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.
Pharmacodynamics of estradiol
Lower dosages and concentrations of estradiol can also significantly suppress gonadotropin secretion and testosterone levels in men and transgender women. A retrospective study of oral estradiol monotherapy in transgender women found that dosages of 1 to 8 mg/day increased mean estradiol levels to about 50 to 150 pg/mL and suppressed mean testosterone levels to about 120 to 10 ng/dL. However, there was high interindividual variability in the estradiol and testosterone levels achieved, and testosterone levels were insufficiently suppressed in many even at 8 mg/day. In another study, a dosage of 1 mg/day oral micronized estradiol in healthy older men, which increased circulating estradiol levels by a relatively high amount of 6-fold (to 159 pg/mL), estrone levels by 15-fold (to 386 pg/mL), and SHBG levels by 17%, was found to suppress total testosterone levels by 27% (to 436 ng/dL) and free testosterone levels by 34% (to 11.8 ng/dL). A pharmacodynamic study of testosterone suppression by polyestradiol phosphate in men with prostate cancer found that estradiol levels of about 135 pg/mL (500 pmol/L) would decrease testosterone levels by 50% (from 430 ng/dL to 215 ng/dL), while estradiol levels of about 410 to 545 pg/mL (1500–2000 pmol/L) would decrease testosterone levels well into the castrate range to about 6 to 12 ng/dL (0.2–0.4 nmol/L).