January 2011 in “Reactions Weekly” St. John's Wort may reduce the effectiveness of finasteride by increasing its breakdown in the body.
St. John’s wort changes how finasteride works in the body, possibly affecting its effectiveness.
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November 2008 in “European Journal of Pharmaceutical Sciences” This study found that St. John's wort treatment for two weeks induced finasteride metabolism and reduced its plasma exposure in healthy men.