Are There Interactions Between St. John's Wort And Tamoxifen?

Posting Date: 12/11/2000

Q: I work with breast cancer survivors. Many of the women are taking tamoxifen and will be doing so for at least five years.

Many of them also have problems with depression and have had relief using St. John's wort. Are you aware of any interactions between St. John's wort and tamoxifen?

A: We haven't seen any clinical studies proving that St. John's wort lowers circulating levels of tamoxifen. But based on what we know about the metabolism of these medicines, we suspect that is a strong possibility.

Until the research is done, we would discourage women on tamoxifen from taking St. John's wort. It might make this drug less effective and increase the risk of a cancer recurrence.

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