Estradiol (medication)
Estradiol is also available in the U.S. in combination with progestogens for the treatment of menopausal symptoms and as a combined hormonal contraceptive:Estradiol and estradiol esters are also available in custom preparations from compounding pharmacies in the U.S. This includes subcutaneous pellet implants, which are not available in the United States as FDA-approved pharmaceutical drugs. In addition, topical creams that contain estradiol are generally regulated as cosmetics rather than as drugs in the U.S. and hence are also sold over-the-counter and may be purchased without a prescription on the Internet.
Polyestradiol phosphate
Polyestradiol phosphate (PEP), sold under the brand name Estradurin, is an estrogen medication which is used primarily in the treatment of prostate cancer in men. It is also used in women to treat breast cancer, as a component of hormone therapy to treat low estrogen levels and menopausal symptoms, and as a component of feminizing hormone therapy for transgender women. It is given by injection into muscle once every four weeks.
Common side effects of PEP include headache, breast tenderness, breast development, feminization, sexual dysfunction, infertility, and vaginal bleeding. PEP 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 in the form of a polymer and is an extremely long-lasting prodrug of estradiol in the body. The time it takes for 50% of a dose of PEP to be eliminated from the body is more than two months. Because PEP works by being converted into estradiol, it is considered to be a natural and bioidentical form of estrogen. The safety profile of parenteral estradiol esters like PEP is greatly improved relative to synthetic oral estrogens like ethinylestradiol and diethylstilbestrol.
PEP was discovered around 1953 and was introduced for medical use in the United States in 1957. Along with estradiol undecylate and estradiol valerate, it has been frequently used in the United States and Europe as a parenteral form of estrogen to treat men with prostate cancer. However, it is no longer available in the United States.