Estradiol 17-Valerate

Estradiol valerate (EV, E2V) (INN, USAN, JAN) (brand names Altadiol, Deladiol, Delestrogen, Estraval, Lastrogen, Progynova, Valergen, many others), or oestradiol valerate (BAN), is a synthetic ester, specifically the 17-pentanoyl ester, of the natural estrogen, 17β-estradiol. It was first introduced, as Delestrogen by Squibb in the United States, in 1954, and along with estradiol benzoate (1936) and estradiol cypionate (1952), has since become one of the most widely used esters of estradiol.
Upon ingestion, regardless of the route of administration, estradiol valerate behaves as a prodrug, being cleaved by esterases in blood plasma and the liver into 17β-estradiol and valeric acid. However, compared to estradiol itself, estradiol valerate is absorbed more slowly and possesses a longer duration, especially when given in an oil solution via intramuscular injection (in which it acts as a depot). As a result, it can be administered less frequently.
A single intramuscular injection of 4mg estradiol valerate results in maximal plasma levels of estradiol of about 390 pg/mL within three days of administration, with levels declining to 100 pg/mL by 12–13 days. A study of high-dose combined administration of 40mg estradiol valerate and 250mg hydroxyprogesterone caproate in women once weekly for six months (described as a "pseudopregnancy" regimen) found that serum levels of estradiol increased from 27.8–34.8 pg/mL to 3028–3226 pg/mL after three months and to 2491–2552 pg/mL after six months of treatment.