20–40 mg ×2/day of standardized extract.
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Black cohosh, also called Actaea racemosa or Cimicifuga racemosa, is a plant native to North America whose roots and rhizomes have traditionally been used for menstrual and menopausal disorders, first in the traditional medicine of Native American peoples and later in 20th-century German medicine, where the standardized extract was incorporated into the official pharmaceutical formulary as a first-line treatment for the vasomotor symptoms of menopause.
Unlike soy isoflavones or red clover, black cohosh does not act as a phytoestrogen in the classic sense (it does not bind to estrogen receptors with significant affinity in most tissues studied), but rather appears to modulate the hypothalamic serotonergic and dopaminergic systems through its triterpene active constituents, a distinct mechanistic pathway that explains why its safety profile with respect to hormone-sensitive tissues (breast, endometrium) is more favorable than its name suggests.
The indication with the best evidence is relief of the vasomotor symptoms of menopause (hot flashes, night sweats): several meta-analyses have shown significant reductions in the frequency and intensity of hot flashes with doses of 20-40 milligrams daily of standardized extract of the Remifemin brand (CR BNO 1055), one of the few formulations with consistent clinical studies lasting 6-12 weeks.
The effect is modest but clinically relevant: women with moderate to severe hot flashes report reductions of approximately 25-30 percent in the average number of daily hot flashes, with a significant improvement in menopausal quality of life measured by standardized scales (Kupperman, Menopause Rating Scale); the effect is smaller than that of hormone replacement therapy but sufficient for many women who prefer to avoid pharmacological hormones.
Besides hot flashes, several studies show improvements in nighttime sleep, menopause-related anxiety, mood and, in some trials, vaginal dryness with prolonged use; the improvement in sleep is usually associated with the reduction of night sweats, a logical causal relationship that translates into better rest and less daytime fatigue.
In severe premenstrual symptoms, there are preliminary data on the use of black cohosh during the luteal phase of the cycle, although the evidence is much weaker than for menopausal indications and it should not be considered a first-line indication for women with significant PMS.
The most important clinical controversy about black cohosh is its liver safety profile: starting in the 2000s, several isolated cases of acute hepatitis associated with cohosh use were reported, leading European and U.S. regulatory agencies to require label warnings and to recommend caution in people with preexisting liver disease or who take hepatotoxic drugs.
Subsequent systematic studies have concluded that the causal relationship between cohosh and liver damage is probably real but rare (very low incidence, lower than with many other commonly used drugs), and that products lacking quality control or adulterated with other Cimicifuga species may contribute to the problem; using only products with recognized clinical standardization (Remifemin and similar) significantly minimizes this risk.
The effective dose in clinical trials is 20-40 milligrams daily of standardized extract (equivalent to 40 mg of dried root per day), in one or two doses with or without food; clinical effects on hot flashes appear between 4 and 8 weeks, so it is not a fast-acting compound; treatment is typically assessed at 3 months and continued for 6-12 months if the response is satisfactory.
Generally well tolerated at these doses; the most common adverse effects are mild digestive discomfort, headache and, rarely, skin reactions; it is contraindicated in breast cancer or other active hormone-sensitive tumors (out of caution rather than clear evidence of worsening), in pregnancy and breastfeeding, and in people with active liver disease; people taking tamoxifen or anastrozole may use it with medical follow-up because most studies show no interference with their antiestrogenic effect.
Information, not medical advice. Scientific evidence reflects the quality of the studies.