<unk>  (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<unk>  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.<unk>  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.<unk>  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,<unk>  has a greatly increased terminal half-life relative to estradiol (6 hours vs. 2 minutes).<unk>  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<unk>  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.<unk>  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,<unk>  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.<unk>  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<unk> . 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 long-acting estradiol ester is estradiol undecylate, which has 11 carbon atoms instead of the 18 carbon atoms in<unk> .
Estradiol stearate
Estradiol undecylate
Estradiol furoate
Estradiol valerate
Estradiol hemisuccinate
Estradiol diundecylenate
Estradiol dienantate
Estradiol diundecylate