Does St. John’s Wort Impair the Pill’s Efficacy?

In this clinical trial funded by the National Center for Complementary and Alternative Medicine, investigators examined the interaction between St. John’s wort and oral contraceptives . . .

In this clinical trial funded by the National Center for Complementary and Alternative Medicine, investigators examined the interaction between St. John’s wort and oral contraceptives (OCs) in 16 women (mean age, 26; mean BMI, 22.5; 69% white). The women were followed for 4 menstrual cycles: During cycles 1 and 2, they took placebo plus a monophasic OC (21 days of ethinyl estradiol/norethindrone acetate [20 μg/1 mg], followed by 7 days of placebo), and during cycles 3 and 4, they took St. John’s wort (300 mg 3 times daily) plus the OC. The women were blinded to the sequence of active medication and placebo; condoms were provided as backup birth control.

Pharmacokinetic analyses, performed during cycles 2 and 4, suggested that St. John’s wort…

Author

Andrew M. Kaunitz, MD