A widely publicized study that has already linked hormone replacement therapy to an increased risk of stroke, heart attack and some cancers also uncovered a blood clot hazard, researchers reported on Tuesday.

The study, called the Women’s Health Initiative, found that women taking estrogen plus progestin at the strength once commonly in use had a doubled risk of venous blood clots, which can travel to the lungs and cause death.

The estrogen-progestin combination is most often sold in the United States as Wyeth’s Prempro. The U.S. Food and Drug Administration now recommends that women seeking relief from menopausal symptoms should use such drugs at the lowest effective dose and for the shortest time necessary.

Wyeth in the years since 2002 when the study results began to emerge has introduced two lower strength versions of Prempro.

The blood clot data, reported by researchers at the University of Vermont in Colchester, came from the study that involved 16,608 postmenopausal women between the ages of 50 and 79 recruited from 1993 through 1998. Some women received the hormone drug while others got an inert placebo.

The study found that the blood clot risk was highest for those who were overweight, and that a genetic disposition for clots as well as advancing age also increased the risk. Taking aspirin to thin the blood did not counteract the problem, it said.

“The implications of these findings may be important for the use of postmenopausal hormone therapy in the treatment of menopausal symptoms among younger postmenopausal women,” the researchers concluded.

The American College of Obstetricians and Gynecologists said recently that more research is needed into whether hormone replacement therapy may be safer for younger women.

SOURCE: Journal of the American Medical Association, October 6, 2004.