Estradiol (medication)
, estradiol is available in the United States in the following forms:Oral estradiol valerate (Progynova) and other esters of estradiol that are used by injection like estradiol benzoate, estradiol enantate, and estradiol undecylate all are not marketed in the U.S. Polyestradiol phosphate (Estradurin) was marketed in the U.S. previously but is no longer available.
Pharmacokinetics of estradiol
Polyestradiol phosphate is an ester prodrug of estradiol in the form of a polymer which is used via intramuscular injection primarily to treat prostate cancer, but also to treat breast cancer and menopausal symptoms. It has an extremely long duration of action, with a terminal half-life of about 70 days (10 weeks) following a single intramuscular administration of the medication. In addition, unlike most other estradiol esters, the estradiol levels achieved with polyestradiol phosphate are highly constant and uniform. Levels of estradiol in men with intramuscular injections of polyestradiol phosphate once every 4 weeks were about 350 pg/mL with 160 mg, 450 pg/mL with 240 mg, and almost 700 pg/mL with 320 mg, all measured after 6 months of treatment. Polyestradiol phosphate has been discontinued in many countries, and remains available today in only a few countries, mostly the Nordic countries of Europe.