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 acetate
Estradiol acetate, sold under the brand names Femtrace, Femring, and Menoring, is an estrogen medication which is used in hormone therapy for the treatment of menopausal symptoms in women. It is taken by mouth or given as a vaginal ring once every three months.
Side effects of estradiol acetate include breast tenderness, breast enlargement, nausea, headache, and fluid retention. Estradiol acetate is a synthetic estrogen and hence is an agonist of the estrogen receptor (ER), the biological target of estrogens like estradiol. It is an estrogen ester and a prodrug of estradiol in the body. Because of this, it is considered to be a natural and bioidentical form of estrogen.
Estradiol acetate was introduced for medical use in 2001. It is available in the United States and the United Kingdom. The formulation for use by mouth has been discontinued in the United States.