Estradiol stearate
Estradiol stearate (brand name Depofollan), or estradiol octadecanoate, is a naturally occurring steroidal estrogen and an estrogen ester – specifically, the C17β stearate ester of estradiol. It occurs in the body as a very long-lasting metabolite and prohormone of estradiol. In addition, estradiol stearate is or has been available as a pharmaceutical drug for use via depot intramuscular injection. The drug was introduced in 1941 as Depofollan and was the first long-acting estrogen, although it has never been widely used. It has been reported in at least one source to have a duration of at least one month.
Pharmacodynamics of estradiol
Estradiol is an estrogen, or an agonist of the nuclear estrogen receptors (ERs), the estrogen receptor alpha (ERα) and the estrogen receptor beta (ERβ). According to one study, the value of estradiol for the human ERα is 50 pM (0.05 nM) and for the human ERβ is 200 pM (0.2 nM). Estradiol is also an agonist of the membrane estrogen receptors (mERs), including the G protein-coupled estrogen receptor (GPER), G-coupled membrane estrogen receptor (G-mER), ER-X, and ERx. It is far more potent as an estrogen than are other natural and bioidentical estrogens like estrone and estriol. Given by subcutaneous injection in mice, estradiol is about 10-fold more potent than estrone and about 100-fold more potent than estriol.