Estradiol enantate
Estradiol enantate, sold under the brand names Perlutal and Topasel among others, is an estrogen medication which is used in hormonal birth control. It is formulated in combination with dihydroxyprogesterone acetophenide (DHPA; algestone acetophenide), a progestin, and is used as a combined injectable contraceptive. Estradiol enantate is not available alone. The medication is given by injection into muscle once a month.
Side effects of estradiol enantate include breast tenderness, breast enlargement, nausea, headache, and fluid retention. The drug is a synthetic estrogen and hence is an agonist of the estrogen receptor (ER), the biological target of estrogens like estradiol. Estradiol enantate is an estrogen ester and a long-lasting prodrug of estradiol in the body. Because of this, it is considered to be a natural and bioidentical form of estrogen.
Estradiol enantate was first described by 1954, and was first studied in combination with DHPA as a combined injectable contraceptive in 1964. The combination was introduced for clinical use by the mid-1970s. Estradiol enantate is not available as a standalone medication (i.e., by itself without DHPA). The combination is available in Latin America and Hong Kong, and was also previously marketed in Spain and Portugal.
Estetrol (medication)
Estetrol is metabolized slowly and minimally, and is not transformed into other estrogens such as estradiol, estrone, or estriol. This is related to the fact that estetrol is already an end-stage product of phase I estrogen metabolism in humans. The medication is conjugated via glucuronidation and to a lesser extent via sulfation. The biological half-life of estetrol is about 28 hours, with a range of 18 to 60 hours. The blood half-lives of estradiol and estriol, at about 1 to 2 hours and 20 minutes, respectively, are far shorter than that of estetrol, whereas the biological half-life of ethinylestradiol, at approximately 20 hours, is more similar to that of estetrol. Enterohepatic recirculation may occur with estetrol, similarly to other steroidal estrogens, although it has also been reported that estetrol does not seem to enter the enterohepatic circulation. Estetrol is excreted mostly or completely in urine, virtually entirely in the form of conjugates (unconjugated accounting for 0.2–0.7%). In one study, a median of 79.7% (range 61.1–99.0%) was recovered from urine; this was primarily as estetrol glucuronide (median 60.7%, range 47.6–77.2%), and, to a lesser extent, as estetrol sulfate (median 17.6%, range 13.2–22.1%).