Black cohosh could interfere with anticancer drugs

Black cohosh, or Actea racemosa, is a plant native to North America, the roots and rhizomes of which have been used for centuries to alleviate menopausal symptoms such as hot flashes and mood swings. Although several opinions have been put forward, scientists have yet to agree on which active compound or compounds are responsible for its therapeutic properties.

According to lead researcher Sara Rockwell, professor of Therapeutic Radiology and Pharmacology at Yale School of Medicine, combining mainstream therapies with complementary and alternative medicine is common practice amongst cancer patients. But as many do not tell their physician, they are not alerted to possible interactions with drugs.

Rockwell carried out tests to determine the effect that black cohosh may have on the way cells respond to drugs commonly used to treat breast cancer, using a widely studied mouse breast cancer cell line in culture. The dose was obtained by extrapolating the dose recommended from the labels on the commercially available black cohosh products used, so as to produce the same concentration of extract in cell culture medium.

The results were published in the April issue of Breast Cancer Research and Treatment​.

Black cohosh was seen to increase cytotoxicity (cell killing) by two of the drugs, doxorubicin and docetaxel. It decreased the cytotoxicity of cisplatin.

No change in effect was seen in a fourth drug, 4-hydroperoxycyclophosphamide (4-HC), nor in radiation therapy.

From this study Rockwell was not able to extrapolate why each agent responded differently, nor assess the relative potential for risks and benefits of using the herb to cancer patients.

But she said: "Our studies caution that black cohosh should not be considered to be a harmless herb that is inconsequential to the health of cancer patients or to the outcome of conventional cancer therapy."​

Rockwell told NutraIngredients-USA.com that the next stage in her investigations will look at the extracts' impact on the anti-tumor effects of the drugs and radiation. She also plans to assess how black cohosh affects the drugs' and radiation's toxicities to the healthy normal tissues, that limit the intensity of the treatment that can be given to cancer patients.

These studies will use mice fed the black cohosh extracts in their drinking water, at doses based on the doses recommended to women on the labels of commercial black cohosh extracts.