Uses and Benefits
Black cohosh is most commonly used for symptoms associated with menopause. Introduced into Germany in the 1950s, it has been actively promoted as an alternative to estrogen, since it is believed to have estrogen-like benefits without the unpleasant or harmful side effects. Black cohosh has been adopted for a variety of menstrual, menopausal, and reproductive maladies, and was an essential ingredient in Lydia Pinkham's Vegetable Compound, a popular patent remedy for "female complaints." The herb has also been used traditionally for rheumatism and inflammatory conditions.

Pharmacology:
Constituents include triterpene glycosides (thought to be markers of biologic activity), caffeic acid, and isoferulic acid. Remifemin, a proprietary extract standardized to the triterpene glycoside 27-deoxyactein, is the preparation most studied by German investigators. Other triterpene glycosides include actein and cimicifugoside.
Investigators have sought to determine whether black cohosh is a phytoestrogen, an herb that binds to estrogen receptors and has estrogenic properties but results are contradictory. Early animal studies found that black cohosh induced estrus and increased uterine weight in rats and mice, suggesting estrogenic effects. Methanol extracts of the herb were also reported to bind to estrogen receptors and to selectively reduce luteinizing hormone in animals. These extracts were thought to contain lormononetin, an isoflavone that binds to estrogen receptors. However, isoflavones are usually found in legumes (such as soybeans and red clover), not in plants related to black cohosh, and a recent study failed to find formononetin in commercial ethanol extracts such as Remifemin.
In several older studies in menopausal women, usual doses of Remifemin were associated with estrogen-like vaginal epithelial stimulation and reduced LH levels. However, results were confounded by lack of study blinding, small groups, or lack of baseline hormone measurements; more recent pharmacologic studies contradict these results. In a well-controlled animal study, commercial ethanolic black cohosh extracts did not produce estrogenic effects on the uteri or vagina of rats and mice. In a randomized, double-blind study in 152 menopausal women, daily doses of 40 mg or 127 mg of Remifemin for 6 months reportedly had no effect on LH, follicle stimulating hormone, sex hormone binding globulin, prolactin, estradiol, or vaginal cytology. A randomized double blind trial in women with breast cancer also found no effects on LH or follicle stimulating hormone (FSH) with 40 mg/day of Remifemin over 2 months. In addition, several in vitro studies of whole black cohosh extracts (including Remifenin) failed to demonstrate binding to, or stimulation of, estrogen receptors.

Clinical Trials:
Black cohosh was reported to benefit thousands of patients in early case series and uncontrolled studies.The benefits included relief from menopausal symptoms, menstrual irregularities, and other instabilities thought to be associated with "hormone imbalances." In the 1980s, there were six European trials of Remifemin that reported benefits for the treatment of menopausal symptoms using objective outcome measurement tools. However, only three studies were controlled, and only one of these was randomized and blinded.
In the only European double-blind, randomized, controlled trial (RCT), 80 menopausal women were randomized to 80 mg of Remifemin daily, 0.625 mg of conjugated estrogens for 21 days/month, or a placebo. After 12 weeks, the black cohosh preparation was statistically superior to both estrogen and placebo, as evaluated by a standardized symptom index (measuring hot flashes and other typical symptoms) and a separate standardized anxiety scale. Of the 16 patients who self-discontinued treatment, only one was from the black cohosh group, 12 were from the estrogen group (for "ineffectiveness"), and three were from the placebo group. Because estrogen had no more effect than placebo in this study, the results of this trial are questionable.
The other two controlled studies each included 60 women with natural or surgical menopause. Remifemin was found to have similar benefits to 0.625 mg of conjugated estrogens or 2 mg of diazepam in one study, and to 1 mg of estriol, 1.25 mg conjugated estrogens, or 1 mg of an estrogen-gestagen combination in the other study, However, neither trial was blinded; thus the results cannot be adequately interpreted.
In contrast to the European studies, a recent well-designed U.S. double blind RCT failed to find beneficial effects for Remifemin in women with daily hot flashes who had completed primary treatment for breast cancer. In 85 women (69 completed the study) evaluated at 30 and 60 days, both hot flashes and general menopausal symptoms were reduced equally well by black cohosh and placebo. Changes in blood levels of FSH and LH also did not differ in the two groups.
 
Adverse Effects:
Black cohosh is well-tolerated. In the controlled studies of Remifemin lasting up to 6 months, mild gastric discomfort, weight gain, and headache were reported in a few patients. A single case of unexplained nocturnal seizures in a patient taking black cohosh, chaste tree berry, and evening primrose oil has been reported, but a cause-and-effect relationship with black cohosh is doubtful. Occasional statements in the literature that large doses of black cohosh may cause dizziness, stiffness, and trembling can be traced to old homeopathic provings, and are probably not pertinent to modern use of the herb.
 
Interactions and Side Effects:
There are no known drug interactions.

Cautions:
Based on older studies suggesting estrogen-like properties, some feel that black cohosh is contraindicated for patients with breast cancer or other potential hormone sensitive conditions. Although absolute risks are unknown, recent evaluations have not validated estrogenic activity, and this herb can probably be used in these conditions with relative safety. Black cohosh is not recommended during pregnancy and lactation due to inadequate evaluation. In addition, there are isolated reports of a a premature birth and a malformed infant associated with maternal black cohosh use. A severely poor neurologic outcome in a full-term baby was associated with a combination of black cohosh and blue cohosh taken orally to induce labor, although a cause-and-effect relationship is doubtful.
The German Commission E Monograph recommends limiting the duration of black cohosh use to 6 months; however, this appears to be based on lack of prolonged studies, and not on documented or potentially harmful effects.
 
Preparations & Doses:
There are many preparations of black cohosh available on the market. Remifemin, the standardized German product used in all of the clinical trials, is available in the U. S. as a tablet or liquid extract (distributed by GlaxoSmithKline). Twenty mg of herbal extract is contained in one tablet or 20 drops, standardized to the triterpene glycosides (i.e., 27 -deoxyactein). The dose for menopausal symptoms used in the European clinical trials was 80 mg/day, administered as 40 mg (2 tablets or 40 drops) b.i.d. The manufacturer of Remifemin now states that half this dose, or 20 mg b.i.d., is equivalent to the dose used previously. This change is due to an internal manufacturer's trial in 1996 in which both doses reportedly had equivalent effects; dosing recommendations by the German manufacturer were changed to reflect the lowest effective dose.
Dosing of traditional herbal preparations is roughly 0.5-1 g of dried rhizome or root, taken 3-4 times daily, usually as a decoction, tincture, or extract.

Summary Evaluation

Benefits for menopausal symptoms are suggested by empiric use and some clinical studies; however, clinical effects have not been adequately proven due to lack of high quality clinical trials. One well designed U.S. clinical trial found effects comparable to placebo in breast cancer survivors experiencing hot flashes. Based on recent investigations indicating a lack of direct estrogenic activity, harmful effects are unlikely in patients with breast cancer or other hormone-sensitive conditions. Note that black cohosh has not been shown to have other demonstrated benefits (e.g., prevention of osteoporosis) seen with conventional hormone replacement therapy.