Interaction of St. John's Wort with oral contraceptives: effects on the pharmacokinetics of norethindrone and ethinyl estradiol, ovarian activity and breakthrough bleeding

St. John's Wort is associated with increased metabolism of norethindrone and ethinyl estradiol, breakthrough bleeding, follicle growth and ovulation. Women using OCs should be cautioned that St. John's Wort might interfere with contraceptive effectiveness.