Estradiol Safer Than Conjugated Equine Estrogens in Terms of Thrombosis

By Amy Orciari Herman

Conjugated equine estrogens (CEEs) are associated with a higher thrombosis risk than estradiol among postmenopausal women, according to a case-control study in JAMA Internal Medicine.

Using data from a large HMO in Washington state, researchers matched some 180 menopausal women who experienced venous thrombosis, myocardial infarction, or stroke while using oral CEEs or estradiol with 200 menopausal estrogen users without such events. After multivariable adjustment, current CEE use was associated with twice the risk for venous thrombosis relative to estradiol use. MI risk was also higher with CEEs, but this didn't reach statistical significance. There was no association between estrogen formulation and stroke.

Plasma tests among controls revealed that CEE users had increased resistance to activated protein C, "providing biologic support" for the elevated thrombosis risk observed, the researchers note.

Andrew Kaunitz, an OB/GYN with NEJM Journal Watch, points out that CEEs can be 20 times as expensive as estradiol. He says: "For menopausal women choosing to use oral estrogen formulations, estradiol appears a wise choice from a price as well as safety perspective."