Less blood clot risk linked to estradiol than to Premarin pills

"Although oral estrogens are effective for managing menopause symptoms, not enough is known about the cardiovascular safety of different oral hormone therapy products relative to each other," said first author Nicholas L. Smith, PhD. He is a professor of epidemiology at the UW School of Public Health, the director of the Veterans Affairs (VA) Seattle Epidemiologic Research and Information Center (ERIC) at the VA Puget Sound Health Care System, and an affiliate investigator at Group Health Research Institute.

To further understand the differences in risk, the researchers also measured clotting (coagulation) factors in the blood of women who did not develop a clot. The researchers found that, compared with estradiol users, conjugated equine estrogen users had levels of blood factors that made them more prone to form blood clots.

The researchers also investigated other cardiovascular events:

• The risk of having a heart attack was somewhat -- but not significantly -- higher in women using oral conjugated equine estrogens than in those using oral estradiol.
• No difference was seen in the risk of stroke.

"If our results are confirmed," Dr. Smith added, "women seeking menopausal treatment and their providers would find this information helpful when selecting a drug." Menopausal symptoms include hot flashes, night sweats, and vaginal dryness, burning, and irritation.

This project, part of the Heart and Vascular Health study, involved 384 Group Health members, aged 30-79, who were taking oral estrogen for menopause symptoms from 2003 through 2009. On February 1, 2005, Group Health's formulary switched its preferred oral estrogen from conjugated equine estrogens to estradiol. The Heart and Vascular Health study is a case-control study, where Group Health members who develop cardiovascular events are matched with control members who do not.