Interactions with St. Johns Wort and Echinacea

Division of Clinical Pharmacology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, U.S.A. 

John s wort (Hypericum perforatum) is a perennial wildflower indigenous to Europe, North Africa, and western Asia (Fig. 1) and has been used for medicinal purposes for over two millennia. As far back as the early 16th century, St. John s wort was used primarily to treat anxiety, depression, and sleep disorders. In the late 20th and early 21st century, St. John s wort has been recommended for the treatment of mild to moderate depression (7). In support of its use for the treatment of mild to moderate depression, a number of clinical trials have demonstrated that St. John s wort has comparable efficacy to the tricyclic antidepressants (i.e., imipramine) and selective serotonin reuptake inhibitors (e.g., fluoxetine and paroxetine) (8-13). 

It should be noted that these clinical trials are typically conducted within a short time period and thus may not reflect long-term outcomes. The utility of St. John s wort in the treatment of moderate to severe depression has been investigated (14-17) in large randomized placebo-controlled multi-institutional studies. Some such studies demonstrated efficacy (16), but others failed to detect a clinically significant effect on the symptoms of the moderate to severely depressed individuals (15,17). Gelenberg et al. demonstrated a relapse rate of approximately 30% in moderate to severely depressed individuals who initially responded to St. John s wort therapy as would be expected from experience with prescription antidepressants (14). 

John s wort and some individual constituents of the preparations have been administered orally, topically, and intravenously in various pharmaceutical formulations, including tinctures, teas, capsules, purified components, and tablets. These botanical preparations of St. John s wort are prepared from plant components (i.e., flowers, buds, and stalk) whose content of the wide array of structurally diverse bioactive constituents may differ (Table 1 and Fig. 2). Many commercial tablet and capsule formulations of St. John s wort are standardized using the ultraviolet absorbance of the naphtho-dianthrones, hypericin, and pseudohypericin, to contain 0.3% hypericin content. Thus, a 300 mg dose of St. John s wort contains approximately 900 pg hypericin per dose. Despite the standardization of dosage forms 

Biochemical class Plant source Active constituent 

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