Estradiol (medication)
, estradiol is available in the United States in the following forms:Oral estradiol valerate (Progynova) and other esters of estradiol that are used by injection like estradiol benzoate, estradiol enantate, and estradiol undecylate all are not marketed in the U.S. Polyestradiol phosphate (Estradurin) was marketed in the U.S. previously but is no longer available.
Estriol (medication)
The bioavailability of estriol is markedly increased with vaginal administration compared to oral administration. The relative bioavailability of oral estriol was found to be about 10% of that of vaginal estriol. In accordance, a single dose of 8 mg oral estriol and of 0.5 mg vaginal estriol have been found to produce similar circulating concentrations of estriol. It has been said that 0.5 to 1 mg vaginal estriol may be equivalent in clinical effect to 8 to 12 mg oral estriol. The high bioavailability of vaginal estriol is due to rapid absorption and low metabolism in atrophic vaginal mucosa. Vaginal estriol at typical clinical dosages results both in high local concentrations of estriol in the vagina and in systemic action. Vaginal administration of low doses of 30 µg estriol and of higher doses of 0.5 and 1 mg estriol have been found to produce equivalent local effects in the vagina and improvement of vaginal symptoms, suggesting that a saturation of estrogenic effect of vaginal estriol has been reached in the vagina by a dose of only 30 µg estriol. In contrast to higher doses of vaginal estriol however, 30 µg/day estriol is not associated with systemic effects. Similarly, the use of 0.5 mg vaginal estriol twice a week instead of daily has been said to largely attenutate the systemic effects of estriol. Whereas oral estriol results in high levels of estriol conjugates which greatly exceed those of unconjugated estriol, vaginal estriol has been found to produce levels of unconjugated estriol and estriol conjugates that are similar.