|Trade names||Delestrec, Progynon Depot 100, others|
|Other names||EU; E2U; Estradiol undecanoate; Estradiol unducelate; RS-1047; SQ-9993|
|Drug class||Estrogen; Estrogen ester|
|Bioavailability||IM injection: High|
|Protein binding||Estradiol: ~98% (to albumin and SHBG)|
|Metabolism||Cleavage via esterases in the liver, blood, and tissues|
|Metabolites||Estradiol, undecanoic acid, estradiol metabolites|
|Duration of action||IM injection:|
• 10–12.5 mg: 1–2 months
• 25–50 mg: 2–4 months
|CompTox Dashboard (EPA)|
|Chemical and physical data|
|Molar mass||440.658 g/mol g·mol−1|
|3D model (JSmol)|
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.
Side effects of estradiol undecylate in men may include breast tenderness, breast development, feminization, sexual dysfunction, infertility, fluid retention, and cardiovascular issues. Estradiol undecylate is a synthetic estrogen and hence is an agonist of the estrogen receptor, the biological target of estrogens like estradiol. It is an estrogen ester and a very long-lasting prodrug of estradiol in the body. Because of this, it is considered to be a natural and bioidentical form of estrogen. An injection of estradiol undecylate has a duration of about 1 to 4 months.
Estradiol undecylate was first described in 1953 and was introduced for medical use by 1956. It has been used in Europe as a parenteral estrogen to treat prostate cancer in men, although not as often as polyestradiol phosphate.
Estradiol undecylate has been used as a form of high-dose estrogen therapy to treat prostate cancer, but has since largely been superseded for this indication by newer agents with fewer adverse effects (e.g., gynecomastia and cardiovascular complications) like GnRH analogues and nonsteroidal antiandrogens. It has been assessed for this purpose in a number of clinical studies. It has been used at a dosage of 100 mg every 3 to 4 weeks (or once a month) by intramuscular injection for this indication.
Estradiol undecylate has also been used to treat breast cancer in women. It has been used in menopausal hormone therapy as well, for instance in the treatment of hot flashes and other menopausal symptoms. Along with estradiol valerate, estradiol cypionate, and estradiol benzoate, estradiol undecylate has been used as an intramuscular estrogen in feminizing hormone therapy for transgender women. It has been used at doses of 100 to as much as 800 mg per month by intramuscular injection for this purpose.
|Oral||Estradiol||1–2 mg 3x/day|
|Conjugated estrogens||1.25–2.5 mg 3x/day|
|Ethinylestradiol sulfonate||1–2 mg 1x/week|
|Fosfestrol||100–480 mg 1–3x/day|
|Estramustine phosphate||140–1400 mg/day|
|Transdermal patch||Estradiol||2–6x 100 μg/day|
Scrotal: 1x 100 μg/day
|IM or SC injection||Estradiol benzoate||1.66 mg 3x/week|
|Estradiol dipropionate||5 mg 1x/week|
|Estradiol valerate||10–40 mg 1x/1–2 weeks|
|Estradiol undecylate||100 mg 1x/4 weeks|
|Polyestradiol phosphate||Alone: 160–320 mg 1x/4 weeks|
With oral EE: 40–80 mg 1x/4 weeks
|Estrone||2–4 mg 2–3x/week|
|IV injection||Fosfestrol||300–1200 mg 1–7x/week|
|Estramustine phosphate||240–450 mg/day|
|Note: Dosages are not necessarily equivalent. Sources: See template.|
|Route||Ingredient||Form||Dose||Major brand names|
|Oral||Estradiol||Tablet||0.1, 0.2, 0.5, 1, 2, or 4 mg per tablet||Estrace, Ovocyclin|
|Estradiol acetatea||Tablet||0.45, 0.9, or 1.8 mg per tablet||Femtrace|
|Estradiol valerate||Tablet||0.5, 1, 2, or 4 mg per tablet||Progynova|
|Mucosalb||Estradiola||Tablet||0.125, 0.25, or 1.0 mg per tablet||Diogynets, Estradiol Membrettes|
|Intranasal||Estradiola||Nasal spray||150 µg per spray (60 sprays per bottle)||Aerodiol|
|Transdermal||Estradiol||Patch||14, 25, 37.5, 50, 60, 75, or 100 µg E2 per day for 3–4 or 7 days||Climara, Estraderm, Vivelle|
|Gel dispenser||0.06% (0.87 or 1.25 g gel or 0.52 or 0.75 mg E2 per activation)||Elestrin, EstroGel|
|Gel packet||0.1% (0.25, 0.5, or 1.0 g gel or 2.5, 5, or 10 mg E2 per packet)||DiviGel, Sandrena|
|Emulsion||0.14% (1.74 g emulsion or 4.35 mg E2 per pouch; 50 µg/day E2)||Estrasorb|
|Spray||1.53 mg per spray||Evamist|
|Vaginal||Estradiol||Tablet||10 or 25 µg per tablet||Vagifem|
|Cream||0.01% (0.1 mg E2 per 1.0 g cream)||Estrace|
|Suppositorya||4 or 40 μg per suppository||Ovocyclin|
|Insert||4 or 10 µg per insert (daily for 2 weeks then twice weekly)||Imvexxy|
|Ring||2 mg per ring (7.5 µg/day E2 for 3 months)||Estring|
|Estradiol acetate||Ring||12.4 or 24.8 mg per ring (50 or 100 µg/day E2 for 3 months)||Femring|
|Injection (IM or SC)||Estradiol||Microspheres||1 mg/mL||Juvenum E|
|Estradiol benzoate||Oil solution||0.167, 0.2, 0.333, 1, 1.67, 2, 5, 10, 20, or 25 mg/mL||Progynon-B|
|Aqueous suspensiona||5 mg/mL||Agofollin Depot|
|Estradiol cypionate||Oil solution||1, 3, or 5 mg/mL||Depo-Estradiol|
|Aqueous suspension||5 mg/0.5 mL (available only with a progestin)||Cyclofem, Lunelle|
|Estradiol dipropionatea||Oil solution||0.1, 0.2, 0.5, 1, 2.5, or 5 mg/mL||Di-Ovocylin, Progynon-DP|
|Estradiol enantate||Oil solution||5 or 10 mg/mL (available only with a progestin)||Perlutal, Topasel|
|Estradiol undecylatea||Oil solution||100 mg/mL||Delestrec, Progynon Depot 100|
|Estradiol valerate||Oil solution||5, 10, 20, or 40 mg/mL||Delestrogen, Progynon Depot|
|Polyestradiol phosphatea||Aqueous solution||40 or 80 mg per vial/ampoule||Estradurin|
|Implant||Estradiola||Pellet||20, 25, 50, or 100 mg per pellet (usually every 6 months)||Estradiol Implants, Meno-Implant|
|Abbreviations: E2 = Estradiol. Footnotes: a = Discontinued or mostly discontinued. b = Buccal or sublingual. Notes: (1): This table mostly does not include combination products, for instance estradiol formulated in combination with a progestogen or androgen. (2): This table does not include compounded estradiol products; only approved pharmaceutical preparations are included. (3): The availability of pharmaceutical estradiol products differs by country (see Estradiol (medication) § Availability). (4): Some of these formulations and doses have been marketed previously but may no longer be available. Sources: See template.|
Contraindications of estrogens include coagulation problems, cardiovascular diseases, liver disease, and certain hormone-sensitive cancers such as breast cancer and endometrial cancer, among others.
Estradiol undecylate and its side effects have been evaluated for the treatment of advanced prostate cancer in a phase III international multicenter randomized controlled trial headed by Jacobi and colleagues of the Department of Urology, University of Mainz. The study consisted of 191 patients from 12 treatment centers, who were treated for 6 months with intramuscular injections of either 100 mg/month estradiol undecylate (96 men) or 300 mg/week cyproterone acetate (95 men). Findings for a subgroup of 42 men at the University of Mainz center were initially reported in 1978 and 1980. These men were age 51 to 84 years (mean 68 years), and men with pre-existing cardiovascular disease were excluded. A considerable incidence of cardiovascular complications was reported for the estradiol undecylate group (76%; 16/21 incidence total); there was a 67% (14/21) incidence of cardiovascular morbidity and a 9.5% (2/21) incidence of cardiovascular mortality. The cardiovascular morbidity in this group included peripheral edema and superficial thrombophlebitis (38%; 8/21), coronary heart disease (24%; 5/21), and a deep vein thrombosis (4.8%; 1/21), while the cardiovascular mortality included a myocardial infarction (4.8%; 1/21) and a pulmonary embolism (4.8%; 1/21). Eight of the cases of cardiovascular complications in the estradiol undecylate group, including the two deaths, were regarded as "severe". Conversely, no incidence of cardiovascular toxicity occurred in the cyproterone acetate comparison group (0%; 0/21). Other side effects of estradiol undecylate included gynecomastia (100%; 21/21) and erectile dysfunction (90%; 19/21). The cardiovascular complications with estradiol undecylate in this relatively small study are in contrast to large and high-quality clinical studies of high-dose polyestradiol phosphate and transdermal estradiol for prostate cancer, in which minimal to no cardiovascular toxicity has been observed.
An expanded report of 191 patients, which included the 42 patients from the University of Mainz center plus an additional 149 patients from 11 other centers, was published in 1982. The antitumor effectiveness of estradiol undecylate and cyproterone acetate in this study was equivalent. The rates of improvement, no response, and deterioration were 52%, 41%, and 7% in the estradiol undecylate group and 48%, 44%, and 8% in the cyproterone acetate group, respectively. However, the incidence of a selection of specific side effects, including gynecomastia, breast tenderness, edema, and thrombosis, was significantly lower in the cyproterone acetate group than in the estradiol undecylate group (37% vs. 94%, respectively). Gynecomastia specifically occurred in 13% (12/96) of the patients in the cyproterone acetate group and 77% (73/95) of the patients in the estradiol undecylate group. Erectile dysfunction occurred in "essentially all" patients in both groups. Leg edema occurred in 18% (17/95) of the estradiol undecylate group and 4.2% (4/96) of the cyproterone acetate group, while the incidences of superficial thrombophlebitis and coronary heart disease both were not described. The incidence of thrombosis was 4.2% (4/95) in the estradiol undecylate group and 5.3% (5/96) in the cyproterone acetate group. There were five deaths in total, three in the estradiol undecylate group and two in the cyproterone acetate group. Two of the deaths in each of the treatment groups were due to cardiovascular events, while the remaining death in the estradiol undecylate group was due to unknown causes. The similar rate of cardiovascular complications besides edema between estradiol undecylate and cyproterone acetate that was observed is in contrast to the initial 42-patient report and to findings with other estrogens, such as diethylstilbestrol and estramustine phosphate, which have been shown to possess significantly higher cardiovascular toxicity than cyproterone acetate. On the basis of the expanded study, the researchers concluded that cyproterone acetate was an "acceptable alternative" to estrogen therapy with estradiol undecylate, but with a "considerably more favorable" side-effect profile.
After the completion of the initial expanded study, a 5-year extension trial primarily of the Ruhr University Bochum center subgroup, led by Tunn and colleagues, was conducted. In this study, the cyproterone acetate group was changed from intramuscular injections to 100 mg/day oral cyproterone acetate. Of the 39 patients in the study, the global 5-year survival rate was not significantly different between the estradiol undecylate and cyproterone acetate groups (24% and 26%, respectively). In patients without metastases, the 5-year survival rate was 51% in the cyproterone acetate group relative to 43% in the estradiol undecylate group, although the difference was not statistically significant. In terms of non-prostate cancer deaths, there were 5 in the CPA group and 6 in the EU group. The incidence of cardiovascular-related mortality was 3 deaths in the CPA group and 3 deaths in the EU group.
Side effects during therapy with massive doses of estradiol undecylate in women with advanced breast cancer have included appetite loss, nausea, vomiting, vaginal bleeding, vaginal discharge, nipple pigmentation, breast pain, rash, urinary incontinence, edema, drowsiness, hypercalcemia, and local injection-site reactions. Like other estrogens, estradiol undecylate has been found to produce testicular abnormalities and disturbances of spermatogenesis in men.
|Side effect||Estradiol undecylate
100 mg/month i.m. (n = 96)
100 mg/day oral (n = 95)
"Occurred in essentially all patients of both groups"
|Notes: For 6 months in 191 men age 51 to 88 years with prostate cancer. Footnotes: * = Differences in incidences between groups were statistically significant. a = Due to unknown causes. Sources: See template.|
Estradiol undecylate has been used clinically at massive doses of as much as 800 to 2,400 mg per month by intramuscular injection, given in divided doses of 100 to 200 mg per injection two to three times per week. For purposes of comparison, a single 100 mg intramuscular injection of estradiol undecylate has been found to produce maximal estradiol levels of about 500 pg/mL. Symptoms of estrogen overdosage may include nausea, vomiting, bloating, increased weight, water retention, breast tenderness, vaginal discharge, heavy legs, and leg cramps. These side effects can be diminished by reducing the estrogen dosage.
Esters of estradiol like estradiol undecylate are readily hydrolyzed prodrugs of estradiol, but have an extended duration when administered in oil via intramuscular injection due to a depot effect afforded by their fatty acid ester moiety. As prodrugs of estradiol, estradiol undecylate and other estradiol esters are estrogens. Estradiol undecylate is of about 62% higher molecular weight than estradiol due to the presence of its C17β undecylate ester. Because estradiol undecylate is a prodrug of estradiol, it is considered to be a natural and bioidentical form of estrogen.
The effects of estradiol undecylate on cortisol, dehydroepiandrosterone sulfate, testosterone, and prolactin levels as well as on the hypothalamic–pituitary–adrenal axis have been studied in men with prostate cancer and compared with those of high-dose cyproterone acetate therapy. The effects of estradiol undecylate on serum lipids and ceruloplasmin levels have been studied as well.
|Estrogen||Form||Major brand name(s)||EPD (14 days)||CIC-D (month)||Duration|
|Estradiol||Oil solution||–||40–60 mg||–||1–10 mg ≈ 1–2 days|
|Aqueous suspensiona||Mego-E||?||3.5 mg||3.5 mg ≈ >5 days|
|Microspheres||Juvenum-E, Juvenum||?||–||1 mg ≈ 30 days|
|Estradiol benzoate||Oil solution||Progynon-B||25–35 mg||–||5 mg ≈ 3–6 days|
|Aqueous suspension||Agofollin-Depot||20 mg||–||10 mg ≈ 16–21 days|
|Estradiol dipropionate||Oil solution||Agofollin, Di-Ovocyclin, Progynon DP||25–30 mg||–||5 mg ≈ 5–8 days|
|Estradiol valerate||Oil solution||Delestrogen, Progynon Depot, Mesigyna||20–30 mg||5 mg||5 mg ≈ 7–8 days; 10 mg ≈ 10–14 days;|
40 mg ≈ 14–21 days; 100 mg ≈ 21–28 days
|Estradiol cypionate||Oil solution||Depo-Estradiol, Depofemin||20–30 mg||–||5 mg ≈ 11–14 days|
|Aqueous suspensiona||Cyclofem, Lunelle||?||5 mg||5 mg ≈ 14–24 days|
|Estradiol benzoate butyratea||Oil solution||Redimen, Soluna, Unijab||?||10 mg||10 mg ≈ 21 days|
|Estradiol enanthatea||Oil solution||Perlutal, Topasel, Yectames||?||5–10 mg||10 mg ≈ 20–30 days|
|Estradiol undecylate||Oil solution||Delestrec, Progynon Depot 100||?||–||10–20 mg ≈ 40–60 days; 25–50 mg ≈ 60–120 days|
|Polyestradiol phosphate||Aqueous solution||Estradurin||40–60 mg||–||40–50 mg ≈ 30 days; 320 mg = >84 daysb|
|Estrone||Oil solution||Kestrin, Theelin||?||–||1–2 mg ≈ 2–3 days|
|Aqueous suspension||Estrone Aqueous Suspension||?||–||?|
|Estriol||Oil solution||–||?||–||1–2 mg ≈ 1–4 days|
|Polyestriol phosphate||Aqueous solution||Gynäsan, Klimadurin, Triodurin||?||–||50 mg ≈ 30 days; 80 mg ≈ 60 days|
|Notes: All by intramuscular injection. The vaginal epithelium maturation dosage of estradiol benzoate or estradiol valerate is 5 to 7 mg/week. An effective ovulation-inhibiting dose of estradiol undecylate is 20–30 mg/month. Estradiol production during the menstrual cycle is 30–640 µg/day (6.4–8.6 mg total per month or cycle). Footnotes: a = Available only in combined injectable contraceptives (i.e., not available alone). b = The elimination half-life of polyestradiol phosphate after a single injection of 320 mg is 70 days. Sources: See template.|
A phase III clinical trial comparing high-dose intramuscular cyproterone acetate (300 mg/week) and high-dose intramuscular estradiol undecylate (100 mg/month) in the treatment of prostate cancer found that estradiol undecylate suppressed testosterone levels into the castrate range (< 50 ng/dL) within at least 3 months whereas testosterone levels with cyproterone acetate were significantly higher and above the castrate range even after 6 months of treatment. With estradiol undecylate, testosterone levels fell from 416 ng/dL to 38 ng/mL (-91%) after 3 months and to 29.6 ng/dL (-93%) after 6 months, whereas with cyproterone acetate, testosterone levels fell from 434 ng/dL to 107 ng/mL (-75%) at 3 months and to 102 ng/mL (-76%) at 6 months. In another study using the same dosages, estradiol undecylate suppressed testosterone levels by 97% while CPA suppressed them by 70%. In accordance, whereas estrogens are well-established as able to suppress testosterone levels into the castrate range at sufficiently high dosages, progestogens like cyproterone acetate on their own are able to decrease testosterone levels only up to an apparent maximum of around 70 to 80%.
The long-term effects of estradiol undecylate on testicular morphology in transgender women have been studied.
The pharmacokinetics of estradiol undecylate have been assessed in a few studies. Following a single intramuscular injection of 100 mg estradiol undecylate in oil, mean levels of estradiol were about 500 pg/mL a day after injection and about 340 pg/mL 14 days after injection. Levels of estradiol with intramuscular estradiol undecylate were reported to be very irregular and to vary by as much as 10-fold between individuals. In another study, following a single intramuscular injection of 32.2 mg estradiol undecylate, levels of estradiol peaked at around 400 pg/mL after 3 days and decreased from this peak to around 200 pg/mL after 6 days. In a continuous administration study of 100 mg/month estradiol undecylate, estradiol levels were about 560 pg/mL at 3 months and about 540 pg/mL at 6 months of therapy. Due to its more protracted duration, doses of estradiol undecylate that are typical of other estradiol esters produce only "subthreshold" estradiol levels, and for this reason, higher single doses of estradiol undecylate are necessary for similar effects. However, the relatively low levels of estradiol produced by lower doses of estradiol undecylate are favorable for menopausal replacement therapy.
The duration of estradiol undecylate is markedly prolonged relative to that of estradiol benzoate, estradiol valerate, and many other estradiol esters. A single intramuscular injection of 10 to 12.5 mg estradiol undecylate has a duration of 40 to 60 days (~1–2 months) and of 25 to 50 mg estradiol undecylate has an estimated duration of effect of 2 to 4 months in postmenopausal women. A single intramuscular injection of 20 to 30 mg estradiol undecylate has been found to inhibit ovulation when used as an estrogen-only injectable contraceptive in premenopausal women for 1 to 3 months (mean 1.7 months) as well. When used at a higher dose of 100 mg per injection in men with prostate cancer, estradiol undecylate has been given usually once a month. After a single subcutaneous injection of estradiol undecylate in rats, its duration of effect was 80 days (about 2.5 months). Due to its very prolonged duration, estradiol undecylate has been described in general as a favorable alternative to estradiol implants.
Estradiol undecylate has not been used via oral administration. However, a closely related estradiol ester, estradiol decanoate (estradiol decylate), has been studied via the oral route, and has been found to possess significant oral bioavailability, to produce relatively high estradiol levels of about 100 pg/mL after a single 0.5 mg oral dose and about 100 to 150 pg/mL with continuous 0.25 mg/day oral therapy, and to have a much higher estradiol-to-estrone ratio than oral estradiol of about 2:1. It is thought that this is due to absorption of estradiol decanoate by the lymphatic system and a consequent partial bypass of first-pass metabolism in the liver and intestines, which is similarly known to occur with oral testosterone undecanoate.
Estradiol levels after an intravenous injection of 20 mg estradiol or an intramuscular injection of equimolar doses of different estradiol esters in oil in 3 postmenopausal women each. Assays were performed using radioimmunoassay with chromatographic separation. Source was Leyendecker et al. (1975).
Estradiol undecylate is a synthetic estrane steroid and an estradiol ester. It is specifically the C17β undecylate (undecanoate) ester of estradiol. The compound is also known as estradiol 17β-undecylate or as estra-1,3,5(10)-triene-3,17β-diol 17β-undecanoate. The undecylic acid (undecanoic acid) ester of estradiol undecylate is a medium-chain fatty acid and is found naturally in many foods, some examples of which include coconut, fruits, fats, oils, and rice.
Estradiol undecylate is a relatively long-chain ester of estradiol. Its undecylate ester contains 11 carbon atoms. For comparison, the ester chains of estradiol acetate, estradiol valerate, and estradiol enantate have 2, 5, and 7 carbon atoms, respectively. As a result of its longer ester chain, estradiol undecylate is the most lipophilic of these estradiol esters, and for this reason, it has by far the longest duration when administered in oil solution by intramuscular injection.
A few estradiol esters related to estradiol undecylate include estradiol decanoate, estradiol diundecylate, and estradiol diundecylenate. Estradiol undecylate shares the same undecylate ester as testosterone undecanoate, an androgen/anabolic steroid and very long-lasting testosterone ester.
|Estradiol acetate||C3||Ethanoic acid||Straight-chain fatty acid||2||1.15||0.87||2.8–3.9|
|Estradiol benzoate||C3||Benzenecarboxylic acid||Aromatic fatty acid||– (~4–5)||1.38||0.72||4.5–5.7|
|Estradiol dipropionate||C3, C17β||Propanoic acid (×2)||Straight-chain fatty acid||3 (×2)||1.41||0.71||4.3|
|Estradiol valerate||C17β||Pentanoic acid||Straight-chain fatty acid||5||1.31||0.76||5.8–6.0|
|Estradiol cypionate||C17β||Cyclopentylpropanoic acid||Aromatic fatty acid||– (~6)||1.46||0.69||6.5–7.1|
|Estradiol benzoate butyrate||C3, C17β||Benzoic acid, butyric acid||Mixed fatty acid||– (~6, 2)||1.64||0.61||5.9|
|Estradiol enantate||C17β||Heptanoic acid||Straight-chain fatty acid||7||1.41||0.71||7.0|
|Estradiol dienantate||C3, C17β||Heptanoic acid (×2)||Straight-chain fatty acid||7 (×2)||1.82||0.55||8.1–9.1|
|Estradiol undecylate||C17β||Undecanoic acid||Straight-chain fatty acid||11||1.62||0.62||9.2|
|Estradiol stearate||C17β||Octadecanoic acid||Straight-chain fatty acid||18||1.98||0.51||12.2|
|Estradiol distearate||C3, C17β||Octadecanoic acid (×2)||Straight-chain fatty acid||18 (×2)||2.96||0.34||20.2|
|Estradiol sulfate||C3||Sulfuric acid||Non-fatty acid||–||1.29||0.77||0.3–3.8|
|Estradiol glucuronide||C17β||Glucuronic acid||Non-fatty acid||–||1.65||0.61||2.1–2.7|
|Estramustine phosphated||C3, C17β||Normustine, phosphoric acid||Non-fatty acid||–||1.91||0.52||2.9–5.0|
|Polyestradiol phosphatee||C3–C17β||Phosphoric acid||Non-fatty acid||–||1.23f||0.81f||2.9g|
|Footnotes: a = Length of ester in carbon atoms for straight-chain fatty acids or approximate length of ester in carbon atoms for aromatic fatty acids. b = Relative estradiol content by weight (i.e., relative estrogenic potency). c = Experimental or predicted octanol/water partition coefficient (i.e., lipophilicity/hydrophobicity). Retrieved from PubChem and DrugBank. d = Also known as estradiol normustine phosphate. e = Polymer of estradiol phosphate (~13 repeat units). f = Relative molecular weight or estradiol content per repeat unit. g = logP of repeat unit (i.e., estradiol phosphate). Sources: See individual articles.|
Estradiol undecylate was first described in the scientific literature, along with estradiol valerate and a variety of other estradiol esters, by Karl Junkmann of Schering AG in 1953. It was introduced for medical use via intramuscular injection by 1956. Syntex applied for a patent for estradiol undecylate in 1958, which was granted in 1961 and was given a priority date of 1957. Estradiol undecylate was introduced for medical use and was employed for decades, but was eventually discontinued. It remained in use in some countries as late as the 2000s.
Harry Benjamin reported on the use of estradiol undecylate in transgender women in his book The Transsexual Phenomenon in 1966 and in a literature review in the Journal of Sex Research in 1967.
Estradiol undecylate is the generic name of the drug and its INN and USAN. It is also spelled in some publications as estradiol unducelate and is also known as estradiol undecanoate. In German, it is known under a variety of spellings including as estradiolundecylat, östradiolundecylat, östradiolundezylat, oestradiolundecylat, oestradiolundezylat, and others. Estradiol undecylate is known by its former developmental code names RS-1047 and SQ-9993 as well.
The major brand name of estradiol undecylate is Progynon Depot 100. It has also been marketed under other brand names including Delestrec, Depogin, Estrolent, Oestradiol D, Oestradiol-Retard Theramex, and Primogyn Depot [0,1 mg/ml], among others.
Estradiol undecylate was available in the Europe (including in France, Germany, Great Britain, Monaco, the Netherlands, Switzerland), and Japan. However, it has been discontinued and is no longer available.
Estradiol undecylate was studied by Schering alone as an estrogen-only injectable contraceptive at a dose of 20 to 30 mg once a month. It was effective, lacked breast and thromboembolic complications, lacked other side effects besides amenorrhea, and prevented ovulation for 1 to 3 months (mean 1.7 months) following a single dose. However, uterine growth of 1 to 2 cm was observed after one year, and endometrial hyperplasia was occasionally encountered. The preparation was not further developed as a form of birth control due to the risks of endometrial hyperplasia and cancer associated with long-term unopposed estrogen therapy.
Estradiol undecylate, in combination with norethisterone enantate (at doses of 5 to 10 mg and 50 to 70 mg, respectively), was studied by Schering as a combined injectable contraceptive and was found to be effective and well-tolerated, but ultimately was not marketed for this use.
Natural estrogens considered here include: [...] Esters of 17β-estradiol, such as estradiol valerate, estradiol benzoate and estradiol cypionate. Esterification aims at either better absorption after oral administration or a sustained release from the depot after intramuscular administration. During absorption, the esters are cleaved by endogenous esterases and the pharmacologically active 17β-estradiol is released; therefore, the esters are considered as natural estrogens.
Another preparation of even higher potency is Squibb's Delestrec, which at this writing is not yet on the market in the United States, but is well known in Germany and other European countries under the name of Progynon Depot (Schering). It is chemically Estradiol Undecylate in oil, likewise slowly absorbing, and containing 100 mg. to 1 cc. Injections of 1 cc. once or twice a month can be sufficient. Occasionally, however, larger doses are required to influence the patient's emotional distress.
Progynon-Depot ist eine Oestrogenpräparat mit einem Depoteffekt von 4-6 Wochen. 1 ml Progynon Depot 100 mg enthält 100 mg Oestra- diolundecylat in öliger Lösung. Oestradiolundecylat ist ein Ester des natürlichen Oestrogens Oestradiol.
As in the case of progestogens the esters of oestradiol vary in the duration of their effect. Oestradiol benzoate is short-acting (three days to a week). Oestradiol valerianate is somewhat longer-acting, and oestradiol enanthate and undecylate have considerably more prolonged duration of effectiveness. The undecylate may remain effective for some months, and should not be employed, [...]
Treatment of sexual offenders. Hormone therapy. [...] Oestrogens may cause breast hypertrophy, testicular atrophy, osteoporosis (oral ethinyl oestradiol 0.01-0.05 mg/day causes least nausea). Depot preparation: oestradiol [undecyleate] 50-100mg once every 3–4 weeks. Benperidol or butyrophenone and the antiandrogen cyproterone acetate also used.
Estradiol 17β, estradiol benzoate, estradiol valerianate, and estradiol undecylate were injected intravenously and intramuscularly to postmenopausal woman and to female castrates. Equal doses were used corresponding to 20 mg of free estradiol 17β. Estradiol 17β, estrone, FSH and LH were measured in serum by radioimmunoassay before and after application of the hormone and the estradiol esters. Thus the depot effect of the different esters could be compared.
Estradiol undecylenate has a more protracted effect but it releases only subthreshold doses of steroid (advantage may be taken of this for the treatment of menopause).