The biggest problem with St. John's wort is that it interferes with lots of other medicines.[5] [6] [7] For example, you shouldn't take St. John's wort if you are taking:[8]
* The contraceptive pill. St. John's wort makes the pill less effective, so there is a higher chance you'll get pregnant
* A drug called simvastatin (brand name Zocor). This is a medicine used to treat or prevent high cholesterol and heart disease.
* Drugs for migraine called triptans, such as sumatriptan (brand name Imigran) and eletriptan (brand name Relpax)
* Drugs for epilepsy
* Warfarin, and similar drugs used to prevent blood clots
* A drug for eczema called tacrolimus (brand name Protopic)
* Drugs for HIV called indinavir, efavirenz and nevirapine
* Antidepressants.