Vintage Premarin ad from the days when it was made by Ayerst.

Premarin: The horses, the drugs, the women

Premarin-Expendable Artwork with Woman, Mare and Foal
Click to view full size. Free to use.


Premarin mares are large bred horses such as Belgian—Quarter Horses crosses, prized for their large bladders.

For most of their 11-month pregnancies, these horses are confined to stalls so small that they cannot turn around or take more than one step in any direction.

The mares must wear rubber urine-collection bags at all times which causes chafing and lesions.

The mares are taken off the pee line a couple of months before they foal.

Once the foals are born, the mares are re-impregnated; this cycle continues for about 12 years.

Sadly, the foals born to these mares are usually worth less than the urine their mothers produce. To the PMU farmers, they are worth more dead than alive.

Just as the male calves born to dairy cows are considered to be a byproduct of the dairy industry, the foals of PMU mares are considered to be nothing more than a living byproduct of Premarin.

Some foals will die soon after birth. Of those whom survive, the majority of them will be sent to auction where they will be sold for slaughter.

A filly foal has a less than 1-in-10 chance of not being sent to slaughter. Some will be kept to replace the worn-out mares on the PMU farms; the rest will be sent to the slaughter auction. A colt foal will have a less than 1-in-50 chance of not being sent to slaughter.

One PMU industry insider says, “See, the foals—and the mares which [sic] can’t get pregnant any more—they are the byproduct of the PMU industry . . . We crush ’em and recycle ’em, just like [aluminum] cans.”


The most commonly known drugs derived from the estrogen rich urine of pregnant mares (PMU) are the Premarin family of drugs.

The active ingredient is correctly referred to as conjugated equine estrogen (CEE).

Premarin is a hormone replacement therapy (HRT) drug introduced in 1942 for the relief of menopausal women. Today, it is the most widely-prescribed drug for women in North America with a reported 9 million American women currently taking some form of Premarin.

Premarin was formerly manufactured by Wyeth. Wyeth merged with Pfizer in 2009 and is now a Division of this pharmaceutical giant.

The Premarin family of drugs now includes Premarin (tablet and cream), Prempro, Premphase, and the recently approved Duavee (called Aprela during the FDA approval process and changed in the final hour to Duavee).

Many women taking the Premarin family of drugs—and alarmingly the doctors prescribing them—are unaware of the cruelty behind the making of these HRT drugs.

When Premarin was first released the active ingredient was commonly referred to as “conjugated equine estrogen”. The word “equine” has since been removed and they simply refer to it as “conjugated estrogen”, a way of hiding the true nature of these drugs and how they are produced.

It is critical that we step up immediately and inform doctors and warn women about the Premarin family of drugs, especially the latest of these, Duavee—and free the horses from their making.


In 2002, the Women’s Health Initiative (WHI) study of more than 16,000 women using Prempro, was abruptly halted by the federal government after it concluded that HRT raises a woman’s risk of having a stroke by 41 percent, risk of suffering a heart attack by 29 percent, and risk of getting breast cancer by 26 percent.

Dr. Claude Lenfant—director of the National Heart, Lung, and Blood Institute, which sponsored the study—said the cardiovascular and cancer risks were “too high a price to pay” and urged women who want to ward off heart disease to “focus on well-proven treatments” instead, such as controlling blood cholesterol and keeping their weight down.

The WHI also found that Prempro has no meaningful effects on women’s physical or emotional health, pain levels, memory, sleeping patterns, or energy levels. The researchers concluded that Prempro is effective for short-term relief from hot flashes but nothing else.

Many women find that they can control hot flashes and other menopausal symptoms by making easy lifestyle changes—like eating a low-fat vegetarian diet and getting regular exercise—rather than contributing to animal suffering. Dr. Jennifer Hays from the Baylor College of Medicine commented, “The average woman will not experience an improvement in her quality of life by taking this pill.”

At the time of this writing, Wyeth (now a division of Pfizer) faces more than 5,000 personal injury lawsuits filed by more than 8,000 women who took Prempro or Premarin.

Please support March for Premarin Horses through the Premstoppers Campaign with a donation.

Please feel free to copy and use the artwork at the top of this page. These drugs are advertised for sale online with and without prescription.

9 thoughts on “Premarin: The horses, the drugs, the women”

  1. I was Rx Premarin after a hysterectomy. Used it for a couple of months. Then I did the research and found out about the horses. I immediately went to my GYN and asked to be taken off this medication. There are alternatives.


  2. I see that your blog post only addresses women suffering with side effects of menopause, what is your proposed solution for those women who are young (<30 years old) and have low estrogen levels?

    As an example, what is your proposal for a young woman with Asherman's Syndrome recovering from hysteroscopic adhesiolysis with the hope that she will someday be able to conceive?

    This example is my situation, I took high dose Premarin for 40 days while recovering from surgery. Hopefully I will now be able to conceive.

    I am well aware of where Premarin comes from, and while the situation may not be ideal for these animals, neither in my opinion, is the situation for medium to large sized dogs living in city apartments. Additionally, I'm keenly aware of the difficulty and frustration of women my age who need treatment but are often faced with apathy from medical doctors as out symptoms are very similar to menopause yet we are not menopausal.

    Finally, veterinarians in North America (both Canada and the United States) have reported on PMU mares (see: and continue to monitor the welfare of these animals.


    1. NAERIC are paid by Pfizer. What else are they going to say? Most of the Premarin mares and foals have been moved away from North America to countries like China.

      Perhaps you may want to consider alternative drugs. We are not doctors so cannot suggest what they might be in circumstances such as yours.

      But surely you do not consider the slaughter of byproduct foals with people keeping dogs in apartments.

      You must decide according to your own conscience. At the same time do not throw stones at those who are working to save these horses from a horrible life and possible death.

      Thank you for writing. We now understand even more about how these drugs are being used. Transgenders have taken an alarming amount of these drugs and suffered the consequences. We are just learning about their plight too. Premarin is typically an HRT drug and prescribed as such. We understand it is also used for osteoporosis relief.

      We wish you well.


  3. Reblogged this on and commented:
    My precious Cass came from a defunct PMU farm in Canada. I cannot say for sure she was actually used in the pee barns but I do know she was used as a baby machine. Her body cannot hide the long-term effects of assembly line births. I do my best to make up for it. She is one of the lucky ones, she got out alive. Her unborn (at the time) foal is one of the lucky ones, she is alive and well and about to turn 6! Her herd stallion, Marvin, is one of the lucky ones as we liberated him a year after her. The bottom line is, not only is this bad for the horses it’s unsafe for women.


  4. In addition to the cruelty there is, as you mentioned, the risk of breast cancer. I have a good friend who had breast cancer and she attributes it to Premarin. In regard to the effects of menopause – hot flashes etc. are not inevitable. I never suffered from any side effects of menopause. Im a vegetarian and maybe that helped. Also I think to many American women are conditioned to expect problems with menopause. None exist in many developing countries.



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