Premarin (generic name: conjugated estrogen tablets, USP) was the first estrogen-only hormone replacement therapy (HRT) drug marketed to treat the symptoms of menopause. It is typically prescribed for women without a uterus. Initially marketed in 1942, Premarin is today the most popular HRT drug, and one of the most prescribed drugs in the world.

Premarin has been linked to the following serious side effects: ovarian cancer, lupus, scleroderma, gallbladder cancer, and stroke. The National Institutes of Health recently stopped a trial of women taking Premarin after finding the pills not only failed to reduce the risk of heart disease but raised the possibility of a stroke.

The Premarin trial was the second large trial of HRT to have been halted in two years. In July 2002, women taking Prempro (conjugated estrogens/medroxyprogesterone acetate tablets; includes Premarin) were told to stop because of the risk of heart attack, stroke, and some forms of cancer.

In a report published in the Journal of American Medical Association , doctors report that women who take estrogen-only HRT such as Premarin for a long period of time have a higher-than-average risk of developing ovarian cancer. The researchers noted a 7% increase in risk associated with every extra year of estrogen HRT use.

Those who took estrogen for at least 10 years were twice as likely to develop ovarian cancer and those who used the drugs for 20 or more years were three times as likely to develop ovarian cancer as those who did not take the hormone, the report indicates.

There are approximately 11 million women currently taking Premarin. The popularity of this drug is due both to its extensive history and an aggressive marketing campaign by Wyeth Pharmaceuticals Inc.