A new alternative to estrogen may offer older women many of the hormone's heart- and bone-protecting advantages without one of its most worrisome side effects - an increased risk of breast cancer.

However, experts warned it is too soon to say whether the drug, raloxifene, is a "magic bullet," with estrogen's strengths and not its drawbacks.Millions of women take estrogen to counter the effects of menopause, including thinning bones. But many refuse to take it because of its potential to increase the risk of breast cancer, and scientists have been searching for a sub-sti-tute.

Raloxifene already is approved by the Food and Drug Administration to prevent osteoporosis in postmenopausal women, and research indicates it reduces the risk of breast cancer as well.

Now a study has found that raloxifene, like estrogen, might also protect the heart, researchers reported in Wednesday's Journal of the American Medical Association.

"It potentially has promise to be a pathway to go beyond the estrogen dilemma," said the lead author, Dr. Brian W. Walsh, director of the Menopause Center at Harvard-affiliated Brigham and Women's Hospital in Boston.

The study found raloxifene lowered levels of "bad" cholesterol, or LDL cholesterol, by 12 percent in postmenopausal wom, compared with 14 percent for estrogen. Raloxifene failed to improve the women's levels of "good" cholesterol, or HDL, an important protector against heart disease. The drug also had much less of a favorable effect than estrogen does on a blood fat called lipoprotein-a.

The drug did, however, lower levels of a clotting protein called fibrinogen, another risk factor for heart disease, while estrogen did not.

The study involved 390 healthy, postmenopausal women at eight medical centers nationwide. Some were given standard hormone replacement therapy that included estrogen; some were given dummy pills; and some received raloxifene. The maker of raloxifene, Eli Lilly & Co., helped pay for the study.

Walsh said it is too soon to tell if raloxifene, marketed as Evista, will become an alternative to estrogen, the most commonly prescribed drug in America.