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.
Estradiol/megestrol acetate
Estradiol/megestrol acetate (E2/MGA), sold under the brand names Mego-E and Chinese injectable No. 2, is a form of combined injectable birth control which is used in the People's Republic of China. It contains 3.5 mg estradiol (E2), an estrogen, and 25 mg megestrol acetate (MGA), a progestin. It is a microcrystalline aqueous suspension with a defined particle size range. The medication is given once per month by injection into muscle.