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.
Estradiol phosphate
Estradiol phosphate, or estradiol 17β-phosphate, also known as estra-1,3,5(10)-triene-3,17β-diol 17β-(dihydrogen phosphate), is an estrogen which was never marketed. It is an estrogen ester, specifically an ester of estradiol with phosphoric acid, and acts as a prodrug of estradiol in the body. It is rapidly cleaved by phosphatase enzymes into estradiol upon administration. Estradiol phosphate is contained within the chemical structures of two other estradiol esters, polyestradiol phosphate (a polymer of estradiol phosphate) and estramustine phosphate (estradiol 3-normustine 17β-phosphate), both of which have been marketed for the treatment of prostate cancer.