Echinacea for upper respiratory infection

OBJECTIVES. To review the evidence regarding the effectiveness of orally in gested 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 bac kground material. More than 100 articles, books, and book chapters were rev iewed for content and further references. Database searches, bibliographic reviews, and conversations with experts were carried out iteratively from J anuary 1997 to February 1999. SELECTION CRITERIA. Published or unpublished reports of all blinded placebo -controlled randomized trials of any Echinacea formulation used as a treatm ent or for the prevention of URIs.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 pla cebo, and appropriateness of conclusions for the data presented. MAIN RESULTS. Nine treatment trials and 4 prevention trials fitting the sel ection criteria were found. Eight of the treatment trials reported generall y positive results, and 3 of the prevention trials reported marginal benefi t. 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 publicat ion bias on those results is unknown. Echinacea preparations vary widely in composition, and are often found in combination with other potentially act ive constituents, making specific dose recommendations problematic. There i s very little evidence supporting the prolonged use of Echinacea for the pr evention of URIs.