Fact Check


Is the drug Premarin produced from the urine of pregnant horses?

Published June 27, 2002


Claim:   The drug Premarin is produced from the urine of pregnant horses.

Status:   True.

Origins:   One of the inevitable aspects of the aging process in women is the decreased production of the hormones estrogen and progestin. A 40% to 60% drop-off in estrogen production generally occurs with the onset of menopause (or after some types of hysterectomies). Unfortunately, for many women these changes often


are accompanied by uncomfortable symptoms (such as hot flashes, night sweats, and vaginal dryness), and
estrogen loss is also linked to a significant increase in the incidence of heart disease, stroke, and osteoporosis.

Premarin (and Premarin-containing products such as Prempro, Premphase, and Prempac) is a drug used in hormone replace therapy HRT regimens prescribed for women to help lessen the symptoms of menopause and reduce the risk of heart disease, stroke, and osteoporosis. Premarin is available in several forms (pills, creams, injections, patches) and, as the name (a shortening of the phrase "pregnant mares' urine") suggests, contains conjugated estrogens obtained from the urine of pregnant mares.

Premarin is not unique as an animal-derived drug, of course, as generations of diabetics have been kept alive through injections of purified insulin obtained from the pancreases of cattle and pigs.

No real alternative to animal insulin was available until 1982, when the U.S. Food and Drug Administration approved the first synthetic insulin, Humulin.

The continued use of Premarin has generated controversy because of issues associated with the industrial use of animals required to produce a supply of the drug; information regarding concerns over the "pee line" collection of urine from mares to produce Premarin is available on a number equine advocacy web sites. (Although cattle and pigs were used as sources of insulin for diabetics, those animals were not specifically raised to be insulin producers; the insulin was obtained from animals raised and slaughtered for the beef and pork markets.)

The development of generic alternatives (such as Estrace, Estraderm, Ogen, OrthoEst, Estratab, Menest, Estinyl, Estrovirus, and OrthoDienestrol) and synthetic estrogens (such as Cenestin) has been cited as an advancement that eliminates the need for animal-derived estrogens such as Premarin for most women.

Last updated:   1 August 2007

David Mikkelson founded the site now known as snopes.com back in 1994.

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