St. John's Wort May Not Curb OC Effectiveness


LOS ANGELES — St. John's wort does not appear to interfere with the antiandrogenic effects of oral contraceptive pills, Robin Fogle, M.D., said at the annual meeting of the Society for Gynecologic Investigation.

She said testosterone levels decreased, while a marker of androgen metabolism increased, in 15 healthy women treated with St. John's wort and Loestrin 1/20 (norethindrone/estradiol) in a 4-month study.

Although the changes did not reach statistical significance, the outcomes strongly suggest St. John's wort will not interfere with the pill's effects when used as a primary treatment for hirsutism, said Dr. Fogle, of the University of Southern California, Los Angeles, in an interview.

The study was undertaken because reports have shown the over-the-counter herbal remedy, commonly used for depression and inflammation, induces cytochrome P450 activity. This can interfere with the efficacy of some drugs, including oral contraceptives, Dr. Fogle and her coinvestigators wrote in a poster presented at the meeting.

None of the women in the study had hirsutism. They took Loestrin 1/20 for four consecutive 28-day cycles. During the last two cycles, the protocol added 300 mg of St. John's wort taken three times daily.

Mean testosterone fell 10.7% (from 44.8 ng/dL to 40.0 ng/dL), and free testosterone fell 15.8% (from 0.38 ng/dL to 0.32 ng/dL) after the addition of St. John's wort. Conversely, 3α-androstanediol glucuronide, the marker of androgen metabolism, rose 6.5% from 2 ng/mL to 2.13 ng/mL.

“It appears that St. John's wort enhances androgen metabolism and does not interfere with the antiandrogenic properties of oral contraceptive pills,” they said.

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