Pharmacokinetics of estradiol
Estradiol can be administered in the form of a very long-lasting subcutaneous pellet implant. These implants are replaced once every 6 to 12 months, and can achieve high and very constant circulating levels of estradiol. They are surgically inserted by a trained physician in a medical office or clinic and can be placed into locations including the lower abdomen, lower back, buttocks, or hips. Subcutaneous implants containing 25, 50, and 100 mg estradiol for replacement usually once every 6 months are available as approved pharmaceutical medications. Up to 800 mg estradiol per implantation has been used. Pharmaceutical estradiol implants have been said to be used almost exclusively in the United Kingdom. An estradiol implant has not been approved by the FDA as a pharmaceutical medication in the United States, but hormone implants, including estradiol implants, are available as custom compounded products in this country.
Cloxestradiol acetate
Cloxestradiol acetate (brand name Genovul), also known as 17-(2,2,2-trichloroethoxy)estradiol "O","O"-diacetate, is a synthetic, steroidal estrogen derived from estradiol. It is the "O","O"-diacetate ester of cloxestradiol, which, in contrast to cloxestradiol acetate, was never marketed.