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 progesterone
Progesterone does not appear to be available pharmaceutically in the form of subcutaneous pellet implants. This is in contrast to estradiol and testosterone. Progesterone may be available in the form of subcutaneous pellet implants from some compounding pharmacies however. Such products are not regulated for quality or effectiveness however. Subcutaneous implantation of progesterone has been studied in animals. Although progesterone is not available for subcutaneous implantation as a pharmaceutical product, subcutaneous implants of progestins, such as etonogestrel (Implanon/Nexplanon) and levonorgestrel (Jadelle/Norplant), are available as pharmaceutical preparations. They are used specifically as a form of long-lasting hormonal birth control.