1708-1709.
9. Bauer VR, et al. Immunologic in vivo and in vitro studies on echinacea extracts [in German]. Arzneimittelforschung 1988;38:276-281.
10. Melchart D, et al. Echinacea root extracts for the prevention of upper respiratory tract infections: A double-blind, placebo-controlled randomized trial. Arch Fam Med 1998;7:541-545.
11. Henneicke-von Zepelin H, et al. Efficacy and safety of a fixed combination phytomedicine in the treatment of the common cold (acute viral respiratory tract infection): Results of a randomised, double blind, placebo controlled, multicentre study. Curr Med Res Opin 1999;15:214-227.
12. Blumenthal M, et al, eds. The Complete German Commission E Monographs. Austin, TX: American Botanical Council; 1998.
13. Giles JT, et al. Evaluation of echinacea for treatment of the common cold. Pharmacotherapy 2000;20:690-697.
14. Percival SS. Use of echinacea in medicine. Biochem Pharmacol 2000;60:155-158.
15. Borchers AT, et al. Inflammation and Native American medicine: The role of botanicals. Am J Clin Nutr 2000;72:339-347.
16. Today’s findings from the AAAAI annual meeting unveil new research on alternative therapies and food allergy: Echinacea can cause allergic reactions [press release]. Milwaukee, WI: American Academy of Allergy, Asthma and Immunology; March 7, 2000.
17. Mullins RJ. Echinacea-associated anaphylaxis. Med J Aust 1998;168:170-171.
18. Jellin J, ed. Natural Medicines Comprehensive Database. Stockton, CA: Therapeutic Research Center, Inc.; 1999.
19. Ertel G, McQueen CE. Echinacea purpurea and treatment of the common cold. Pharmacist’s Diet Suppl Alert 2000:1:4-7.
November 2000; Volume 3; 128-130
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