What's new The Food and Drug Administration gave post-menopausal women a new option for treating osteoporosis last week when it approved Menostar, a skin patch that delivers 14 micrograms of estrogen daily -- half the dose of other estrogen drugs. Each patch, to be sold here by Schering AG's American affiliate, Berlex, lasts a week.

Early promise In a two-year trial, Menostar increased bone density in the spine and hip as well as osteoporosis drugs like Evista (raloxifene) and Fosamax (alendronate). "Giving a tiny amount . . . gives these thirsty bone cells the small drink [of estrogren] that they need," said Steven Cummings, a Menostar investigator and estrogen and osteoporosis expert at San Francisco's California Pacific Research Institute. Menostar has not been shown to reduce fractures, though estrogen is known to do so, said Isaac Schiff, chief of obstetrics and gynecology at Massachusetts General Hospital and head of the American College of Obstetricians and Gynecologists' hormone therapy task force.

Benefits The patch offers two advantages over other estrogen drugs: its estrogen used -- plant-based estradiol -- is chemically close to that made by the body, and the skin delivery is more efficient. Pills first go through the liver, which absorbs some estrogen and puts out proteins that can lead to side effects like high blood pressure, said Judith Turgeon, an expert on steroid hormone action at the University of California, Davis.

Down the road Theoretically, estrogen's risks -- breast and uterine cancer and stroke -- should be lower with a lower dose, but long-term safety data aren't in yet, said Schiff. To protect against uterine cancer, Berlex recommends that Menostar users who still have a uterus take progestin for two weeks every six to 12 months. Menostar should be available (by prescription) later this summer and is expected to cost less than Evista or the daily formulation of Fosamax, both of which are now priced at about $70 for 30 tablets.

-- Alicia Ault