WASHINGTON -- Postmenopausal women can take a pill containing half the usual dose of estrogen to protect against crippling osteoporosis with fewer side effects, the Food and Drug Administration decided Wednesday.
The FDA approved Estratab's 0.3 milligram of estrogen as adequate protection against thinning bones.
"This provides a choice for people," said FDA drug evaluation chief Dr. Janet Woodcock.
Osteoporosis afflicts an estimated 10 million Americans, mostly elderly women. Standard treatment is 0.625 milligram of estrogen, which also fights menopausal symptoms and helps keep women's hearts healthy.
But only 20 percent of postmenopausal women considered estrogen candidates actually take it, because long-term use may increase breast cancer and it causes other side effects.
The non-hormonal drugs Fosamax and Evista also can fight osteoporosis, but how they compare to estrogen is debated.
Estratab manufacturer Solvay Pharmaceutical funded a two-year study of different estrogen doses in 406 women. The 0.3 milligram Estratab -- already sold to fight menopausal symptoms -- proved enough to preserve existing bone mass and to help some women slightly increase it.
Estratab caused less breast tenderness, headaches and nausea than higher estrogen doses.
In addition, high-dose estrogen can cause a uterine cancer, so patients are prescribed the hormone progestin to offset that side effect. Low-dose Estratab didn't appear to affect the uterus.
But because more estrogen builds even more bone, some women not concerned with the side effects may still choose the higher dose, Woodcock said.