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)
A variety of analogues of estriol are known, including both naturally occurring isomers and synthetic substituted derivatives and esters. 16β-Epiestriol (epiestriol), 17α-epiestriol, and 16β,17α-epiestriol are isomers of estriol that are endogenous weak estrogens. Mytatrienediol (16α-methyl-16β-epiestriol 3-methyl ether) is a synthetic derivative of 16β-epiestriol that was never marketed. Estriol acetate benzoate, estriol succinate, and estriol tripropionate are synthetic estriol esters that have been marketed for medical use, whereas estriol dihexanoate, estriol dipropionate, and estriol triacetate have not been introduced. Quinestradol is the 3-cyclopentyl ether of estriol and has also been marketed. Polyestriol phosphate, an ester of estriol in the form of a polymer, has been marketed previously as well. These esters, ethers, and polymers are prodrugs of estriol. Ethinylestriol and nilestriol are synthetic C17α ethynylated derivatives of estriol. Ethinylestriol has not been marketed, but nilestriol, which is the 3-cyclopentyl ether of ethinylestriol and a prodrug of it, has been.