Estradiol (medication)
Estradiol is available in a variety of different formulations, including oral, intranasal, transdermal/topical, vaginal, injectable, and implantable preparations. An ester may be attached to one or both of the hydroxyl groups of estradiol to improve its oral bioavailability and/or duration of action with injection. Such modifications give rise to forms such as estradiol acetate (oral and vaginal), estradiol valerate (oral and injectable), estradiol cypionate (injectable), estradiol benzoate (injectable), estradiol undecylate (injectable), and polyestradiol phosphate (injectable; a polymerized ester of estradiol), which are all prodrugs of estradiol.
Estriol (medication)
Following its discovery in 1930, estriol was introduced for medical use as an oral tablet in the 1930s. Emmenin and Progynon were oral estrogens that contained estriol conjugates, primarily estriol glucuronide, and were introduced in the 1930s. They were the first orally active estrogen preparations to be introduced in medicine. Estriol continues to be used medically today, widely throughout the world and in a variety of different formulations and brand names.