Black Cohosh

Actaea racemosa L. is a perennial of Ranunculaceae, the buttercup family. It was long known as Cimicifuga racemosa (L.) Nutt., and the US Pharmacopeia’s 2008 safety review describes Actaea racemosa as the current name and Cimicifuga racemosa as the former one. The European Pharmacopoeia defines the drug as the rhizome and root of Actaea racemosa L. (syn. Cimicifuga racemosa), but EU regulatory documents and many European studies still use the Cimicifuga name, often shortened to CR. NCCIH lists black snakeroot, macrotys, bugbane, bugwort, rattleroot, and rattleweed as other common names. NCBI Taxonomy files it as taxon 64040. EMA notes that it is native to the eastern United States and Canada, the source of essentially all commercial stocks. It grows in shady hardwood forest, forming a mound of large compound leaves with toothed leaflets, and in summer sends up tall, slender wands of small white flowers whose fluffy look comes from their many stamens.

The medicinal part is the rhizome and root (NCCIH). The European Pharmacopoeia standard requires at least 1.0% triterpene glycosides in the dried drug, expressed as monoammonium glycyrrhizate (EMA). ODS describes supplements as powdered whole herb, liquid extracts, and dried extracts in pill form, varying considerably in composition. The EU monograph covers only three extracts: dry extracts made with 58% or 60% ethanol, and one made with 40% isopropanol (propan-2-ol), the solvent used for Remifemin, a brand tested in several trials. Doses of these extracts are a few milligrams: in products described by EMA, 2.5–2.8 mg of dry extract corresponds to about 20 mg of root. US supplements often state milligrams of a different extract altogether; the HALT trial used 160 mg a day of a 70% ethanol extract. Milligram figures on different labels are not comparable.

The chemistry is complex and the active principle unknown. ODS lists triterpene glycosides such as actein, 23-epi-26-deoxyactein, and cimicifugoside, resins such as cimicifugin, and aromatic acids including caffeic, isoferulic, and fukinolic acids. EMA states that neither the mode of action nor the constituents responsible for any improvement in menopausal complaints are known, and that no constituent with known therapeutic activity or active marker can be recognized. Identity is a real problem: NCCIH reports that some commercial products have contained the wrong herb, or mixtures with other herbs not on the label, and ODS notes that impurities, adulterants, or the wrong Actaea species may explain some liver cases, though this has not been confirmed. Blue cohosh (Caulophyllum thalictroides) is an unrelated plant with different and more serious risks (NCCIH).

Black cohosh is an Indigenous North American medicine. EMA’s assessment report notes that the roots and rhizomes were used since pre-Columbian times for malaise, kidney disorders, rheumatism, snakebites, and nervous and gynaecological disorders, especially as a uterine stimulant and to aid labour. NCCIH adds malaria, sore throat, and menstrual cramps; ODS adds musculoskeletal pain, fever, cough, pneumonia, and menstrual irregularities, and says European settlers adopted it as a tonic for women’s reproductive health. The plant entered the United States Pharmacopeia in 1830 under the name black snakeroot (EMA). ODS lists snakeroot, black bugbane, rattleweed, macrotys, and rheumatism weed as other, mostly historical, names, a record of how widely and for how many purposes it was once used.

Germany turned it into a menopause medicine. NCCIH says black cohosh has been used medicinally there since the late nineteenth century, and EMA records its use since 1940 for premenstrual, menstrual, and menopausal complaints. Germany’s Commission E published a monograph on 2 March 1989 covering all three uses, then revised it on 14 December 1994 to keep only menopausal symptoms such as hot flashes, because the other uses were not sufficiently documented; the revised monograph gave a daily dose equivalent to 40 mg of herbal substance for up to six months. An Austrian product has been sold for menopausal symptoms since 1973, and the UK has a traditional product for rheumatic pain. ODS notes that studies of various designs have tested black cohosh for menopausal symptoms since the 1950s.

Modern trials and safety signals arrived together. The HALT trial ran from 2001 to 2004 in Washington State and published its negative result in 2006. Reports of liver injury led Australia to require a liver warning on black cohosh products from 2007, and the US Pharmacopeia to recommend a cautionary label in 2008; the US FDA does not require one (ODS). The EU’s herbal committee adopted its first monograph on 25 November 2010 and a revision on 27 March 2018. Because of the possible liver risk, black cohosh was placed under EU-wide periodic safety review; that review concluded the benefit–risk balance was unchanged but that hepatotoxicity should continue to be closely monitored, and in November 2025 the committee decided no revision of the monograph was needed.

Black cohosh was long assumed to be a plant oestrogen, because it eases symptoms that oestrogen treats. That idea has not held up. EMA’s assessment concludes that although early laboratory studies suggested binding to oestrogen receptors, recent data do not support it, and that available non-clinical and clinical data suggest black cohosh does not have an oestrogenic effect mediated through the oestrogen receptor. Where measured, it did not change circulating oestradiol, FSH, or LH, or show oestrogenic effects on breast, endometrial, or vaginal tissue (EMA). MSKCC likewise notes no effect on LH, FSH, prolactin, or oestradiol in studies, and anti-proliferative effects in oestrogen-receptor-negative cells, suggesting that any effects run through other pathways.

Current hypotheses focus on the brain. MSKCC summarizes dopaminergic, noradrenergic, serotonergic, and GABA-related effects in laboratory studies. EMA describes extracts that bind and activate serotonin 5-HT1A and 5-HT7 receptors in cell systems, the identification of Nω-methylserotonin as one active fraction, and dopamine D2-like effects on pituitary cells and on body temperature in mice. EMA cautions that none of these findings explains the clinical effect or translates into practice, and that it is not known whether the relevant compounds cross the blood–brain barrier. Laboratory doses often bear no relation to human doses.

The liver injury mechanism is unknown. Some cases have resembled autoimmune hepatitis on biopsy and responded to steroids (MSKCC), which points to an idiosyncratic, immune-type reaction rather than predictable toxicity. EMA notes that rats given more than 1,000 mg of ethanolic extract per kilogram developed fatty change in the liver, a dose it calculates as about 200 mg/kg in humans against a therapeutic dose of about 0.08 mg/kg, so animal data do not explain human cases. On drug metabolism, extracts inhibited CYP1A2, CYP2C9, CYP2D6, and CYP3A4 in test tubes, and black cohosh weakly inhibits CYP2D6, but clinical studies in healthy volunteers found no clinically relevant effect on CYP enzymes or P-glycoprotein (EMA).

Menopausal symptoms, the case for: Osmers and colleagues (Obstetrics and Gynecology 2005) randomized 304 women with climacteric complaints to the isopropanolic extract, equivalent to 40 mg of root daily, or placebo for 12 weeks. The extract was more effective than placebo on the Menopause Rating Scale, with the hot flash subscore the most responsive measure and greater benefit in women early in the menopausal transition. EMA’s committee accepted three extracts as well-established medicines on the basis of randomized and observational studies, while acknowledging that no single good-quality controlled trial covers all the symptoms on the validated rating scales. Sadahiro and colleagues (Menopause 2023) pooled 22 trials with 2,310 women, including products combining black cohosh with other ingredients, and found improvements over placebo in overall menopausal symptoms, hot flashes, and somatic symptoms, but not in anxiety or depression.

The case against: Leach and Moore (Cochrane 2012) reviewed 16 randomized trials with 2,027 women using a median of 40 mg a day for an average of 23 weeks. Black cohosh did not differ from placebo in daily hot flash frequency (three trials, 393 women) or menopausal symptom scores (four trials, 357 women), hormone therapy did better, and trial quality was generally unclear; the authors found insufficient evidence to support its use. In the HALT trial, Newton and colleagues (Annals of Internal Medicine 2006) randomized 351 women aged 45 to 55 to 160 mg a day of black cohosh, two multi-herb regimens, hormone therapy, or placebo for a year. The herbal groups never differed from placebo by as much as one symptom a day; hormone therapy reduced symptoms by about four a day. ODS describes a second 12-month trial, using 128 mg a day, that also found no difference from placebo.

Guidelines side with caution. The North American Menopause Society’s 2023 position statement does not recommend supplements or herbal remedies for hot flashes, and recommends cognitive behavioural therapy, clinical hypnosis, SSRIs or SNRIs, gabapentin, and fezolinetant as evidence-based non-hormone options, with hormone therapy still the most effective treatment. ODS notes that the American College of Obstetricians and Gynecologists also concluded the data do not show herbal supplements such as black cohosh to be effective. One plausible reason for the conflicting results is that trials tested different products: the positive Osmers trial used the European isopropanolic extract, while HALT and the trial ODS describes used different ethanolic extracts, labelled at 128–160 mg a day. That is a hypothesis, not a demonstrated explanation.

Hot flashes after breast cancer: Pockaj and colleagues (Journal of Clinical Oncology 2006), in a cancer cooperative group trial prompted by hot flashes in women during or after breast cancer treatment, randomized 132 patients to a crossover of black cohosh 20 mg twice daily and placebo; hot flash scores fell 20% on black cohosh and 27% on placebo, a non-significant difference, and slightly more patients preferred the placebo period. Fritz and colleagues (Integrative Cancer Therapies 2014) reviewed 26 studies in women with or at risk of breast cancer and found a lack of evidence that black cohosh reduces hot flashes in this group. NCCIH calls the question uncertain. A 2019 trial in 85 women with breast cancer receiving hormone-suppressing injections reported lower menopause scores with the isopropanolic extract, but EMA judged that no firm conclusions could be drawn from it.

Other uses lack support. Commission E dropped premenstrual and menstrual indications in 1994 because they were not sufficiently documented, and NCCIH says there are not enough reliable data for other uses. MSKCC notes studies in which black cohosh did not improve bone density or 10-year coronary risk in early postmenopausal women, and EMA regards animal data on bone protection as preliminary. Black cohosh is sometimes promoted to induce labour; that is unsafe, and MSKCC reports severe hyponatraemia in a woman who took repeated doses during prolonged labour.

EU well-established use (EMA/HMPC/48745/2017, adopted 27 March 2018), for adult women with menopausal complaints such as hot flashes and profuse sweating, in solid oral dosage forms: dry extract with 58% ethanol (DER 5–10:1), 2.8 mg twice daily (5.6 mg per day); dry extract with 60% ethanol (DER 4.5–8.5:1), 6.5 mg once daily; or dry extract with 40% isopropanol (DER 6–11:1), 2.5 mg or 5.0 mg once or twice daily, 5.0 mg per day. EMA’s product data show these amounts correspond to roughly 40 mg of root and rhizome a day. There is no relevant indication for men, children, or adolescents. If symptoms persist, consult a doctor or pharmacist, and do not take black cohosh for more than six months without medical advice.

US supplements are less standardized. ODS reports that products are frequently standardized to at least 1 mg of triterpene glycosides per daily dose, while Remifemin is standardized to the equivalent of 40 mg of root and rhizome per daily dose of two tablets, not to triterpene content, and has been reformulated over time. Trials in the Cochrane review used 8–160 mg of various extracts daily, with a median of 40 mg (ODS). The US Pharmacopeia recommends a label warning to stop and consult a practitioner with a liver disorder or symptoms of liver trouble, but the FDA does not require it. Australia has required a liver warning on black cohosh products since 2007.

Quality is a safety issue here. EMA’s assessors noted that case reports of liver injury rarely identify the product involved, and that the reports show the need for regulated products with guaranteed quality and adequate labelling. Choose a product that names Actaea or Cimicifuga racemosa, the root and rhizome, and the extract, preferably a licensed herbal medicine where available. Multi-herb menopause blends add unknown risks without proven benefit; in HALT, a multibotanical regimen plus soy produced worse symptom intensity than placebo at 12 months. Do not confuse black cohosh with blue cohosh, and never use either to start labour.