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 cypionate
Estradiol cypionate is and has been available as an oil solution for intramuscular injection provided in vials and ampoules at concentrations of 1, 3, and 5 mg/mL (and containing 5, 10, 15, 25, or 50 mg estradiol cypionate total). The 1 and 3 mg/mL concentrations (containing 5 and 15 mg estradiol cypionate total) have been discontinued in the United States, but the 5 mg/mL concentration (containing 25 mg estradiol cypionate total) remains available. Aside from estradiol cypionate, the only other injectable estrogen formulations that remain available in the United States are estradiol valerate (10 mg/mL, 20 mg/mL, and 40 mg/mL in oil) and conjugated estrogens (25 mg/vial in solution).