Black cohosh may make breast cancer drug more toxic

April 9, 2003 in Nutrition Topics in the News, Vitamins, Minerals, Supplements, Women's Health

Black cohosh may make breast cancer drug more toxic

Women with breast cancer who are undergoing chemotherapy may want to avoid black cohosh, the herbal remedy often used to treat menopausal symptoms such as hot flashes, according to Connecticut researchers from the Yale University School of Medicine.

In a new study of laboratory-grown breast cancer cells, the herb seemed to increase the toxicity of the commonly used chemotherapy drugs doxorubicin (Adriamycin) and docetaxel (Taxotere), but not a third, cisplatin.

This was observed with three different commercial black cohosh extracts. The suggestion that black cohosh may make these anticancer drugs more potent than they already are could be "a good thing or a bad thing," the researchers said.

If this were an effect just on the tumor cells, that would be a good thing because it would mean you get more anti-tumor effect for a person on black cohosh. On the other hand, Adriamycin is used in doses that are nearly toxic - it wipes out the bone marrow and is very close to the limit of heart toxicity. A substantial number of patients treated with Adriamycin show serious heart injury after treatment and if black cohosh increased that it could make this drug lethal.

More research is needed to determine if this is true for patients -- results in laboratory cells may not mimic what happens in the body, a much more complex situation compared with a carefully controlled experiment.

Rockwell's team focused their studies on black cohosh because they noticed that many women who went off hormone replacement therapy (HRT) when they were diagnosed with breast cancer began taking this particular herb during chemotherapy and radiation therapy. Many women assume that black cohosh is a safe and effective natural remedy for menopausal symptoms. But how it interacts with other drugs is unclear.

The herbal remedy did not influence laboratory-grown breast cancer cells in the absence of chemotherapy drugs, or affect the growth of breast cancer tumors in mice fed the herbal remedy.

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