OBJECTIVES. To review the evidence regarding the effectiveness of orally ingested Echinacea extracts in reducing the incidence, severity, or duration of acute upper respiratory infections (URIs).
SEARCH STRATEGIES. Information from a wide range of sources was used as background material. More than 100 articles, books, and book chapters were reviewed for content and further references. Database searches, bibliographic reviews, and conversations with experts were carried out iteratively from January 1997 to February 1999.
SELECTION CRITERIA. Published or unpublished reports of all blinded placebo-controlled randomized trials of any Echinacea formulation used as a treatment or for the prevention of URIs.
DATA COLLECTION AND ANALYSIS. Review considerations included randomization, blinding, power, validity and clinical relevance of outcome measurements, inclusion and exclusion criteria, indistinguishability of treatment and placebo, and appropriateness of conclusions for the data presented.
MAIN RESULTS. Nine treatment trials and 4 prevention trials fitting the selection criteria were found. Eight of the treatment trials reported generally positive results, and 3 of the prevention trials reported marginal benefit. Methodologic quality of the majority of the trials was modest.
CONCLUSIONS. Evidence from published trials suggests that Echinacea may be beneficial for the early treatment of acute URIs. The influence of publication bias on those results is unknown. Echinacea preparations vary widely in composition, and are often found in combination with other potentially active constituents, making specific dose recommendations problematic. There is very little evidence supporting the prolonged use of Echinacea for the prevention of URIs.
KEY WORDS. Plant extracts; medicine, herbal; respiratory tract infections; botanicals; phytomedicine. (J Fam Pract 1999; 48:628-635)
CLINICAL QUESTION Are orally ingested Echinacea extracts effective in reducing the incidence, severity, or duration of acute upper respiratory infections?
Upper respiratory infection (URI), usually viral, with its common variants rhinosinusitis and pharyngitis, is the highest-incidence acute illness in the developed world.[1-3] According to estimates, the average adult in the United States has 2 to 4 colds per year; the average schoolchild has 6 to 10. Although patients with complications, such as bacterial sinusitis, otitis media, streptococcal pharyngitis, bronchospasm, or pneumonia may benefit from antibiotic or inhaler treatment, medical science has little to offer for uncomplicated infections.[5-10] Nevertheless, antibiotics are frequently prescribed, despite convincing evidence of little or no benefit.[11-17] Clearly, there is great need for effective, safe, and affordable treatment.
Botanical extracts from plants of the genus Echinacea are among the most widely used herbal medicines throughout Europe and North America and are most commonly used for the prevention or treatment of URIs. Echinacea extracts are believed to affect URIs through "immunostimulating" activity. Symptom reduction through immunomodulation holds some theoretical and empirical promise.[18,19] If effective, such treatment could have an impact on the morbidity and loss of productivity associated with URIs, and the overuse of antibiotics and the effects of their sequelae in terms of costs, adverse effects, and antibiotic resistance.
Echinacea was first used by Native Americans as a remedy for a wide variety of illnesses. It was mentioned in the Flora Virginica in 1762, the Eclectic Dispensatory of...