Potential for Drug interactions with St. John’s wort

• Combination with MAOIs can cause serotonergic crises.

• Just this past week, a couple of case reports have come out of pts, who were on immunosuppressive agent cyclosporin for cardiac transplants, who went in rejection bc they took St. John’s wort. St. John’s wort apparently acts on the cytochrome P450 system to induce CYP3A4 enzymes, which decreases levels of cyclosporin; thus, the pt begins to reject their organ.

• A similar phenomenon was noted by a group from the NIH in HIV pts on protease inhibitors. Bc of the induction of enzymes by St. John’s wort, the levels of the protease inhibitors decrease, which increases the risk in those pts to develop a lack of response of the HIV to protease inhibitors and the potential for developing resistance.

• It also induces the intestinal drug transporter P-glycoprotein and decreases levels of digoxin.

So, we must ask pts what OTC drugs and herbal medications they are taking; huge complications can arise if we don’t know.

Category: Pharmacology Notes