If I recall correctly, St John's Wort (or more accurately, some components of St John's Wort) are substrates for the Pregnane X-receptor (also called PXR). Apparently, hitting this receptor with agonist activity, as does St Johns wort, can induce the Cyp 3A4 metabolizing enzyme, which is an enzyme involved in the metabolism of like 50% or more of drugs. Thus, it is true that St John's Wort can increase metabolism of other drugs. This has been particulalrly warned about with oral contraceptive use and certain anti-HIV drugs, though it is likely it would affect many other drugs as well. St Johns wort also can sensitize the user to sunlight and excess exposure to the sun should be avoided while taking this drug. Although the mechanism of St John's wort is
nov completely clear, some warn against using with other antidepressants such as SSRIs (Prozac, paxil, zoloft, etc) and others since apparently one can see enhanced activity of the drugs due to the possibility of St Johns wort inhibiting the MAO enzymes which are responsible for metabolism of the SSRIs. If they are combined, clearly one should use less than a full dose of each, at least initially. Despite the forgoing, St Johns wort is one of the better established herbal remedies having demonstrated considerable efficacy in numerous clinical trials. It appears that St Johns wort at 900 mg of 0.3% hypericin standarized is the equal of most prescription SSRIs, possibly with reduced side effects. SSRIs are notoriously well known for sexual side effects, among other things. If one does not have drug interactions to worry about, then St Johns wort appears to be a pretty good product, it is very popular in Europe, particularly in Germany. I have used it on and off and like you, liked it quite a bit! Good luck!