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.
Pharmacokinetics of progesterone
Progesterone does not appear to be available pharmaceutically in the form of subcutaneous pellet implants. This is in contrast to estradiol and testosterone. Progesterone may be available in the form of subcutaneous pellet implants from some compounding pharmacies however. Such products are not regulated for quality or effectiveness however. Subcutaneous implantation of progesterone has been studied in animals. Although progesterone is not available for subcutaneous implantation as a pharmaceutical product, subcutaneous implants of progestins, such as etonogestrel (Implanon/Nexplanon) and levonorgestrel (Jadelle/Norplant), are available as pharmaceutical preparations. They are used specifically as a form of long-lasting hormonal birth control.