Development of a vaginal ring for achieving physiologic levels of 17 beta-estradiol in hypoestrogenic women.

The ability of polysiloxane vaginal rings containing 17 beta-Estradiol (E2) to deliver E2 into the systemic circulation at a steady rate over long periods of time was evaluated in castrate and postmenopausal volunteers. Standard laminar designs, used to release contraceptive gestagens, deliver low levels of E2 (about 50 pg/ml) and only for 1 month. With a modified design, E2 levels of 109 to 159 pg/ml were maintained for at least 3 months, and circulating gonadotropins were suppressed to values approaching the premenopausal range. This homogeneous design provides for physiologic replacement of E2 as well as a practical research tool for studying chronic effects of E2 in human subjects.