Estradiol (medication)
Estradiol is also widely available in combination with progestogens. It is available in combination with norethisterone acetate under the major brand names Activelle, Cliane, Estalis, Eviana, Evorel Conti, Evorel Sequi, Kliogest, Novofem, Sequidot, and Trisequens; with drospirenone as Angeliq; with dydrogesterone as Femoston, Femoston Conti; and with nomegestrol acetate as Zoely. Estradiol valerate is available with cyproterone acetate as Climen; with dienogest as Climodien and Qlaira; with norgestrel as Cyclo-Progynova and Progyluton; with levonorgestrel as Klimonorm; with medroxyprogesterone acetate as Divina and Indivina; and with norethisterone enantate as Mesigyna and Mesygest. Estradiol cypionate is available with medroxyprogesterone acetate as Cyclo-Provera, Cyclofem, Feminena, Lunelle, and Novafem; estradiol enantate with algestone acetophenide as Deladroxate and Topasel; and estradiol benzoate is marketed with progesterone as Mestrolar and Nomestrol.
Pharmacokinetics of estradiol
In contrast to estradiol, estrone has very low activity as an estrogen. The affinities of estrone for the human ERs and its estrogenic activity have been reported to be approximately 3 to 4% of those of estradiol. In addition, unlike estradiol and estriol, estrone is not accumulated in target tissues. Because estrone can be transformed into estradiol, most of its activity "in vivo" is actually due to conversion into estradiol. In accordance, dosages of oral and transdermal estradiol that achieve similar levels of estradiol have been found, in spite of markedly elevated levels of estrone with oral estradiol but not with transdermal estradiol, to possess equivalent and non-significantly different potency in terms of clinical measures including suppression of LH and FSH levels, inhibition of bone resorption, and relief of menopausal symptoms such as hot flashes. In addition, estradiol levels were found to correlate with these effects, while estrone levels did not. These findings suggest that estrone contributes very little or not at all to the estrogenic potency of estradiol, while also not antagonizing the estrogenic activity of estradiol. This contradicts some "in vitro" research suggesting that estrone might be able to partially antagonize the actions of estradiol.