Echinacea: Recommendations for its Use in Prophylaxis and Treatment of Respiratory Tract Infections

Abstract

Abstract Products containing Echinacea are some of the best selling and most widely used botanical dietary supplements in the United States. Commercial Echinacea extracts are manufactured primarily from 3 Echinacea species, namely Echinacea purpurea (herb, roots, or seeds), E. angustifolia (roots), and E. pallida (roots). Current recommendations for use of these products include oral administration for the prophylaxis and treatment of the common cold, bronchitis, influenza, and bacterial and viral infections of the respiratory tract.Unfortunately, much of the clinical data published prior to 1991 suffered from poor methodology and, therefore, was difficult to assess. However, more recent controlled clinical trials have suggested that while Echinacea may not be effective for the prophylaxis of upper respiratory tract infections, these products may be useful in decreasing the symptoms and duration of illness. In vitro and in vivo studies indicate that the therapeutic effects of Echinacea are due to a stimulation of cellular immune response. The major adverse events reported are allergic reactions, ranging from contact dermatitis to anaphylaxis. Patients with an allergy to plants in the daisy family (Asteraceae) should be instructed not to use products containing Echinacea. No drug interactions have been reported, however, the extracts have been shown to inhibit the activity of cytochrome P450 and, therefore, have the potential to influence drug metabolism. Echinacea‐containing dietary supplements may be used safely in conjunction with antibiotics or sulfa drugs. According to the German Commission E, patients with autoimmune disorders, AIDS, HIV infection, or tuberculosis should not use Echinacea, however, there is little scientific data to substantiate these contraindications.Recommendations for oral dosage and dosage forms are difficult due to the wide variety of preparations and doses used in the clinical trials. However, based on existing data products containing pressed juice or hydroalcoholic extracts, Echinacea purpurea (leaf juice and roots) and E. pallida (roots) have the most convincing data supporting their use.