CAM InteractionsSt. John's Wort

St. John’s wort drug interactions

In a pharmacy continuing education newsletter (InetCE 221-999-05-056-H01), Dr. Mary Chavez states, “St. John’s wort is the most studied herbal, and has the most evidence for significant interactions with medications.”

From her article, documented herbal-drug interactions based on reliable case reports, case series, or clinical investigations are presented below. I listed only generic drug names. A useful link to identify brand names from generic names is found here. Dr. Chavez includes more detailed information in the newsletter.

When taken with St John’s wort the effects of the following drugs decrease: alprazolam, amitriptyline, chlorzoxazone, cyclosporine, digoxin, fenoxfenadine, imatinib, indinavir, irinotecan, mephytoin, nevirapine, omeprazole, oral contraceptives, phenprocoumon, ritonavior, rosiglitazone, simvastatin, tacrolimus, theophylline, venlafaxine, verapamil, voriconazole, warfarin.

When taken with St John’s wort the effects of the following drugs increase, with the risk of toxicity: buspirone, loperamide, methadone, nefazodone, paroxetine, sertraline, trazodone, trazodone.

Dr. Chavez concludes, “Pharmacists and other healthcare providers must take an active role in learning about herbals and other dietary supplements to make informed decisions.” Actually, consumers taking St John’s wort will benefit from this article as well. Table 4 is worth the time to download and match the herbal medicine you are taking (she lists 18 herbals) to prescription drugs in order to see if there is a potential interaction.

To read the article, go here and then click the PDF icon next to the title “Herbal-Drug Interactions”.

6/30/06 22:49 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.