Selection of steroids for incorporation into silastic intrauterine devices

Abstract

Progesterone, five synthetic progestins and one non-steroidal uterine relaxant were incorporated into silastic lUD's at levels at 5 and 10% total weight of the device in an effort to increase efficacy and decrease the rate of expulsion of the devices. Initial studies in rodents indicated that all compounds had some effect, the synthetic progestins being best. Five per cent devices did not inhibit mating while 10% did. The rate of release of four synthetic steroids was determined in rats, and that of medroxyprogesterone acetate in patas and rhesus monkeys as well. This latter steroid has been incorporated into IDD's (75–150 mg total dose) which have been used in women with very promising results. Two additional synthetic progestins, norgestrel and norethindrone, as well as Provera are being used in baboon IUD's with only Provera enhancing retention. The effect of daily microgram release rates of Provera on the menstrual cycle and perineal swelling is variable and reversible with removal of the device.