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.
Estradiol-containing birth control pill
Combined birth control pills that contain natural estradiol or an estradiol ester (e.g., estradiol valerate) include:It is hypothesized that these contraceptives may pose less of a risk of blood clots than contraceptives containing ethinylestradiol, which is the conventional estrogen that is used in oral contraceptives, but this has yet to be proven. However, incidence of irregular vaginal bleeding may be higher with estradiol-containing contraceptives in relation to the fact that estradiol is a weaker estrogen than ethinylestradiol in the endometrium.