Selecting constant serum estradiol levels achieved by vaginal rings.

Prolonged, constant, systemic administration of estradiol-17 beta is useful for research and clinical purposes. Sustained systemic administration of estradiol-17 beta can be accomplished by means of estradiol-17 beta-containing polydimethylsiloxane vaginal rings. The ability to preselect a specific circulating serum level of estradiol-17 beta from several possible levels using estradiol-17 beta vaginal rings would be advantageous. In the present study, the author examined the effects of changes in the surface area and estradiol-17 beta content of estradiol-17 beta vaginal rings on the resulting serum levels of estradiol-17 beta. During three months of estradiol-17 beta vaginal ring exposure, the average serum levels of estradiol-17 beta produced were 53 +/- 10 pg/mL with a 100-mg estradiol-17 beta vaginal ring, 81 +/- 7 pg/mL with a 200-mg estradiol-17 beta vaginal ring, and 152 +/- 14 pg/mL with a 400-mg estradiol-17 beta vaginal ring. When compared with levels of estradiol-17 beta observed in normal menstrual cycles, the levels obtained with the 100-mg estradiol-17 beta vaginal ring, 200-mg estradiol-17 beta vaginal ring, and 400-mg estradiol-17 beta vaginal ring correspond to early follicular phase, midfollicular phase, and complete menstrual cycle, respectively. The author concludes that stable circulating levels of estradiol-17 beta resulting from estradiol-17 beta vaginal ring administration resemble estradiol-17 beta levels characteristic of specific phases of the normal menstrual cycle. Therefore, estradiol-17 beta administration by estradiol-17 beta vaginal ring may be helpful for research and clinical applications.