Pfizer’s Premarin for Menopause Linked to Blood Clot Risk

Pfizer’s Inc.’s Premarin for menopause may be tied to a higher risk of blood clots than another common estrogen treatment called estradiol, a study found.

Women taking Premarin, also known as conjugated equine estrogens, had double the risk of a blood clot in the veins than women taking estradiol, a synthetic form of estrogen, according to research today in JAMA Internal Medicine. No difference between the treatments was seen in the risk of stroke.

Today’s findings don’t mean women should stop taking Premarin, an estrogen gathered from the urine of pregnant horses, to ease their menopausal symptoms such as hot flashes, night sweats, mood swings and vaginal dryness, said Nicholas Smith, the lead study author. More research is needed to replicate the results so doctors can say for sure that different types of estrogen drugs carry varied levels of heart risks, he said.

“The assumption has held that all oral estrogens have similar safety profiles. This may not be the case,” Smith, a professor of epidemiology at the University of Washington School of Public Health in Seattle, said in an e-mail. “More comparative safety studies of commonly used treatments are needed.”

Researchers in the study included 384 post-menopausal women ages 30 to 79 who were taking hormone treatments and were part of the heart and vascular health study with Group Health Cooperative, a health-care system in Washington state.

Study Findings

From January 2003 to December 2009, 68 women developed blood clots, including 39 who used Premarin, 67 had a heart attack, including 38 who used Premarin, and 48 had a stroke, including 25 who used Premarin. Those women were matched with 201 patients who didn’t have any heart events and were current estrogen users.

While the research showed the risk of having a heart attack for Premarin users was higher than those taking estradiol, the findings weren’t statistically significant.

Pfizer “strongly believes” in the use of conjugated estrogens as a treatment option for women who have moderate to severe menopausal symptoms, Jennifer Kokell, a company spokeswoman, said in a statement. Premarin generated $1.07 billion in sales last year.

“Conjugated estrogens have been used for over 70 years as an effective treatment option for women experiencing menopausal symptoms,” Kokell said. “Pfizer remains committed to helping meet the needs of women going through menopause.”

Women should use hormones at the lowest dose for the shortest amount of time, according to U.S. recommendations.

Health Risks

More than 6 million women took New York-based Pfizer’s Premarin and Prempro, a combination of estrogen and progestin, to treat their menopausal symptoms before they were linked in 2002 to health concerns such as breast cancer.

The Women’s Health Initiative, a U.S.-sponsored study of disease and disability in postmenopausal women, was halted in 2002 after finding that women who took Pfizer’s Prempro had a higher breast-cancer risk. That led to a decline in sales of hormone replacement therapy pills. The Women’s Health Initiative Estrogen-Alone Trial was stopped in 2004, a year earlier than planned, because of an increased risk of stroke.

The Food and Drug Administration says that women shouldn’t use hormone therapy to prevent heart attacks and strokes or memory loss and Alzheimer’s disease. Studies also haven’t shown the treatments prevent aging and wrinkles or increase sex drive, the agency said.

Hormone treatments may help relieve menopausal symptoms and reduce a woman’s chance of getting osteoporosis, according to the FDA. Still the drugs may raise the chance a woman gets blood clots, heart attacks, strokes, breast cancer and gall bladder disease. Women who have a uterus and take estrogen may have a higher risk of cancer of the uterine lining, the FDA said.

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