The checkered history of Pfizer’s Premarin family of drugs

The drugs

The name Premarin® spells out in its name what it is made from — PREgant MAres uRINe.

Pfizer’s Premarin® family of hormone replacement therapy drugs of today includes not only Premarin®, but also similarly manufactured pharmaceuticals — marketed at various times — under the names Prempro®, Premphase®, Provera® and later Aprela® (originally called Duavee or Duavive before its release). Add to the list Premplus which was developed by Wyeth until Pfizer came along and made them part of its empire.

Premarin®, Prempro® and Premphase® are typically prescribed to women to help reduce symptoms of menopause such as hot flashes and vaginal dryness.

Provera®, in combination with an estrogen-containing medicine, is used to relieve symptoms of menopause in women with an intact uterus. Provera® is also used to protect the lining of the uterus while the estrogens relieve the symptoms of menopause.

The menopausal-osteoporosis drug Aprela® is a combination of Premarin® and bazedoxifene. Bazedoxifene is a Selective Estrogen Receptor Modulator or SERM also known as Viviant® specifically developed to help prevent postmenopausal osteoporosis. 

The Premarin® family of drugs has a long and checkered history. Yet with all of the notoriety and multiple warnings these drugs have garnered over many years (not to mention class action lawsuits), doctors still prescribe them and women continue to take them.

The farms


The number of mares in PMU barns in North America has decreased significantly from an estimated high of 55-60,000 in the late 1990’s.

There are no PMU farms operating any longer in the United States. As of this writing, all that are left are a reported 1,300 mares on PMU farms in Canada, according to The North American Equine Ranching Information Council, or NAERIC.

NAERIC’s website tell us:

“There are 18 family-owned equine ranches that are members of NAERIC and contracted by Pfizer to collect pregnant mares’ urine (PMU). These equine ranches are located in the Canadian provinces of Manitoba (15) and Saskatchewan (3). All ranches are within reasonable proximity to Pfizer, in Brandon, Manitoba, where the initial PMU processing occurs.”

It continues, “Since equine ranchers are primarily horse breeders that are also involved in the collection of pregnant mares’ urine (PMU), the type and breed of horses found on equine ranches will vary depending on each rancher’s preference and breeding program.”


Enter China.

In 2016, the Fund for Horses discovered that there were PMU farms operating in China. These farms had been in production undetected by anyone outside of China for more than 10 years.

PMU Farm in Xinyuan County, China (2012).
PMU Farm in Xinyuan County, China (2012).

Tuesday’s Horse revealed:

“In 2005, a Chinese company — Xinjiang Xinziyuan Biological Pharmaceutical Co., Ltd. — was formed for the express purpose of creating a Chinese PMU industry based in northwest China’s Nilka County, located within the Ili Kazakh Autonomous Prefecture of the Xinjiang Uygur Autonomous Region.”

“Breeding of PMU mares and sales of pregnant mare’s urine has since become the ‘sunrise industry’ for the regional rural farm economy, providing a significant increase in income for the farmers and incentive to expand production and number of horses.”

“On one hand, Xinjiang Xinziyuan Biological’s founding purpose is to dominate Pfizer’s international Premarin market as a Chinese competitor, while on the other hand Pfizer is said to be the primary contractor for pregnant mare’s urine produced by the ‘sunrise industry’ that Xinjiang Xinziyuan Biological’s created, and which supplies Pfizer with the pregnant mare’s urine to manufacture the Premarin products.”

Game. Set. Match.

The horses

Premarin® mares are typically large bred horses such as a Belgian—Quarter Horse cross, prized for their large bladders.

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

Pregnant Mares on the “Pee Line”. Source unknown.

Mares are taken off the “pee line” a couple of months before they foal and turned out to give birth. The mares are able to nurse their foals until weaning age, about 4 months. Then their foals are taken away from them, and the mares are re-impregnated.

When the mares can no longer conceive their destination is the slaughterhouse. Foals born to these mares are worth less than the urine their mothers produce to a PMU farmer, so he sends unwanted foals to a slaughter auction to be sold for their meat.

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.”

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. A colt foal has less than 1-in-50 chance of not being sent to slaughter.

The lawsuits

Questions about links between Premarin® and Prempro® and the development of various cancers including breast and ovarian — as well as other life threatening conditions, such as stroke and heart disease — led to a decline in the use of these drugs well over a decade ago.

Still, the true source of the drugs’ ingredients is still unknown to the many menopausal women seeking relief from “change of life” symptoms.

Law book and gavel. Uncredited Image.
Law book and gavel. Shutterstock.


In September 2020, it was reported:

“Prempro HRT has been proven to cause serious health risks in women, most notably breast cancer. Before 2002, it was believed that Prempro and other HRT therapies protected women against heart disease and osteoporosis and helped to treat symptoms of menopause. Instead, a federal study found that Prempro hormone replacement therapy increases the incidence of breast cancer by 26 percent, including heart attack by 29 percent, stroke by 41 percent and blood clots in the legs and veins by 105 percent.”

“Pfizer has agreed to pay about $330 million to settle more than 2,200 lawsuits charging its Prempro hormone replacement therapy caused women to develop breast cancer, embracing a strategy used by several other drugmakers to cap the cost of growing product-liability litigation that can worry investors. The cases settled for an average of about $150,000, according to Bloomberg News, which first reported the settlement, although a Pfizer spokesman disputed the figures.”


As far back as 2009, a Philadelphia jury ordered Pfizer to pay $28 million in punitive damages, and $6.3 million in compensatory damages to a breast cancer survivor who used a trio of the company’s hormone replacement drugs, i.e. Premarin, Prempro and Provera.

Concerning a California class action suit, reports:

“On March 13, 2020, the Court entered an Order granting the Motion for Preliminary Approval of the proposed $200 million Class Action Settlement with Wyeth* and Wyeth Pharmaceuticals Inc.”

“The Class Action Settlement includes all California consumers who purchased Wyeth’s Hormone Replacement Therapy products, Premarin, Prempro, and/or Premphase, for personal consumption between January 1995 and January 2003, and who do not seek personal injury damages resulting from their use of Premarin, Prempro, and/or Premphase.”

*In January 2009, Pfizer announced it was to acquire Wyeth, “Creating the world’s premier biopharmaceutical company.”

See Top Class Actions »

The marketing


The 1960s saw skyrocketing sales of Premarin, pushed by a hugely successful campaign called “Keep her on Premarin.”

One ad, titled “Husbands, too, like Premarin,” states, “The physician who puts a woman on Premarin when she is suffering in menopause usually makes her pleasant to live with once again.”

Seaman 2003

Makes her pleasant to live with once again?

The ad continues, “It is no easy thing for a man to take the stings and barbs of business life, then to come home to the turmoil of a woman ‘going through the change of life.’ If she is not on ‘Premarin,’ that is.”

Women were also targeted directly.

Hormone replacement therapy, it was claimed, would enable women to preserve their youth, vigour, mental acuity and sexual attractiveness”.

A book by British gynecologist Robert Wilson, titled Feminine Forever, became a bestseller when it was released in 1966. It helped convince millions of women that estrogen replacement around menopause wasn’t just a helpful way to relieve symptoms, but something necessary to protect their very identities as women.

Wilson wrote, “Every woman alive today has the option of remaining feminine forever.” He compared post-menopausal women to castrated men but said there was hope. By taking estrogen, her “breasts and genital organs will not shrivel.”

We think that is a good place to leave it.

Related Reading

A look at a PMU farm in China — and it’s not all about Pfizer, Tues Hrse, (Sept 21, 2016) »

Premarin—How Marketing Popularized Treatment for Menopausal Symptoms, The Great Courses Daily, Lecture Series »

A time of change: a history of our understanding of the menopause, History Extra (June 28, 2021) »

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Featured Image: Pfizer Corporate HQ, New York

4 thoughts on “The checkered history of Pfizer’s Premarin family of drugs”

  1. It is beyond my comprehension how…HOW these men..these these Canadian businesses and the slaughter house monsters….how can they do these terrible things to all those helpless, gentle, kind, loving animals. I derive some comfort knowing they will some day meet their maker and know his wrath. I just wish he’d speed it up. I’d want a front row seat.


  2. What many people, including many who are knowledgeable about the former PMU horror, do not realize is that the remaining fertile mares formerly used for producing urine (as well as hundreds if not thousands of newer “production” mares) are birthing foals SPECIFICALLY for east Asian countries’ slaughter markets. These babies are raised to somewhere between the ages of weaning and yearling, then are shipped to the far east for MEAT. Given the levels of horrific cruelty involved in slaughtering animals for meat per the so-called “cultural beliefs” prevalant in those countries, the shipping event is probably not the worst of what they will experience before the blessed relief of death. Bottom line, the Canadian farms are still very much in the horse business – that would be the lucrative business of selling for slaughter. Laddieluv, I have to agree with your comment because I, too, hate too many people. Moreover, at my age I am so, so, tired of feeling so much anger and anguish over the revelations of such insane cruelty in this world toward animals when there is absolutely nothing I personally can do about it. I was lucky enough to have for many years a PMU baby, he was one of the last to make it out of Canada at side with his mother. A rescue group located in Oregon in those days brought I think it was several thousand mares out of Canada, many still with nursing foals. As for my gelding, a better horse never graced this sorry planet, but sadly he was lost to cancer at age 18. I fail to understand how these Canadian “horse farmers” can sleep at night or look at their own faces in the mirror for the shame of this ongoing insane cruelty. Canada, you have so much disgraceful history to answer for and not just regarding horses.


  3. It was a dark, cruel secret for a long time. You had no way of knowing. We knew nothing about it until we started the Fund for Horses.

    Liked by 1 person

  4. ..the hell of it..
    back in the 70’s, I took Premarin..
    ..I had no idea of the torture and horror from whence it came..
    I stopped cold/turkey after my child was born..
    ..never took it again..
    now knowing I contributed to this murder and hell for precious animals makes me so ill..
    ..I have no words..
    only heart break for the animals..

    am now vegan and cruelty free..
    ..the least I can do..

    ..I hate (too many) people..

    Liked by 2 people

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