Estradiol acetate (EA), 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 once daily or given as a vaginal ring once every three months.
Norethisterone acetate (NETA), also known as norethindrone acetate and sold under the brand name Primolut-Nor among others, is a progestin medication which is used in birth control pills, menopausal hormone therapy, and for the treatment of gynecological disorders. The medication available in low-dose and high-dose formulations and is used alone or in combination with an estrogen. It is taken by mouth.
Estradiol cypionate (EC), sold under the brand name Depo-Estradiol among others, is an estrogen medication which is used in hormone therapy for menopausal symptoms and low estrogen levels in cis women, in hormone therapy for transgender women, and in hormonal birth control for cis women. It is given by injection into muscle once every 1 to 4 weeks.
Estradiol undecylate (EU), also known as estradiol undecanoate and formerly sold under the brand names Delestrec and Progynon Depot 100 among others, is an estrogen medication which has been used in the treatment of prostate cancer in men. It has also been used as a part of hormone therapy for transgender women. Although estradiol undecylate has been used in the past, it was discontinued and hence is no longer available. The medication has been given by injection into muscle usually once a month.
An estrogen ester is an ester of an estrogen, most typically of estradiol but also of other estrogens such as estrone, estriol, and even nonsteroidal estrogens like diethylstilbestrol. Esterification renders estradiol into a prodrug of estradiol with increased resistance to first-pass metabolism, slightly improving its oral bioavailability. In addition, estrogen esters have increased lipophilicity, which results in a longer duration when given by intramuscular or subcutaneous injection due to the formation of a long-lasting local depot in muscle and fat. Conversely, this is not the case with intravenous injection or oral administration. Estrogen esters are rapidly hydrolyzed into their parent estrogen by esterases once they have been released from the depot. Because estradiol esters are prodrugs of estradiol, they are considered to be natural and bioidentical forms of estrogen.
Hexestrol, sold under the brand name Synestrol among others, is a nonsteroidal estrogen which was previously used for estrogen replacement therapy and in the treatment of certain hormone-dependent cancers as well as gynecological disorders but is mostly no longer marketed. It has also been used in the form of esters such as hexestrol diacetate and hexestrol dipropionate. Hexestrol and its esters are taken by mouth, held under the tongue, or via injection into muscle.
Cloxestradiol (INN), also known as 17-(2,2,2-trichloroethoxy)estradiol, is a synthetic, steroidal estrogen which was never marketed. It is an analogue of estradiol with a 2,2,2-trichloroethoxy substitution. The O,O-diacetate derivative, cloxestradiol acetate, has been marketed as an estrogen.
Estradiol stearate (E2-17-St), also known as estradiol octadecanoate and sold under the brand name Depofollan, is a naturally occurring estrogen and an estrogen ester – specifically, the C17β stearate ester of estradiol. It occurs in the body as a very long-lasting metabolite and prohormone of estradiol. The compound is one of the components that collectively constitute lipoidal estradiol, another of which is estradiol palmitate. It is extremely lipophilic and hydrophobic. Estradiol stearate has no affinity for the estrogen receptor, requiring transformation into estradiol via esterases for its estrogenic activity. The compound does not bind to sex hormone-binding globulin or α-fetoprotein, instead being transported by lipoproteins such as high-density lipoprotein and low-density lipoprotein.
Estradiol pivalate, also known as estradiol trimethyl acetate and sold under the brand name Estrotate, is an estrogen medication and an estrogen ester; specifically, the C3 pivalic acid ester of estradiol. It was marketed as an oil solution for intramuscular injection in the 1940s and 1950s. A combination of estradiol pivalate (1 mg/mL) and progesterone (10 mg/mL) in oil solution for intramuscular injection was available in 1949.
Estriol acetate benzoate (JAN), or oestriol diacetate benzoate (BAN), is an estrogen medication. It is an estrogen ester, specifically, an ester of estriol.
Estrone acetate is a semisynthetic, steroidal estrogen. It is an estrogen ester, specifically, an ester of estrone.
Hydroxyestrone diacetate, or 16α-hydroxyestrone diacetate, also known as 3,16α-dihydroxyestra-1,3,5(10)-trien-17-one 3,16α-diacetate, is a synthetic, steroidal estrogen which has been marketed in France, Spain, Brazil, and Argentina. It is a derivative of 16α-hydroxyestrone with an acetate esters attached at the C3 and C16α positions.
A progestogen ester is an ester of a progestogen or progestin. The prototypical progestogen is progesterone, an endogenous sex hormone. Esterification is frequently employed to improve the pharmacokinetics of steroids, including oral bioavailability, lipophilicity, and elimination half-life. In addition, with intramuscular injection, steroid esters are often absorbed more slowly into the body, allowing for less frequent administration. Many steroid esters function as prodrugs.
Estradiol 3-propionate, or 3-propanoylestradiol, also known as estra-1,3,5(10)-triene-3,17β-diol 3-propionate, is a semisynthetic, steroidal estrogen that was never marketed. It is an estrogen ester, specifically, a propionic acid ester of estradiol, and acts as a prodrug to it in vivo. The chemical structure of estradiol 3-propionate is contained within estradiol dipropionate, estrapronicate, and orestrate, all of which are also estradiol esters.
Estradiol mustard, also known as chlorphenacyl estradiol diester, as well as estradiol 3,17β-bis(4- phenyl)acetate, is a synthetic, steroidal estrogen and cytostatic antineoplastic agent and a chlorphenacyl nitrogen mustard-coupled estrogen ester that was never marketed. It is selectively distributed into estrogen receptor (ER)-positive tissues such as ER-expressing tumors like those seen in breast and prostate cancers. For this reason, estradiol mustard and other cytostatic-linked estrogens like estramustine phosphate have reduced toxicity relative to non-linked nitrogen mustard cytostatic antineoplastic agents. However, they may stimulate breast tumor growth due to their inherent estrogenic activity and are said to be devoid of major therapeutic efficacy in breast cancer, although estramustine phosphate has been approved for and is used in the treatment of prostate cancer.
Lipoidal estradiol (LE2) is the variety of endogenous C17β long-chain fatty acid esters of estradiol which are formed as metabolites of estradiol. Important examples of these esters include estradiol arachidonate, estradiol lineolate, estradiol oleate, estradiol palmitate, and estradiol stearate. LE2 are estrogens but do not bind to the estrogen receptor, instead acting as prohormones of estradiol. Relative to estradiol, they have far longer-lasting durations of effect due to their much slower rates of metabolism and clearance. It has been hypothesized that LE2 may serve as a store of estrogen for when estradiol levels become low. LE2 are highly lipophilic and hydrophobic and are found in highest concentrations in adipose tissue and other estrogen-sensitive tissues and in low but detectable concentrations in circulation, with none excreted in urine. They have been referred to as the "endogenous counterparts of the synthetic esters of estrogens" like estradiol valerate and estradiol cypionate.
