A mother in your practice asks about using echinacea for the prevention of upper respiratory tract infections (URTIs) for her children, aged two and five years, who are otherwise healthy children. She is very pleasant and has been compliant with therapy in the past.
WHAT DO YOU RECOMMEND?
Complimentary and alternative medicine treatments are commonly used by Canadian patients and by parents for their children. In the context of chronic illness, this appears to be the rule rather than the exception. Echinacea is consistently one of the most commonly used herbal medications in North America, frequently used by patients for the prevention and therapy of URTIs.
DOES IT WORK?
Echinacea, or the purple cone flower, is a plant of which three species are used medicinally. The constituents are known to vary between the three species. A variety of preparations, including extracts, roots, aerial parts and rhizomes, have been used for prophylaxis and therapy.
Although the impression is that there is little research in complimentary and alternative medicine, there are two recent large reviews on echinacea (1,2). Barrett et al (1) reviewed 13 trials that used echinacea for URTIs – nine that used echinacea as therapy and four prevention trials. There were considerable differences among the trials in terms of products used and outcome measures, and, consequently, it was not possible to conduct a meta-analysis. Eight of the nine treatment trials reported benefit from echinacea therapy, and two of the prevention trials reported benefit while two did not (1). The Cochrane review by Melchart et al (2) analyzed the results of 16 trials using echinacea – eight as therapy for URTIs and eight for prevention – with a total of 3396 subjects studied. The prevention studies suggested that any beneficial effects of echinacea were small at best, with a maximum estimated risk reduction of 15% to 20%. In contrast, there was stronger evidence for benefit in the treatment trials (2).
In applying these data, one major consideration is that the majority of subjects studied were adults. Among the subjects reported in the trials evaluated in the Cochrane review, there were 1100 subjects aged one to 13 years (2). Unfortunately, these trials included the use of other natural health products, and the contribution of echinacea to the overall benefit demonstrated is difficult to evaluate. The treatment trials suggest that the benefits of echinacea in the context of URTIs in children are probably confined to treatment and not prevention. Echinacea appears to show benefits in the treatment of URTIs when it is given early, and this is related to the reduced progression of symptoms. An estimate of the number of children needed to treat to produce a benefit is five. This means that, on average, five children must be treated to see improvement in one child.
IS IT SAFE?
There has been extensive evaluation of echinacea in murine models, and it appears that the lethal dose when expressed as the median lethal dose (LD50) is many times the usual human dose (3). Echinacea is known to have the potential to generate an immune response, and allergic reactions have been reported. However, allergic reactions appear to be infrequent, with the Australian adverse events reporting system reporting 51 cases and the World Health Organization database reporting 76 cases over 19 years, with 10 hypersensitivity reactions and eight cases of anaphylaxis (4,5). The Australian data suggest a higher risk among atopic individuals (a known risk factor for adverse reactions to other drugs such as antibiotics). Fever has been reported with parenteral administration of echinacea, but the data to date suggest that oral administration of echinacea is unlikely to be associated with a significant risk for serious adverse events.
An important caveat applies. The data to date are largely based on otherwise healthy adults and children, and the possible adverse effects of echinacea in children with an altered immune system (eg, autoimmune disease or HIV) are not known. Because the reduced rate of progression of symptoms in the context of URTIs is presumably related to immune modulation, caution is recommended when planning to use echinacea in children who are not otherwise healthy.
Returning to our case, what do we recommend to the mother of the two children? The evidence to date does not support the use of echinacea in the prevention of URTIs and you should share this information with the mother of your patients. The evidence does suggest the potential that echinacea may reduce the severity of symptoms among children who have a URTI. The two provisos that apply are that therapy appears only to be effective if given early and that the data to date have come primarily from otherwise healthy children.
ACKNOWLEDGEMENTS
Dr Rieder holds the GSK-CIHR Chair in Paediatric Clinical Pharmacology at the University of Western Ontario. Dr Rieder’s research is supported by the Canadian Institutes of Health Research, the Robarts Research Institute and the Children’s Health Research Institute.
REFERENCES
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