Bioidentical hormones are supposedly chemically identical to those made by the human body and are often described as "natural." Many of those available today are custom-mixed – "compounded," in pharmacy parlance - to a woman's specific needs at the direction of her physician. However, "bioidentical" is more of a marketing term than a medical one (the FDA doesn't recognize it), and different medical groups define it differently.
The FDA has warned seven pharmacies that sell these compounded "bioidentical" hormones over the Internet against making misleading claims about safety and efficacy of their products. In letters to the pharmacies sent on Jan. 9, 2008, the FDA said that the compounded products are no safer than conventional forms of hormone replacement therapy. (Premarin and most other FDA-approved hormone therapy contain synthetic hormones.) It also described as "misleading" claims by some pharmacies that their compounded hormones could prevent or treat such diseases as Alzheimer's, stroke, and some cancers, and said that no credible evidence to supports those claims. However, the agency stopped short of prohibiting the pharmacies from filling doctors' prescriptions for these products.
For the record, Wyeth, the manufacturer of Premarin and Prempro, petitioned the FDA in 2005 to restrict the availability of compounded "bio-identical" hormones. According to the Wall Street Journal, sales of Premarin and Prempro have dropped by about half since 2002 when two big government-sponsored studies found that the drugs raised the risks of breast cancer, stroke, and heart attack.
I've never supported universal hormone replacement therapy (HRT) for peri- or post-menopausal women, but some do need reliable short-term relief from intractable symptoms, such as frequent and intense hot flashes, vaginal dryness that makes sex uncomfortable, or overwhelming fatigue and mood changes. HRT is the most effective treatment for these discomforts, but because of the risks involved, it is now recommended only for treatment of severe menopausal symptoms or for women at high risk of osteoporosis who can't take other medications available to preserve bone strength. When HRT is necessary, I have always recommended using bioidentical (in the sense of hormones that are similar or identical in molecular structure to the hormones women make in their bodies) estrogen /progesterone for women who need treatment, specifically Estrace and oral micronized progesterone, both FDA-approved prescription drugs.
Concerns about the "bioidentical" hormones dispensed by compounding pharmacies have been raised by the North American Menopause Society and the American College of Obstetricians and Gynecologists. Both groups have questioned whether the hormones have been adequately tested and maintain that there is no evidence showing that compounded hormones are better or safer than the pharmaceutical drugs. My belief is that they have the same risks as synthetic hormones like Premarin and Prempro, but better side effect profiles. I would like to see them remain available, but I also support the FDA's effort to curtail unfounded claims for their therapeutic benefits.
Andrew Weil, M.D.