A study published in the June 2014 issue of the Journal of Complementary and Alternative Medicine disclosed that in 28% of the cases when St. John's Wort was used there was the potential for harmful combinations when combined with pharmaceutical drugs. Apparently SJW induces accelerated detoxification of the same pathways in the liver as are used by birth control pills, Coumadin, many chemotherapies, and blood pressure medications. This would lower serum levels of these drugs and lead to potentially less pharmacological effect and lessened effectiveness for these drugs.
This information is important and should be considered in clinical practice. In fact, we should be aware of the effects of all supplements and herbs when they are combined with drugs or for that matter, with other supplements and herbs as well. The place where this kind of thinking is most important is when combining different pharmaceutical drugs! We have almost no data on this, yet we continue to boldly mix and match different drugs routinely in conventional medical practice.
There is a clear double standard that favors pharmaceutical usage.