Black cohosh, with the botanical names Actaea racemosa and Cimicifuga racemosa, is an herbal remedy mainly used by women to relieve unpleasant effects of perimenopause and menopause. Black cohosh root is available as a dried extract in capsules and tablets, and as a liquid extract and tincture that can be mixed with water. Although black cohosh is associated with several side effects, it does not appear to interact with many substances.
Black cohosh may be effective for relieving hot flashes, headaches and sleep problems associated with menopause. The North American Menopausal Society recommends using black cohosh along with lifestyle changes for managing hot flashes. Women take black cohosh to relieve menstrual cramps and to regulate the menstrual cycle. Black cohosh is approved in Germany for relieving menopausal symptoms, premenstrual discomfort and painful menstruation.
Black cohosh supplements may have blood-thinning effects, so taking it with drugs that have this effect may increase the risk of abnormal bleeding. Some of these medications include aspirin, ibuprofen, warfarin and clopidogrel. Black cohosh may reduce blood pressure, so it may increase the effects of drugs that lower blood pressure. Because black cohosh might have estrogen-like properties, it may have unpredictable effects with hormonal drugs, such as birth control pills. The American Cancer Society cautions that black cohosh appears to increase the effects of some chemotherapy drugs and decrease the effects of others. Patients taking tamoxifen may experience increased side effects if also using black cohosh root. Rarely, black cohosh use has been linked to serious liver problems, so it may not be safe to take this herb if you use other medications that affect the liver, such as acetaminophen, or drink large amounts of alcohol.
Black cohosh also may interact with many herbs. Blood-thinning properties of black cohosh are attributed to salicylate content, according to InteliHealth. Taking black cohosh along with other herbs containing this chemical, such as aspen bark or willow bark, could increase the risk of bleeding. Numerous other herbs have blood-thinning effects, including Ginkgo biloba and garlic. Garlic and many other herbs can lower blood pressure, which could have an additive effect with black cohosh. Plants with hormone-like effects, including evening primrose and soy, also may interact with black cohosh.
Black cohosh is in the Ranunculaceae plant family, so anyone allergic to other plants in this family, such as buttercup, should not take black cohosh, advises InteliHealth. Because of the salicylate content, people allergic to aspirin or nonsteroidal anti-inflammatory drugs such as ibuprofen or naproxen should not take black cohosh. Pregnant women should not take black cohosh because it may induce premature labor, and the estrogen-like qualities of this herb are contraindicated for women who have, or are at elevated risk for, breast, ovarian or endometrial cancer.
The most common side effects associated with black cohosh are mild, according to InteliHealth, such as upset stomach, nausea, constipation, headaches, dizziness and increased sweating. Some people may experience low blood pressure, slowed heart rate and weight gain. Rare cases have been reported of liver damage and liver failure in people taking black cohosh supplements.