Black cohosh (Actaea racemosa)

Evidence from in vitro, animal and clinical studies suggests that black cohosh is a safe herbal therapy for menopausal women if taken for a limited period 2. Animal studies showed no evidence of oestrogenic effects on oestrogen-sensitive hormone levels, or changes in uterine weight or vaginal cell histology, and therefore, support the safety of use of black cohosh in oestrogen-sensitive cancer patients or in women for whom HRT is contraindicated 10. Clinical trials identified in this review did not report significant adverse effects in women with breast cancer using black cohosh extracts for 2 to 12 months 13 14 22. The minor adverse effects observed in clinical trials include nausea, vomiting, headaches, dizziness, mastalgia, and weight gain 20. No herb and drug interactions have been reported 20. However, black cohosh was found to alter the response to the agents commonly used to treat breast cancer in an experiment report using mouse breast cancer line 21. In this experiment, the black cohosh extracts increased the cytotoxicity of doxorubicin and docetaxel and decreased the cytotoxicity of cisplatin. Pre-existing liver damage is a contraindication.

In response of the "potential association" between black cohosh and hepatotoxicity, one systematic review by Dietary Supplement Information Expert Committee of the US Pharmacopeia's Council of Experts on the hepatotoxicity 23 found all the reports of liver damage were assigned possible causality, and none were probable or certain causality. The clinical pharmacokinetic and animal toxicological information did not reveal unfavourable information about black cohosh. Based on this safety review, the committee determined that black cohosh products should be labelled to include a cautionary statement. This is a change from the Expert Committee's decision of 2002, which required no such statement.

A systematic review 24 retrieved 13 clinical trials involving more than 2800 patients. All trials indicate relative safety: 97% of all the reported adverse effects were minor, and the only severe ones were not deemed to be related causally to black cohosh. Three postmarketing surveillance studies reported adverse effects in 0%, 12% only mild and transient, and 2% of patients, respectively. Four case series and 8 single case reports were identified: in most of them, no causal relationship was detected and only two case reports concluded a “possible” causality between serious safety problem and the black cohosh medication but without providing further details. The review concluded that a large body of preclinical and clinical studies suggests black cohosh to be relatively safe; however, many of these studies were of short duration. Case reports that suggest severe adverse effects demanded further attention.