Hormone-releasing silicone-rubber intrauterine contraceptive devices. Effect of incorporation of various compounds on intrauterine contraceptive devices in rats.

Intrauterine devices (IUD's) containing 0, 5, or 10 per cent by weight of progesterone, melengestrol acetate (MGA), norethindrone, norgestrel, medroxyprogesterone acetate, isoxsuprine, or R2323 or wound with fine copper wire were placed in one or both horns of cycling female rats. All the progestins improved retention of the silicone-rubber IUD's to some degree. The effects of these compounds on the estrous cycle, mating, ovulation, fertilization, tubal transport, and implantation varied among the compounds. Effects were local or systemic, depending upon the amount and the drug. Uterine motility studies showed clearly that 5 per cent MGA decreased uterine motility; however, no consistent results could be obtained using the other compounds in the same in vivo system.