Black Cohosh Safety
- Evidence shows herb considered safe for use in perimenopausal women
- Liver damage as a result of black cohosh use is extremely rare
- All black cohosh products must contain a warning identifying the potential risk of liver damage
- If you experience any signs or symptoms of liver damage, cease use of black cohosh immediately
- Patients should ensure that all of their health professionals are aware of any herbal medicines they are taking
There have been some questions raised about the safety of black cohosh, specifically with regards to liver damage and breast cancer. Overall, an examination of the evidence in the research journals, detailed below, will show that this herb is considered to be safe to use for perimenopausal symptoms.
General evidence of safety of black cohosh use
In 2003, the Journal of the North American Menopause Society, Menopause, published two papers reviewing the safety of black cohosh. The first paper (a literature review) looked at black cohosh use in over 2,800 patients and concluded that black cohosh appears to be a safe option for women for the management of perimenopausal symptoms.
The second paper concluded that the side effects from black cohosh are rare, mild and reversible. The most common side effects reported were digestive upsets and rashes. There were a few more serious side effects listed including thrombosis (blood clots), high blood pressure and slow heart rate. It concluded that the cause for these specific side effects could not be determined.
Black cohosh and liver damage
In October 2002, in the Medical Journal of Australia, there was a single case report of a 47 year old Australian woman who developed acute hepatitis (inflammation of the liver) and as a result, needed a liver transplant. It was reported that this woman had been taking a black cohosh preparation for one week. The herbal product that was used was not analysed to show that the product did actually contain the herb black cohosh (which has been the case for the majority of reports of black cohosh and suggested liver damage) and therefore cannot conclude the herb as the cause of the liver damage. The type of hepatitis that was observed in this woman was a severe immune reaction typical of a particular individual immune reaction and not because of a direct toxic injury.
After this first report, other authors started to suggest black cohosh as the cause of liver damage when a liver reaction was seen in a person who was taking the herb.
By 2006, there had been around 40 cases of suspected liver reactions due to black cohosh worldwide, nine of which occurred in Australia. Of the Australian cases, four were hospitalised, with two requiring liver transplants.
This prompted the Australian Therapeutic Goods Administration (TGA) to issue a warning of the potential liver reaction from black cohosh, as they believed there was ‘sufficient evidence of a causal association between black cohosh and serious hepatitis’. As a result of this, future labels of products containing black cohosh will read: ‘Warning: black cohosh may harm the liver in some individuals. Use under the supervision of a healthcare professional’.
The TGA more recently established an expert advisory group to review the existing regulatory controls on black cohosh. The expert group concluded that there appears to be an association between the use of black cohosh and liver damage, but it is very rare. They state that it was not possible to tell, with any certainty, the strength of the association, or any particular vulnerable group, type of preparation, dose, duration of use or specific products.
The expert group also determined that black cohosh is still suitable for use in complementary medicines, but recommended that the current warning statement on the medicine label be revised to better inform consumers about the risk and also to provide sufficient information to assist in the early detection of liver damage and, if detected, to seek medical attention.
The European Medicines Agency Committee on Herbal Medicinal Products (HMPC) also reviewed the evidence on black cohosh in a recent 2006 analysis (revised version January 2007).
The HMPC analysed all the reports of liver reactions due to black cohosh. Eight international experts formed the group dealing with hepatotoxicity (liver toxicity).
The report examined 15 clinical studies (between 1983 and 2005) and overall no case of significant liver dysfunction was reported. It was noted that long-term safety of black cohosh was not studied.
While the report overall demonstrated that there were only two cases where black cohosh was possibly related to liver damage the HMPC wanted to draw the attention of the public to the potential serious liver reaction that may occur in patients using products containing black cohosh. They offer the following advice:
- Patients should stop taking black cohosh and consult their doctor immediately if they develop signs and symptoms of liver injury. Symptoms of liver disease can include:
- Jaundice (yellowing of the skin or whites of the eyes)
- Dark urine
- Weight loss
- Unusual tiredness
- Appetite loss
- Bloated abdomen or abdominal pain.
- Patients using herbal medicinal products should tell their doctor about it.
Healthcare professionals are encouraged to ask patients about use of products containing black cohosh.
Suspected hepatic reactions should be reported to the national adverse reaction reporting schemes.
Several key factors need to be considered when looking at the evidence suggesting black cohosh as a cause of liver damage
- In many of the cases, the presence of black cohosh has not been definitely established (i.e. the product was not tested to show that it actually contained the herb black cohosh).
- In most cases the name and dosage of products has not been specified.
- In some reports, the products used contained multiple ingredients; the patient was taking more than one medication, or was suffering from other medical conditions.
- There are at least 20 common names for black cohosh making the likelihood of mistaken substitution of this herb for another herb a possibility.
- No information regarding plant part used, extraction medium, the amount of the herb taken or method of extraction has been listed in the reports.
- Hepatitis, for which no cause can be identified, is not uncommon and cannot be excluded.
- Overall there is a very low incidence of reported suspected liver damage considering the widespread use of black cohosh.
- There is a potential for misinformation when an author who is not herbally qualified attempts to explain a possible reaction.
- There is an ongoing study of black cohosh and menopause at the Columbia University, New York City, which is investigating liver function tests in subjects every 2-3 months.
In summary, while acute liver failure has been suspected with black cohosh, it is extremely rare and somewhat unpredictable.
Black cohosh and breast cancer
Of all the herbal medicines that a breast cancer survivor may consider using, black cohosh has the most research supporting its use and has the greatest amount of safety data.
There have been two clinical trials on black cohosh and breast cancer patients to date. In an open-label randomised clinical trial over 12 months, black cohosh reduced the number and severity of hot flushes in premenopausal (age 35-52) breast cancer survivors on Tamoxifen treatment. In a second study of only two months duration, black cohosh was no better than placebo (dummy treatment) for reducing number and intensity of hot flushes, in women with a history of breast cancer. More than two thirds of the women were on Tamoxifen in this study and possibly the shortness of the study limited the results.
A recent review of the research looking at black cohosh and its safety and effectiveness in cancer has supported the information above. While the effectiveness of the herb for treatment of symptoms is inconclusive, the report states that black cohosh has a relatively good safety profile, does not show phytoestrogen activity and the concerns about liver damage are inconclusive. The paper also states that there are no studies suggesting that black cohosh has a protective role in cancer prevention.
The most important factor is to get the approval of the oncologist and breast specialist before commencing treatment with black cohosh. Of all the herbal medicines that a breast cancer survivor may consider using, black cohosh has the most research supporting its use and has the greatest amount of safety data. Longer trials of five years or more are needed to establish breast cancer safety data more conclusively. Black cohosh is only indicated for hot flushes, vaginal dryness and aches and pains and should only be taken for as long as symptoms persist.
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