St. John's wort might reduce the effectiveness of oral contraceptives

There are growing concerns that St. John's wort might reduce the effectiveness of oral contraceptives.

So far there are reports of breakthrough bleeding and menstrual irregularities in women who combine St. John's wort and the pill. These are signs of decreased estrogen levels.

St. John's wort appears to induce cytochrome P450 3A4...which increases the metabolism of ethinyl estradiol.

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