Black cohosh (Actaea racemosa)

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15. Safety

15.1 Adverse effects in trials

Across more than 6300 trial participants the HMPC found adverse events mostly mild: gastrointestinal upset, rash and other allergic skin reactions, facial or peripheral oedema; frequency not known [5,6]. Mills and Bone add headache, vertigo, weight gain, breast tenderness, heavy legs and vaginal bleeding as minor reports, and note that higher doses have been linked with headache [2]. A 2022 review of spontaneous reports, case reports and trials found no evidence that black cohosh causes weight gain [49]. Liver enzymes were unchanged in the trials that measured them (Osmers, Frei-Kleiner, Nappi, Bai [6]; Geller [44]), and a meta-analysis of five RCTs (1117 women) of the isopropanolic extract found no adverse effect on liver function (Naser 2011, as reported by Mills and Bone [2]).

15.2 Liver injury

Case record. A Queensland series of six patients with severe hepatitis after herbal remedies (Princess Alexandra Hospital, Brisbane, 1996-2001) included one woman who needed urgent liver transplantation for fulminant hepatic failure after brief use of black cohosh; the products were not analysed [50]. Mills and Bone identify her as a 47-year-old who had taken black cohosh alone for about a week, and note that the dose and product were not stated and rechallenge was not done [2]. They also record a second Australian case: a 52-year-old woman with acute liver failure, treated by liver transplantation, who had taken a pharmacist-prescribed mixture of 1:1 liquid extracts containing 10% black cohosh at 7.5 mL twice daily (about 1.5 mL of 1:1 black cohosh, or 1.5 g of herb, a day); TGA analysis was said to confirm golden seal, black cohosh and Ginkgo in the mixture [2]. That dose lies inside the practitioner range in section 12. In a US case, a 54-year-old woman who had taken black cohosh 1000 mg daily for 8 months (and drank two glasses of wine nightly) developed fulminant hepatic failure and died in the operating theatre during liver transplantation; the authors scored the case RUCAM 6 (probable) [51]. The HMPC’s 2007 review found 4 of 44 poorly documented cases coherent with black cohosh (2 probable, with autoimmune hepatitis), then five cases assessed as "probable" by RUCAM by 2010, three further literature cases in 2013-2014, and a 2017 German report of toxic hepatitis (RUCAM 7) on one of the extracts the HMPC accepts (DER 4.5-8.5:1, ethanol 60%); one death with liver failure had several other possible causes (fluoxetine, paracetamol, propoxyphene, alcohol) [6]. Teschke’s group analysed all 69 cases reported by 2009 and found no likelihood of causality in 68, most being confounded or missing critical information (as reported by Mills and Bone [2]).

Wrong species. Health Canada analysed three products linked to liver reports and found no authentic black cohosh; several licensed products without authentic black cohosh were then withdrawn [2]. The TGA Laboratories found other species in 35% of Australian products tested in 2001 [2]. The HMPC adds that the product used is rarely identified in the published case reports [6].

Australian regulatory action. In February 2006 the TGA reported 47 liver cases worldwide, 9 Australian (4 hospitalised, 2 needing transplantation), judged the evidence of a causal association sufficient, and required a label warning [2,25]. The current Permissible Ingredients Determination requires oral medicines containing A. racemosa to carry warning statement BCOHOSH: that in very rare cases black cohosh has been associated with liver failure, listing yellowing of skin or eyes, dark urine, nausea, vomiting, unusual tiredness, weakness, abdominal pain and loss of appetite as reasons to stop the product at once [8]. MediHerb carries equivalent wording and contraindicates use in pre-existing liver disease [15].

TGA safety communications and DAEN (checked in September 2026 by Medicine). The TGA’s February 2006 statement is quoted here from Mills and Bone [2]; the TGA-hosted Australian Adverse Drug Reactions Bulletin file for that period returned HTTP 404 and the TGA site search returned no current black cohosh safety page to our tools, so no safety communication later than 2006 is cited. The Database of Adverse Event Notifications (DAEN, medicines) sits behind an interactive terms-and-conditions page that our tools cannot query; Australian report counts for Actaea or Cimicifuga were therefore not obtained and must be pulled by hand before release. The operative Australian requirement is the BCOHOSH warning in the current Permissible Ingredients Determination [8].

Assessment (AIP comment). Causality is unproven in most cases but a rare idiosyncratic reaction cannot be excluded, and substitution may explain some cases. The practical rule is the same either way: authenticate the raw material (section 10), avoid in liver disease, and stop at the first sign of liver injury.

15.3 Contraindications and precautions (each with source and grade)

15.4 Herb-drug interactions

15.5 Pregnancy and lactation

Mills and Bone assign Australian category B2 and record the traditional restriction except to assist childbirth; in a 1999 survey 45% of 90 US nurse-midwives who used herbs used black cohosh to stimulate labour, and a neonate suffered hypoxic-ischaemic brain damage after the mother took blue and black cohosh at about 42 weeks [2]. Animal data on reproductive and developmental toxicity are insufficient, and there are no data on the dry extracts in pregnancy or lactation [6]. Mills and colleagues give labour induction "evidence grade E" and the pregnancy use "evidence level 4" on their own scales [54]. AIP position: avoid in pregnancy and lactation.

15.6 Breast cancer

In MMTV-neu transgenic mice fed black cohosh for 12 months, primary mammary tumour incidence was not increased but lung metastases were significantly more frequent (Davis 2008, as reported by the HMPC and Mills and Bone [2,6]); Mills and Bone question the relevance of the model [2]. In women, a German cohort of 18 861 breast cancer patients, 1102 of them treated with the isopropanolic extract, found no increase in recurrence (Henneicke-von Zepelin 2007 [2,6]); a US case-control study (Rebbeck 2007 [2,6]) and a German case-control study [55] found reduced risk, and the VITAL cohort found no association (HR 1.17, 95% CI 0.75-1.82) [56]. The HMPC calls the German case-control design confusing, with many confounders [6]. A systematic review found no association with increased breast cancer risk [41]. The observational designs are prone to confounding, so absence of harm is not established; the HMPC advises against use after hormone-dependent tumours without specialist oversight [5].

15.7 Children and older people

No data in children. Trials enrolled women up to about 70 years; no specific studies in older people [6].

15.8 Toxicology and overdose

Six-month rat study of the isopropanolic extract (Korn 1991): NOEL 22.5 mg/kg (human equivalent about 3.6 mg/kg, against a daily dose of about 0.08 mg/kg for a 60 kg adult) [6]. Mills and Bone summarise the same study as showing no toxic effects at up to 5 g/kg/day [2]; the two sources disagree and QA should check the study report. The Ames test on the isopropanolic extract does not meet current guidelines; a guideline-conform Ames test exists for the 60% ethanolic extract [6]. A US National Toxicology Program study of an ethanolic extract (90 days, up to 1000 mg/kg/day) found dose-dependent haematological changes and more micronucleated red cells in rats and mice [46]. Early reports describe nausea, vomiting, severe headache, vertigo, joint pain, red eyes and weak pulse after 5 g of herb or 12 g of fluid extract, perhaps partly due to baneberry admixture [2,24]. No case of overdose has been reported in the databases the HMPC searched [6].

15.9 Referral

Anyone with liver disease, a hormone-dependent cancer, pregnancy or breastfeeding, or taking statins or cancer treatment, should consult a degree-qualified herbalist with competencies and adequate training in pharmacognosy before using black cohosh.