Estradiol sulfate
As the sodium salt, sodium estradiol sulfate, E2S is present as a minor constituent (0.9%) of conjugated equine estrogens (CEEs), or Premarin. It effectively functions as a prodrug to estradiol in this preparation, similarly to E1S. E2S is also formed as a metabolite of estradiol, as well as of estrone and E1S. Aside from its presence in CEEs, E2S is not available as a commercial pharmaceutical drug.
Estriol (medication)
Following its discovery in 1930, estriol was introduced for medical use as an oral tablet in the 1930s. Emmenin and Progynon were oral estrogens that contained estriol conjugates, primarily estriol glucuronide, and were introduced in the 1930s. They were the first orally active estrogen preparations to be introduced in medicine. Estriol continues to be used medically today, widely throughout the world and in a variety of different formulations and brand names.