Estradiol stearate

Estradiol stearate

Clinical data
Trade names	Depofollan
Other names	E2-17-St; Estradiol octadecanoate; Estradiol 17β-stearate; Estradiol 17β-octadecanoate
Routes of administration	Intramuscular injection
Drug class	Estrogen; Estrogen ester
Identifiers
IUPAC name [(8R,9S,13S,14S,17S)-3-Hydroxy-13-methyl-6,7,8,9,11,12,14,15,16,17-decahydrocyclopenta[a]phenanthren-17-yl] octadecanoate
CAS Number	82205-00-3 Y
PubChem CID	67100
ChemSpider	60448
UNII	59G2KR8QBG
CompTox Dashboard (EPA)	DTXSID401002548
Chemical and physical data
Formula	C36H58O3
Molar mass	538.857 g·mol−1
3D model (JSmol)	Interactive image
SMILES CCCCCCCCCCCCCCCCCC(=O)O[C@H]1CC[C@H]2[C@@H]3CCc4cc(O)ccc4[C@H]3CC[C@]12C
InChI InChI=1S/C36H58O3/c1-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18-35(38)39-34-24-23-33-32-21-19-28-27-29(37)20-22-30(28)31(32)25-26-36(33,34)2/h20,22,27,31-34,37H,3-19,21,23-26H2,1-2H3/t31-,32-,33+,34+,36+/m1/s1 Key:KIADYVOYCQRXRE-IMTRJTTHSA-N

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 stearate has a prolonged duration of action relative to estradiol regardless of whether it is given by intravenous injection or subcutaneous injection. This is in contrast to short-chain fatty acid esters of estradiol, such as estradiol benzoate, which do not show a prolonged duration with intravenous injection. When administered by intravenous injection in rodents, estradiol stearate has a greatly increased terminal half-life relative to estradiol (6 hours vs. 2 minutes). Estradiol stearate also had a half-life that was 60% longer than that of estradiol arachidonate, despite similar ester chain lengths. In contrast to the long-chain esters, the half-lives of short-chain estradiol esters such as estradiol acetate and estradiol hexanoate were the same as that of estradiol. As such, whereas short-chain estradiol esters are rapidly hydrolyzed, long-chain estradiol esters like estradiol stearate are resistant to metabolism. Thus, the prolongation of effect of short-chain estradiol esters is purely due to their increased lipophilicity and slow release from the injected depot, whereas the prolonged duration of long-chain estradiol esters is due both to this property and to their resistance to metabolism. Estradiol stearate is susceptible to first-pass metabolism in the liver, and hence has much greater potency by subcutaneous injection than by oral administration.

In addition to its endogenous role, estradiol stearate was previously available as a pharmaceutical drug for use via depot intramuscular injection. The medication was introduced between 1938 and 1941 under the brand name Depofollan. It has been used to treat prostate cancer. Estradiol stearate is a long-acting estrogen and is said to have been the first long-acting estrogen used in medicine, although it was never widely employed. It was reported to have a duration of more than one month. The medication was provided as an oil solution in ampoules containing 15 mg estradiol stearate. It was manufactured by Chinoin, a Hungarian pharmaceutical company. The compound was studied by Karl Miescher in 1938 and was patented by Miescher and Chinoin in 1939 and 1941, respectively. A similar clinically used long-acting estradiol ester is estradiol undecylate, which has 11 carbon atoms instead of the 18 carbon atoms in estradiol stearate.

• v
• t
• e

Structural properties of selected estradiol esters

Estrogen	Structure	Ester(s)				Relative mol. weight	Relative E2 contentb	log Pc
		Position(s)	Moiet(ies)	Type	Lengtha
Estradiol		–	–	–	–	1.00	1.00	4.0
Estradiol acetate		C3	Ethanoic acid	Straight-chain fatty acid	2	1.15	0.87	4.2
Estradiol benzoate		C3	Benzenecarboxylic acid	Aromatic fatty acid	– (~4–5)	1.38	0.72	4.7
Estradiol dipropionate		C3, C17β	Propanoic acid (×2)	Straight-chain fatty acid	3 (×2)	1.41	0.71	4.9
Estradiol valerate		C17β	Pentanoic acid	Straight-chain fatty acid	5	1.31	0.76	5.6–6.3
Estradiol benzoate butyrate		C3, C17β	Benzoic acid, butyric acid	Mixed fatty acid	– (~6, 2)	1.64	0.61	6.3
Estradiol cypionate		C17β	Cyclopentylpropanoic acid	Aromatic fatty acid	– (~6)	1.46	0.69	6.9
Estradiol enanthate		C17β	Heptanoic acid	Straight-chain fatty acid	7	1.41	0.71	6.7–7.3
Estradiol dienanthate		C3, C17β	Heptanoic acid (×2)	Straight-chain fatty acid	7 (×2)	1.82	0.55	8.1–10.4
Estradiol undecylate		C17β	Undecanoic acid	Straight-chain fatty acid	11	1.62	0.62	9.2–9.8
Estradiol stearate		C17β	Octadecanoic acid	Straight-chain fatty acid	18	1.98	0.51	12.2–12.4
Estradiol distearate		C3, C17β	Octadecanoic acid (×2)	Straight-chain fatty acid	18 (×2)	2.96	0.34	20.2
Estradiol sulfate		C3	Sulfuric acid	Water-soluble conjugate	–	1.29	0.77	0.3–3.8
Estradiol glucuronide		C17β	Glucuronic acid	Water-soluble conjugate	–	1.65	0.61	2.1–2.7
Estramustine phosphated		C3, C17β	Normustine, phosphoric acid	Water-soluble conjugate	–	1.91	0.52	2.9–5.0
Polyestradiol phosphatee		C3–C17β	Phosphoric acid	Water-soluble conjugate	–	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 exposure). c = Experimental or predicted octanol/water partition coefficient (i.e., lipophilicity/hydrophobicity). Retrieved from PubChem, ChemSpider, 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 = log P of repeat unit (i.e., estradiol phosphate). Sources: See individual articles.

See also

• List of estrogen esters § Estradiol esters