What is Premarin®?

Premarin® stands for Pregnant Mares' Urine (PREgnant MARes' urINe); PMU for short.

Premarin (including Prempro, Premphase, Prempac, and Premelle) is a drug made up of conjugated estrogens obtained from the urine of pregnant mares -- put out in many forms (pills, creams, injections, patches, vaginal rings) and is used to reduce the symptoms of menopause in women intact or women who have had a hysterectomy. It is also prescribed to try to diminish the risk of osteoporosis and reduce the chance of heart disease in women over 50.

As of November 2003, approximately nine million American women were still taking some form of Premarin as in PremPro before the negative Women's Health Initiative study results became known. There was a reduction of 25% from the high figure of approximately 12 million women taking PMU based medications in 1999. About a third of the approximately fifty-five million post menopausal women in the United States are on synthetic estrogen replacement therapy (ERT), or hormone replacement therapy (HRT), and of them, about 49% currently use “PMU” based products (down from a high of 79% in 1999) -- while there are a number of estrogens excreted by the pregnant mare, estrone sulfate, equilin, and equilenin are the most significant.

It is the only human estrogen replacement drug that is derived from an animal (hormones beginning with the letter "e" are specific to equines).

The company that distributes and markets it world-wide, Ayerst Organics Ltd. (the world's only producer of PMU) is a subsidiary of Wyeth Inc .  Wyeth Laboratories, Inc. traces its roots to Philadelphia, Pennsylvania, U.S.A., where, in 1860, John Wyeth and his brother Frank established a drugstore. Wyeth Inc. is the world's eight largest drug maker (2003), falling from the seventh position it had held for many year. 

Premarin tablets contain:   • estrone   • equilin   • 17 alpha-dihydroequilin   Together with smaller amounts:   • 17 alpha-estradiol   • equilenin   • 17 alpha-dihydroequilenin as salts of their sulfate esters