Daughters of Premarin®: The Generics


FURTHER to the reference of generics in the “Alternatives to Drugs Made with Pregnant Mare’s Urine”, I think a separate word on the availability of generic Premarin® and its daughter drugs is warranted to clear up any confusion for those seeking to avoid products manufactured from the urine of pregnant mares.

Premarin has a long and interesting history when it comes to FDA approval of generics, a history mired in the ruthless and bloodthirsty battle of Big Pharma patent wars.

Many years ago, in 1986, the effectiveness of Premarin®’s, and other short-term acting estrogens, ability to diminish bone loss associated with osteoporosis was granted approval by the FDA. What was once a drug that was prescribed for the relief of menopausal symptoms now became the panacea for a long-term chronic problem. [1]  And with this came a huge untapped market.

At this time there were certified generics that were interchangeable with Premarin®.  However because of the ramifications of long-term use, the science behind the drugs prevailed.

While Premarin® provided slow-release bioavailability, the generics were immediate release. This disparity in mode of release would turn into a long battle between the generic manufacturers, Wyeth-Ayerst and the FDA. [2]

To make a long story short, the outcome of detailed analysis showed that the bioavailability of generic versions was not equivalent to Premarin® and in 1991 the FDA withdrew approval of all ANDAs (Abbreviated New Drug Applications) proclaiming that none of the synthetics on the market could be considered generic versions of Premarin®. [3]

Because of the lucrative market potential, two generic manufacturers – Duramed and Barr – set out to develop products that solved the bioavailability problem and submitted ANDAs for FDA approval. Both met the requirements of adsorption efficiency however Wyeth had been conducting its own research and contested FDA approval on the grounds that the generic drug lacked one of the estrogens, called delta 8,9 (dehydroestrone sulfate), present in Premarin®.

Nevertheless, in 1994, the FDA unanimously ruled that delta 8,9 (dehydroestrone sulfate) was an impurity and not a required ingredient of a generic version.

Duramed applied for FDA approval of Cenestin in September 1995, and Barr followed the next July. [4]  

What happened next effectively blocked any competitor from manufacturing a generic Premarin®. Propaganda and political persuasion tactics were used to coerce the FDA and in 1995 Wyeth-Ayerst successfully petitioned the FDA to require the presence of delta 8,9-dehydroestrone in any generic version of Premarin®. [5]  Together with Wyeth-Ayerst’s patent on synthetic delta 8,9-dehydroestrone, this shut out the competitors.

Eventually Duramed filed a NDA (New Drug Application) for its synthetically derived estrogen Compound Cenestin which is still available on the market today along with a variety of other synthetic products, none of which contain pregnant mare’s urine.

Premarin® lost its patent in February 2012 and the patent for Prempro® held by Wyeth Pharmaceuticals, does not expire until early 2015. 

Despite Premarin’s® patent expiration there seems to be no interest in manufacturing a generic version from pregnant mare’s urine. [6]  In any case, it would be challenging for another pharmaceutical company to synthesize a medication that is similar enough to Premarin® to receive the approval of the FDA, similarly so for Prempro® as it contains the same natural conjugated equine estrogens as Premarin®.

The so-called Premarin generics are the lab-synthesized versions manufactured from plant sources not pregnant mare’s urine (see “Alternatives to Drugs Made with pregnant Mare’s urine). [7] 

As a reminder, these drugs carry with the same serious risks as the Premarin® family of drugs.

Some will say that generic Premarin® is available online without prescription, particularly from Canada. However be wary of any medications that tout themselves as being a safe generic version of Premarin®. Congressional testimony from the US FDA points out the dangers of inadequately regulated foreign Internet sites which have also become portals for unsafe and illegal drugs. This excerpt specifically targets Canadian generic websites: [8]

“A recent example illustrates some of the dangers associated with the purchase of prescription drugs from rogue pharmacy sites. Within the last six months, FDA has examined two web sites having identical web pages headlined “Canadian Generics” which were identified through spam e-mails sent to consumers.  FDA has purchased prescription drugs from both of these sites, and has found that these drugs and the manner in which they are sold pose potential threats to the health and safety of consumers.

There is at least one Canadian flag on every page of these sites, as well as the words “Canadian Generics.”  The web sites say, “Order Canadian to get the biggest discounts!”  Both of the URLs from which the orders were placed suggest the sites are located in, and operated out of, Canada. Despite these representations, however, we determined there is no evidence that the dispensers of the drugs or the drugs themselves are Canadian. The registrants, technical contacts, and billing contacts for both web sites have addresses in China.”

There is currently no therapeutically equivalent version of Premarin® available in the United States.  In other words, there is no approved generic for Premarin in the US.

The drug policies and generic approval practices in other countries may vary. What is a generic in one country may not be approved as one in another.

Fraudulent online pharmacies may attempt to sell an illegal generic version of Premarin®. These medications may be counterfeit and potentially unsafe.

If you purchase medications online, be sure you are buying from a reputable and valid online pharmacy. [9]

Consult Your Doctor

Always consult your doctor before embarking on any change in medication


[1]  http://pubs.acs.org/subscribe/archive/mdd/v03/i08/html/kling.html
[2]  Same as at 1.
[3]  Same as at 1.
[4]  http://www.sagepub.com/jowett5estudy/cases/77821_c2.pdf
[5]  Same as at 4.
[6]  http://www.drugs.com/availability/generic-premarin.html
[7]  http://www.horsefund.org/pmu-alternatives-to-cee-drugs.php
[8]  http://www.fda.gov/newsevents/testimony/ucm113635.htm
[9]  Same as at 6.


The Quest for a Generic Premarin – A Bitter Pill to Swallow, By JANE ALLIN, Tuesday’s Horse, Nov. 14, 2014 »

Pregnant Mare’s Urine Images


PMU farm in Xinyuan County

PMU Farm in Xinyuan County, China (2012). Slide 1.
PMU Farm in Xinyuan County, China (2012). Slide 2.
PMU Farm in Xinyuan County, China (2012). Slide 3.
PMU Farm in Xinyuan County, China (2012). Slide 4.
PMU Farm in Xinyuan County, China (2012). Slide 5.
PMU Farm in Xinyuan County, China (2012). Slide 6.
PMU Farm in Xinyuan County, China (2012). Slide 7.
PMU Farm in Xinyuan County, China (2012). Slide 8.
Chinese version of Premarin cream.


There are no longer any PMU farms in the U.S. However, there are a reported 19 “pee farms” remaining in Canada although NAERIC’s website states:

“There are 24 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 (19) and Saskatchewan (5). All ranches are within reasonable proximity to Pfizer, in Brandon, Manitoba, where the initial PMU processing occurs”.

While there are no images available to the public of what the inside of these farms look like that we can find, here are some of the byproduct horses.

Belgian horses awaiting shipment to Japan from Canada to Japan for slaughter. Live horses exported to Japan are killed for a specific foodstuff: a kind of specialty sashimi called basashi.
Horses loaded and waiting on the tarmac in Canada for live transport to Japan for slaughter for human consumption. Canadian Horse Defence Coalition image.
Activist photo taken at the Calgary Airport in 2017 show four draft horses per crate, a practice which was banned by the CFIA five years ago. Canadian Horse Defence Coalition image.
A PMU mare and her foal.

Vintage Images

Sanitized picture released by the USDA.
A “Pee Line”, Canada. Brenda Hunter photo.
PMU Farm. Winnipeg, Canada.
PMU Farm. N. America.
PMU Farm. N. America.

Featured Image: Grey Draft Horse. Horse Illustrated.

THF 2019 Logo. ©The Horse Fund.

Where will Wyeth’s horses go?

Pharmaceutical giant Wyeth puts thousands of horses at risk of slaughter with announcement of massive PMU farm closures

Wyeth logo. Google image.

Houston, Texas (Apr. 27, 2005) – Wyeth Pharmaceuticals sounds a death knell for thousands of horses with its recent announcement that it is significantly reducing production of its hormone replacement therapy drugs for women made from pregnant mare’s urine.

Wyeth just announced its closure of 19 pregnant mare urine farms in Alberta, Canada and approximately 30 more ranches in Manitoba, Saskatchewan and North Dakota. This will displace around 30,000 mares altogether, almost all of which are pregnant.

During the last layoff due to the downsizing of the industry due to rapidly declining demand for Wyeth’s Premarin® family of drugs, nearly 15,000 horses were put “out of work.” Although some were bought or found homes, a high percentage of the mares and foals went to slaughter.

In the United States, much is being made about the so-called “unwanted horse” in reaction to pending legislation in Congress that would ban horse slaughter. This culminated in a summit meeting recently hosted in Washington DC by the American Association of Equine Practitioners to discuss what should be done with America’s surplus horses.

Pharmaceutical giant Wyeth, who has earned billions of dollars since the 1950s from the sale of its Premarin® family of drugs made from pregnant mare’s urine, is once again burdening the equine communities in both the U.S. and Canada with thousands of its redundant horses. However, the Unwanted Horse Summit did not address the problem of the thousands of horses unwanted by Wyeth.

“It would be highly beneficial if the AAEP would place issues like the sudden dumping of thousands of horses no longer wanted by Wyeth on the Summit meeting’s agenda,” comments Vivian Farrell, President of the Int’l Fund for Horses. “Failing to address situations like these takes away credibility from these sorts of proceedings.”

Where will Wyeth’s unwanted horses go?

As in the past, it will be publicly supported horse rescues and shelters who will have to intervene if the majority of these horses are not to end up in the horse slaughter plants of the U.S. and Canada, and subsequently on someone’s dinner plate in Europe and Japan.

“We are calling on Wyeth to come up with a workable plan and the capital to provide for the care and maintenance of its mares and foals until appropriate homes are found for them,” states Sinikka Crosland, Executive Director of the Canadian Horse Defence Coalition. “It is high time Wyeth took real responsibility for theses horses and provided the much needed support to those of us willing to do this work.”

THF 2019 Logo. ©The Horse Fund.