Drug Profile

Background

Black cohosh is a plant belonging to the buttercup family and has the botanical names Actaea racemosa and Cimicifuga racemosa. It also goes by the popular names snakeroot, rattleroot, and bugbane. The ingredients for dietary supplements are chemically extracted from the roots and rhizome.

Black cohosh is native to North America and was routinely used by Penobscot, Winnebago, and Dakota Indians for coughs, colds, rheumatism, and to increase milk production.[1] In the 19th century, black cohosh enjoyed popularity as an ingredient in a 36-proof patent medicine called Lydia Pinkham’s Vegetable Compound.[2] Currently, “alternative” practitioners and some physicians prescribe black cohosh for hot flashes and other symptoms associated with menopause.

Claimed Uses

Menopausal Symptoms

The interest in black cohosh for menopausal symptoms relies in large part on the claim that the root has estrogen-like activity. However, there are conflicting studies on this issue, with recent studies usually not detecting such activity.[3]

The use of black cohosh received a boost when a committee of the American Collegeof Obstetricians and Gynecologists reported in 2001 that it “may be helpful in the short-term ([up to] 6 months) treatment of [certain menopausal] symptoms.”[4] This conclusion was, in the College’s own description, “based primarily on consensus and expert opinion”; they did not cite a single randomized controlled trial to support that statement.

We identified four randomized, placebo-controlled studies of the effectiveness of black cohosh for menopausal symptoms. In the first, black cohosh had no impact upon the number or intensity of hot flashes in breast cancer patients over a two-month period.[5] Based on this study, a 1987 German study, and two randomized studies that did not have placebo groups, the National Center for Complementary and Alternative Medicine of the National Institutes of Health concluded in a 2003 report that “the currently available data are not sufficient to support a recommendation on the use of black cohosh for menopausal symptoms.”[3]

We have identified three subsequent randomized, placebo-controlled studies of black cohosh for menopausal or menstrual symptoms that claimed some positive effects. In the first, black cohosh combined with two other drugs was studied to assess its effect on menstrual migraine. Consequently, the independent effect of black cohosh cannot be determined.[6] In the second, a study of hot flashes in breast cancer patients, the investigators and the patients knew who was getting black cohosh and who placebo; this can lead to bias, making study interpretation unreliable.[7] Finally, a study of the impact of black cohosh upon menopausal symptoms and bone markers was hampered by the exclusion of about one-third of the patients.[8] The latter two articles appeared in a medical journal supplement devoted almost entirely to black cohosh and sponsored by two of the herb’s manufacturers. Supplements to medical journals often have promotional attributes and may not be peer-reviewed.[9]

In 2006, a randomized controlled trial compared several herbal supplement regimens over a period of 12 months and included 351 women ages 45 to 55 years who were approaching menopause. The results of this large trial, called the Herbal ALTernatives for Menopause Study (HALT), were published in the December 19, 2006, Annals of Internal Medicine. The researchers concluded that:

Black cohosh used in isolation, or as part of a multibotanical regimen, shows little potential as an important therapy for relief of vasomotor symptoms [change of the size of blood vessels responsible for hot flashes].[10]

There are inadequate data to support the claims for black cohosh’s effectiveness in relieving the symptoms of menopause. Preparations tend not to be standardized, and one brand has been the subject of almost all the clinical trials. No tenable mode of action for the herb has been put forward.

The Australian equivalent of the Food and Drug Administration (FDA) reported in the April 2006 issue of the Australian Adverse Drug Reactions Bulletin that 49 cases of liver toxicity worldwide have been associated with the use of the dietary supplement black cohosh.  

Of the 49 suspected cases of liver toxicity known to the Australian regulators, patients experienced liver failure that required a liver transplant in four cases. Serious cases of liver toxicity have occurred with the use of black cohosh for less than a month.[11]

The January 2009 Drug and Therapeutics Bulletin reviewed black cohosh and other herbal and dietary supplements that are used to treat the symptoms of menopause. The journal found that women should not use these supplements to ease the symptoms of menopause because the products are not effective and many can cause dangerous side effects. The products also have the potential to interact dangerously with other drugs or herbal supplements.

Short-term post-marketing studies of black cohosh have revealed that mild, short-lasting side effects such as headache, dizziness and gastrointestinal complaints have been reported, although the rates of unwanted side effects with black cohosh in randomized controlled trials were similar to those with a placebo.

Serious cases of liver toxicity have even occurred when patients have used the supplement for less than a month. This includes symptoms such as yellowing of the skin and eyes, severe upper stomach pain with nausea and vomiting and loss of appetite.[12]

Interactions with Other Drugs

Black cohosh has not been reported to interact with any drugs, but this has not been specifically studied.[3]

Adverse Effects

Adverse effects of black cohosh include stomach upset, weight gain, and headache. There are two reports in the published medical literature of liver transplants associated with the use of black cohosh.[13],[14] In a randomized trial of black cohosh in rats, the supplement did not cause an increase in the rate of breast tumors, but if tumors did occur, they were more likely to have spread to the lungs in animals receiving black cohosh.[15] The National Center for Complementary and Alternative Medicine has warned about the use of black cohosh in pregnancy and by breast cancer patients.[3]

Conclusion

There is no significant evidence that black cohosh alleviates menopausal symptoms. A 12-month, randomized, placebo-controlled trial sponsored by the National Institutes of Health is currently under way but has not yet reported results.