St. John's Wort (hypericum) is used for depression or anxiety that leads to fatigue and adrenal gland exhaustion. It appears to work at least in part as an SRI (Serotonin Reuptake Inhibitor). Combining an SRI with an MAO inhibitor can produce a dangerous rise in blood pressure; after stopping use of MAO inhibitors, one should wait four weeks before taking any SRIs. This caution is not based on specific medical research on hypericum and MAO inhibitors, but on what is known about prescription SRIs and MAO inhibitors. Until further research is done on how and why hypericum works to alleviate the symptoms of depression, hypericum should be considered an SRI and treated accordingly.
St John's wort has been used for so-called 'nervous disorders' for a couple of thousand years. It is sold over the counter, usually in tablet form, and is also supplied by complementary practitioners such as naturopaths and herbalists.
The balance of evidence suggests that if St John's wort is taken at a sufficiently high dose, it is as effective as pharmaceutical antidepressants for mild, and possibly moderate, depression. However, it is unlikely to benefit people with more severe depression. The dosage of St. John's Wort that has been used in most studies is a 900mg daily dose taken in 300mg increments TID. The typical preparation is a 0.3% extract of hypericin). Results may not be seen for at least four to six weeks. Discontinue use after six weeks if you've noticed no results because it's probably not effective for you.
The benefit of St John's wort is that it has fewer side effects than prescription antidepressants (though it can cause drowsiness, headaches or a photosensitivity to sunlight in some individuals). Like the pharmaceuticals, it can cause serotonin syndrome, and it has recently been discovered that St John's wort can interfere with other medicines, including anti-HIV drugs, immunosuppressants, warfarin, and potentially others, including the oral contraceptive pill. For this reason it is important to talk to a GP before taking St John's wort, and anyone seeing a herbalist or naturopath should also tell them what other medicines they are taking.
In 2003, laboratory testing of 54 commercial St JohnĻs wort products from Canada and the United States found only two products with a total hypericin content within 10% of the amount stated on the label. On average, most products tested contained half of the labeled amount of hypericin. [Can J Clin Pharmcol 2003;10(3): pp.114-8]
Fourteen days of supplementation with a St. John's wort extract (300mg TID) induced cytochrome P450 3A4 (CYP 3A4) enzyme activity in a crossover study of 12 healthy adults. The investigators concluded that St. John's wort may diminish the clinical effectiveness or increase dosing requirements for all CYP 3A4 substrate drugs, which represent at least 50% of all marketed medications. [JAMA 2003;290(11): pp.1500-4]