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.
Pharmacokinetics of estradiol
Polyestradiol phosphate is an ester prodrug of estradiol in the form of a polymer which is used via intramuscular injection primarily to treat prostate cancer, but also to treat breast cancer and menopausal symptoms. It has an extremely long duration of action, with a terminal half-life of about 70 days (10 weeks) following a single intramuscular administration of the medication. In addition, unlike most other estradiol esters, the estradiol levels achieved with polyestradiol phosphate are highly constant and uniform. Levels of estradiol in men with intramuscular injections of polyestradiol phosphate once every 4 weeks were about 350 pg/mL with 160 mg, 450 pg/mL with 240 mg, and almost 700 pg/mL with 320 mg, all measured after 6 months of treatment. Polyestradiol phosphate has been discontinued in many countries, and remains available today in only a few countries, mostly the Nordic countries of Europe.