Echinacea purpurea for Prevention of Experimental Rhinovirus Colds

Abstract

A randomized, double-blind, placebo-controlled clinical trial was conducted to evaluate the ability of Echinacea purpurea to prevent infection with rhinovirus type 39 (RV-39). Forty-eight previously healthy adults received echinacea or placebo, 2.5 mL 3 times per day, for 7 days before and 7 days after intranasal inoculation with RV-39. Symptoms were assessed to evaluate clinical illness. Viral culture and serologic studies were performed to evaluate the presence of rhinovirus infection. A total of 92% of echinacea recipients and 95% of placebo recipients were infected. Colds developed in 58% of echinacea recipients and 82% of placebo recipients (P=.114, by Fisher's exact test). Administration of echinacea before and after exposure to rhinovirus did not decrease the rate of infection; however, because of the small sample size, statistical hypothesis testing had relatively poor power to detect statistically significant differences in the frequency and severity of illness.

Echinacea species (Echinacea angustifolia (DC.) Hell., Echinacea pallida (Nutt.) Nutt., Echinacea purpurea (L.) Moench): a review of their chemistry, pharmacology and clinical properties

“…Thus, the results indicate that, in this study, echinacea was no more effective than placebo in preventing rhinovirus infection. However, it is possible that the study did not have sufficient statistical power to detect a difference between the two groups (Sperber et al 2004).…”

“…Several new trials of echinacea preparations in the prevention of the common cold have been completed since the Cochrane review, but most have not shown beneficial effects for echinacea preparations compared with placebo on main outcome measures (Melchart et al 1998;Grimm & Mu¨ller 1999;Turner et al 2000;Cohen et al 2004;Sperber et al 2004).…”

“…Two further studies have tested the effects of echinacea preparations for the prevention of colds due to experimental rhinovirus infection (Turner et al 2000;Sperber et al 2004). In one study, adult volunteers (n ¼ 117 enrolled) with a serum titre of neutralizing antibody to rhinovirus of 1:4 received echinacea (300 mg) or placebo three times daily for 14 days before and for 5 days after challenge with rhinovirus (n ¼ 92 challenged due to study withdrawals).…”

“…In a subsequent study (Sperber et al 2004), a randomized, double-blind trial, 48 healthy adults received a preparation containing the pressed juice of the aerial parts of E. purpurea in a 22% alcohol base (EchinaGuard) 2.5 mL three times daily, or placebo, for 7 days before and after inoculation with rhinovirus (RV-39) by intranasal administration in two inocula about 30 min apart (total dose 0.25 mL per nostril). The proportions (95% CI) of participants with laboratory evidence of infection (at least a 4-fold increase in RV-39 neutralizing antibody titre and/or recovery of rhinovirus on viral culture), the primary outcome measure, were 92% (95% CI 73-99) and 96% (95% CI 77-100) for echinacea recipients and placebo recipients, respectively, and with clinical illness (presence of a cold defined as a 5-day total symptom score of 5 or more and 3 successive days of rhinorrhea or participant's positive self-report of a cold) 58% (95% CI 37-78) and 82% (95% CI 60-94) for the echinacea and placebo groups, respectively (P ¼ 0.114).…”

Herbal Medicine for Cough: a Systematic Review and Meta-Analysis

“…We found 8 studies exploring the use of a varied range of solid and liquid Echinacea preparations in the treatment of cough symptoms for common cold or URTI [16,41,42,43,44,45,46,47]. A total of 1,130 patients were enrolled in these studies, with an average of 141 patients per study.…”