A study published on September 30, 2013 in JAMA Internal Medicine found that women who were taking Premarin (conjugated equine estrogen) for menopause had double the risk (odds ratio, 2.08) of developing venous thrombosis (clots in the veins) than woman who took estradiol, both of which are oral estrogen drugs, although there was no difference in the risk for stroke (odds ratio, 1.13) and no statistically significant increase in the risk for heart attack (odds ratio, 1.87).
The researchers studied 384 postmenopausal women between the ages of 30 and 79 who were current users of oral hormone therapy. Among the study participants, there were 68 cases of venous thrombosis, 67 cases of myocardial infarction, and 48 cases of ischemic stroke (along with 201 matched control participants).
With regard to 140 of those in the control group, it was found that users of conjugated equine estrogen had stronger clotting propensity than those using estradiol.
The study concluded that conjugated equine estrogen use “was associated with a higher risk of incident venous thrombosis and possibly myocardial infarction than estradiol use. This risk differential was supported by biologic data. These findings need replication and suggest that various oral estrogen drugs may be associated with different levels of cardiovascular risk.”
The lead researcher of the study stated that the study does not mean that women taking Premarin should stop taking the medication that is intended to help them with their moderate to severe symptoms of menopause, including hot flashes, mood swings, night sweats, and vaginal dryness, because additional research is required to establish if different estrogen drugs have varying levels of cardiovascular risks associated with them.
Pfizer, which manufactures Premarin, had $1.07 billion in sales of Premarin in 2012. Pfizer continues to support women’s use of Premarin for treatment of moderate to severe symptoms associated with menopause.
Pfizer provides the following “Important Safety Information” for Premarin on its website:
Using estrogen-alone may increase your chance of getting cancer of the uterus (womb). Report any unusual vaginal bleeding right away while you are using PREMARIN. Vaginal bleeding after menopause may be a warning sign of cancer of the uterus (womb). Your healthcare provider should check any unusual vaginal bleeding to find out the cause.
Do not use estrogens, with or without progestins, to prevent heart disease, heart attacks, strokes or dementia (decline in brain function). Using estrogens, with or without progestins, may increase your chance of getting dementia, based on a study of women 65 years of age or older.
Using estrogen-alone may increase your chances of getting strokes or blood clots. Using estrogens with progestins may increase your chances of getting heart attacks, strokes, breast cancer, or blood clots.
You and your healthcare provider should talk regularly about whether you still need treatment with PREMARIN.
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