Safety and Efficacy Profile ofEchinacea purpureato Prevent Common Cold Episodes: A Randomized, Double-Blind, Placebo-Controlled Trial

Abstract

Objective. To investigate the safety (risk) and efficacy (benefit) ofEchinacea purpureaextract in the prevention of common cold episodes in a large population over a 4-month period.Methods. 755 healthy subjects were allocated to receive either an alcohol extract from freshly harvestedE. purpurea(95% herba and 5% root) or placebo. Participants were required to record adverse events and to rate cold-related issues in a diary throughout the investigation period. Nasal secretions were sampled at acute colds and screened for viruses.Results. A total of 293 adverse events occurred withEchinaceaand 306 with placebo treatment. Nine and 10% of participants experienced adverse events, which were at least possibly related to the study drug (adverse drug reactions). Thus, the safety ofEchinaceawas noninferior to placebo.Echinaceareduced the total number of cold episodes, cumulated episode days within the group, and pain-killer medicated episodes.Echinaceainhibited virally confirmed colds and especially prevented enveloped virus infections (P<0.05).Echinaceashowed maximal effects on recurrent infections, and preventive effects increased with therapy compliance and adherence to the protocol.Conclusions. Compliant prophylactic intake ofE. purpureaover a 4-month period appeared to provide a positive risk to benefit ratio.