St. John's Wort

Derived from the aerial parts of the plant, St. John's wort generally is used for depression, seasonal affective disorder, and anxiety. Products currently are standardized based on hypericin content, although the hyperforin and bioflavonoid contents are also believed responsible for activity. St. John's wort is metabolized primarily by the liver.

Some studies comparing St. John's wort to standard antidepressants suggest that it may be as effective as imipramine or selective serotonin reuptake inhibitors (SSRIs) to treat mild to moderate depression. Results from another clinical trial indicate that the effectiveness of St. John's wort is comparable to paroxetine, an SSRI, in the treatment of moderate to severe depression and is well tolerated. But a meta-analysis shows that data are inconsistent. Studies also show possible efficacy in the management of anxiety and premenstrual syndrome, although additional research is necessary.

St. John's wort can interact with many medications owing to induction of cytochrome P-450 3A4 and other mechanisms. Significant interactions include decreased efficacy of antiretrovirals, cyclosporine, tacrolimus, antiepileptics, irinotecan, and other chemotherapeutic agents. Serotonin syndrome may occur when St. John's wort is combined with antidepressants, sympathomimetics, or triptans.

Frequently reported adverse events include nausea, headache, constipation, dizziness, confusion, fatigue, and dry mouth. St. John's wort should be used under medical supervision.

J Soc Integr Oncol. 2006 Winter;4(1):52-5.