estradiol valerate, it has been reported that a dose of 5 mg has a duration of 7 to 8 days, 10 mg a duration of 10 to 14 days, 40 mg a duration of 2 to 3 weeks (14 to 21 days), and 100 mg a duration of 3 to 4 weeks (21 to 28 days). A study of pseudopregnancy with intramuscular injections of 40 mg/week estradiol valerate and 250 mg/week hydroxyprogesterone caproate in women with estrogen deficiency observed estradiol levels of about 3,100 pg/mL at 3 months of therapy and 2,500 pg/mL at 6 months of therapy. Subcutaneous injection Estradiol esters like estradiol valerate and estradiol cypionate can be given by subcutaneous injection instead of intramuscular injection. Intravenous injection The administration of estradiol valerate by intravenous injection has been studied. It has been found to be very rapidly cleaved into estradiol. The bioavailability and metabolism of estradiol valerate does not differ with intravenous versus intramuscular injection. Conversely, intravenous injection of estradiol valerate has a very short duration, whereas intramuscular injection has a long duration and elimination half-life. Chemistry Estradiol valerate is a synthetic estrane steroid and the C17β valerate (pentanoate) fatty acid ester of estradiol. It is also known as estradiol 17β-valerate or as estra-1,3,5(10)-triene-3,17β-diol 17β-pentanoate. Other common esters of estradiol in use include estradiol cypionate, estradiol enantate, and estradiol acetate, the former two of which are C17β esters of estradiol similarly to estradiol valerate and the latter of which is the C3 acetate ester of estradiol. The experimental log octanol/water partition coefficient (log P) of estradiol valerate is 5.6. History Estradiol valerate was patented by Ciba in 1940 and 1941, with a priority date of 1936. It was synthesized and studied, along with a variety of other estradiol esters, by Karl Junkmann of Schering AG in 1953. The medication was first introduced for medical use via intramuscular injection in 1954 by Schering in Europe under the brand name Progynon Depot and by Squibb in the United States under the brand name Delestrogen. In 1966, oral estradiol valerate was introduced by Schering for medical use in Europe under the brand name Progynova. A report of its metabolism was published in 1967. Esterification of estradiol, as in estradiol valerate, has been claimed to improve its metabolic stability with oral administration. In 1968, micronized preparations of oral estradiol valerate were first introduced under the brand names Progynova 21 and Progynova 21