Q. In January, you wrote about an ultra-low dose estrogen patch that helps prevent osteoporosis. Is it available to the public?

A. The estrogen patch we wrote've mentionedabout is available by prescription under the trade name Menostar. Menostar is a clear, dime-sized transdermal patch that delivers 0.014 mg of 17-beta estradiol to the body every day. You change the patch once a week.

Researchers at the University of California at San Francisco studied Menostar in a controlled trial of 417 healthy women ages 60–80. Half wore the patch and half wore a placebo. After two years, bone mineral density at the lumbar spine and hip increased significantly in the women using Menostar, compared with those who wore the placebo patch. Only one woman developed abnormal endometrial cell growth (endometrial hyperplasia), which cleared up after short-term treatment with a progestin. There was no difference in the incidence of breast cancer, blood clots, heart attacks, or strokes in the two groups.

Menostar may offer a new, relatively safe choice for osteoporosis prevention in healthy postmenopausal women who cannot tolerate other osteoporosis drugs, such as bisphosphonates. To protect against endometrial cancer, the manufacturer recommends that women with an intact uterus take a progestin for 14 days once or twice each year.

Nevertheless, be cautious. We don't know whether Menostar improves bone mineral density in postmenopausal women younger than 60. We also lack information about its safety and effectiveness beyond two years (the length of the drug trial). And only longer-term studies will tell us whether treatment with Menostar actually prevents fractures.

— Celeste Robb-Nicholson, M.D.Editor in Chief, HWHW