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 cyclooctyl acetate
Estradiol cyclooctyl acetate (ECoA), or estradiol 17β-cyclooctylacetate, also known as estra-1,3,5(10)-triene-3,17β-diol 17β-cyclooctylacetate, is a synthetic, steroidal estrogen and an estrogen ester – specifically, the 17β-cyclooctylacetate ester of estradiol – which has been studied for use in hormone replacement therapy for ovariectomized women and as a hormonal contraceptive in combination with a progestin but was never marketed. It has greater oral bioavailability than does micronized estradiol due to absorption via the lymphatic system and hence partial bypassing of first-pass metabolism. It is approximately twice as potent as micronized estradiol orally and has a comparatively reduced impact on liver parameters such as changes in sex hormone-binding globulin production.