St. John's Wort Interactions

Why this herb is singled out

NIH says it has been clearly shown that St. John's wort can interact in dangerous, sometimes life-threatening ways with a variety of medicines. [1] For most adults who take no medicine it appears safe for up to 12 weeks. [1]

What it does

St. John's wort speeds up the processes that turn drugs into inactive substances, so affected medicines can work less well. [2]

Medicines affected (from NIH)

• Some antidepressants including amitriptyline and bupropion; with certain antidepressants or other drugs that affect serotonin, serotonin-related side effects can be serious. [1]
• Cyclosporine (transplant). [1]
• Digoxin and ivabradine, indinavir and nevirapine (HIV), irinotecan and imatinib (cancer), warfarin and certain statins including simvastatin. [2]
• Birth control pills, and medicines for HIV/AIDS, heart disease, depression and organ transplants, are less effective. [3]
• Over-the-counter fexofenadine (Allegra). [4]

Other safety points

• Large oral doses or topical use might cause severe skin reactions after sun exposure; other side effects can include diarrhea, dizziness, trouble sleeping, restlessness and skin tingling. [1]
• Pregnancy: may be unsafe, with a possible increased risk of birth defects; breastfed infants of mothers taking it can have colic, drowsiness and lethargy. [1]
• Tell your providers if you use it. [1]

What to do

Do not start St. John's wort, or stop it suddenly, without asking your prescriber or pharmacist. See the plant guide: St. John's wort.