St. John's Wort is a CYP3A4 Inducer

Recent work suggests that St. John's wort (SJW), a popular, self-prescribed herbal remedy for depression, may also have antiretroviral properties. To study the effect of SJW on cytochrome P450 3A4 (CYP3A4) activity, these investigators measured levels of cortisol (which is metabolized by CYP3A4) in 13 healthy individuals taking standard doses of SJW (300 mg standardized to 0.3 percent hypericin, three times a day). The results suggest that the pharmacology of SJW is not different from that of prescription medications.

To control for the circadian variation of cortisol metabolism, investigators used the ratio of 24-hour excretion of urinary 6-β-hydroxycortisol to cortisol. The ratio increased by 114 percent between baseline and day 15 of SJW …