# Pregnant Mare's Urine
**URL:** https://boards.straightdope.com/t/pregnant-mares-urine/101213
**Category:** Factual Questions
**Created:** [April 1, 2002, 4:02pm UTC](https://boards.straightdope.com/t/pregnant-mares-urine/101213 "2002-04-01T16:02:28Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@SharonLeigh](https://boards.straightdope.com/u/SharonLeigh)
#### Post date: [April 1, 2002, 4:02pm UTC](https://boards.straightdope.com/t/pregnant-mares-urine/101213/1 "2002-04-01T16:02:28Z")
I know that pregnant mare’s urine is used in some forms of Hormone Replacement Therapy, but is it also used in oral contraceptives?
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### Author:  [@Tranquilis](https://boards.straightdope.com/u/Tranquilis)
#### Post date: [April 1, 2002, 4:21pm UTC](https://boards.straightdope.com/t/pregnant-mares-urine/101213/2 "2002-04-01T16:21:44Z")
I’m going to give a very partial answer here:
Yes.
I’ve forgotten some of the details, So I’ll have to go look it up, but I recall a story about an oral contraceptive that went generic, and the generic pharma company making the low-cost version was using chemically synthesized hormones vice mare-urine extract, only to find that the resultant drug was less efficatious than the ‘real thing’. There was an active ingredient in the pregnant mare’s urine that everyone had missed. This resulted in a mad scrable to find and isolate the pharmacokinetic element.
I’ll look up the specifics, such as drug and manufacturer, for you in a bit…
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### Author:  [@Tranquilis](https://boards.straightdope.com/u/Tranquilis)
#### Post date: [April 1, 2002, 5:32pm UTC](https://boards.straightdope.com/t/pregnant-mares-urine/101213/3 "2002-04-01T17:32:09Z")
Here’s a quick over-view on [Ovarian Hormone Therapy](http://www.oxford.net/~tishy/whichoht.html). Included in this page is a link to [Conjugated Estrogens](http://www.rxlist.com/cgi/generic/conest.htm), specifically, Premarin®:
> [@](#):
>
> Conjugated estrogens is a mixture of estrogens obtained exclusively from natural sources, occurring as the sodium salts of water-soluble estrogen sulfates blended to represent the average composition of material derived from pregnant mares’ urine. It contains estrone, equilin, and 17 a-dihydroequilin, together with smaller amounts of 17 a-estradiol, equilenin, and 17 a-dihydroequilenin as salts of their sulfate esters.
This is for hormone therapy, of course, but further digging reveals [this letter](http://www.fda.gov/cder/news/celetterjw.htm) from the FDA IRT the unknown active ingredients in Premarin (PREgnant MARe urINe), rejecting all new applications for generic/synthetic conjugated estrogens until such time as those active ingredients are understood. [Here](http://www.fda.gov/cder/news/cebackground.htm) is an FDA “Backgrounder” on conjugated estrogens.
It appears that my memory was partially off… Premarin is sometimes prescribed _in addition to_ contraceptives to combat such side effects of contraceptives as vaginal dryness, but not as part of the primary contraceptive treatment.