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.
Estradiol benzoate
Estradiol benzoate is available in Europe and in other parts of the world. It was previously available for medical use in the United States, but is no longer marketed in this country. However, it is approved and marketed in the United States for veterinary use as a subdermal implant both alone and in combination with the androgen/anabolic steroid trenbolone acetate (brand names Celerin and Synovex, respectively). Outside of the United States, estradiol benzoate is also marketed in combination with progesterone for use as an intramuscular injection.